Commonwealth Trawl and Scalefish Hook Sectors

Chapter 9: Commonwealth Trawl and Scalefish Hook sectors

F Helidoniotis, T Emery, J Woodhams and R Curtotti

FIGURE 9.1 Relative fishing intensity (a) in the Commonwealth Trawl Sector and (b) by Danish-seine operations, 2018–19 fishing season

(a)

(b)

FIGURE 9.2 Relative fishing intensity in the Scalefish Hook Sector, 2018–19 fishing season

Trawler
Lee Georgeson, ABARES

TABLE 9.1 Status of the Commonwealth Trawl and Scalefish Hook sectors
Status20172018Comments
Biological status Fishing mortality BiomassFishing mortalityBiomass
Blue-eye trevalla (Hyperoglyphe antarctica)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

CPUE for the slope population is between the limit and target reference points.

Fishing mortality is below the most recent RBC.

Blue grenadier (Macruronus novaezelandiae)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Estimated spawning biomass was above the target reference point.

Total removals have remained below the long-term RBC.

Blue warehou (Seriolella brama)UncertainOverfishedUncertainOverfished

Total removals are above the incidental catch allowance.

No evidence that the stock is rebuilding.

Deepwater sharks, eastern zone (multiple species)Not subject to overfishingUncertainUncertainUncertain

Multispecies nature of stock makes CPUE unreliable as the index of abundance. Uncertain how catch may impact biomass.

Deepwater sharks, western zone (multiple species)Not subject to overfishingUncertainUncertainUncertain

Multispecies nature of stock makes CPUE unreliable as the index of abundance. Uncertain how catch may impact biomass.

Eastern school whiting (Sillago flindersi)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

2017 estimate of biomass is above the target reference point. Total removals since 2009 have been below the RBC.

Flathead (Neoplatycephalus richardsoni and 4 other species)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Recent estimates of biomass are above the target reference point, and current catches are below the RBC.

Gemfish, eastern zone (Rexea solandri)UncertainOverfishedUncertainOverfished

Biomass is below the limit reference point. Uncertainty remains around total fishing mortality and rebuilding to the limit reference point within the specified time frame.

Gemfish, western zone (Rexea solandri)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Estimated spawning biomass is above the target reference point. Catches have been stable in recent years and below the RBC.

Gulper sharks (Centrophorus harrissoni, C. moluccensis, C. zeehaani)UncertainOverfishedUncertainOverfished

Populations are below the limit reference point, and fishing mortality is uncertain, despite low landed catch and protection from closures.

Jackass morwong (Nemadactylus macropterus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Accepting the ‘regime shift’ scenario for the eastern stock, estimates of spawning biomass depletion are above the limit reference point.

Estimates of spawning biomass for the western stock are above the target reference point. Total removals in both east and west remain below the RBC.

John dory (Zeus faber)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Catches and fishing mortality rates are low. Assessment indicates that biomass is above the limit reference point.

Mirror dory (Zenopsis nebulosa)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Recent CPUE is above the limit reference point.

Total mortality is below RBCs for eastern and western stocks.

Ocean jacket (Nelusetta ayraud)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

History of stable CPUE, increasing in recent years.

Ocean perch (Helicolenus barathri, H. percoides)UncertainNot overfishedNot subject to overfishingNot overfished

Recent CPUE (including discards) is above the limit reference point for both species. Total fishing mortality is below the RBC.

Orange roughy, Cascade Plateau (Hoplostethus atlanticus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Most recent estimate of spawning biomass (2011) is above the target reference point. Catches since the last estimate have been below the RBC.

Orange roughy, eastern zone (Hoplostethus atlanticus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Most recent stock assessment estimated biomass to be between the limit and target reference points. Fishing mortality has not exceeded the RBC.

Orange roughy, southern zone (Hoplostethus atlanticus)Not subject to overfishingOverfishedNot subject to overfishingOverfished

Most recent assessment estimated that stock is depleted; stock is classified as overfished. Negligible catches. Closure of most areas deeper than 700 m. No updated stock assessment.

Orange roughy, western zone (Hoplostethus atlanticus)Not subject to overfishingOverfishedNot subject to overfishingOverfished

Most recent assessment estimated that stock is depleted; stock is classified as overfished. Negligible catches. Closure of most areas deeper than 700 m. No updated stock assessment.

Smooth oreodory, Cascade Plateau (Pseudocyttus maculatus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Low recent catches. CPUE is above the target reference point.

Smooth oreodory, non–Cascade Plateau (Pseudocyttus maculatus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Closure of most areas deeper than 700 m. Recent CPUE is above the target reference point. New tier 5 assessment indicates catch is below levels that would result in depletion.

Other oreodories (Allocyttus niger, Neocyttus rhomboidalis, A. verrucosus, Neocyttus spp.)UncertainNot overfishedUncertainNot overfished

Recent CPUE is stable, near the target reference point. Total fishing mortality exceeds the RBC. Closure of most areas deeper than 700 m.

Pink ling (Genypterus blacodes)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Fishing mortality for both stocks is below the RBC. Western stock is above target. Biomass of eastern stock is between the limit and target reference points.

Redfish (Centroberyx affinis)UncertainOverfishedUncertainOverfished

Biomass is below the limit reference point. It is unclear if total removals are above the level that will allow rebuilding.

Ribaldo (Mora moro)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Standardised CPUE has remained stable and above the target reference point. Catches have remained below RBCs.

Royal red prawn (Haliporoides sibogae)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Recent average CPUE is above the limit reference point, and total fishing mortality has been below the RBC in recent years.

Silver trevally (Pseudocaranx georgianus)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Recent average CPUE is above the limit reference point, and recent total fishing mortality has been below the RBC.

Silver warehou (Seriolella punctata)Not subject to overfishingNot overfishedNot subject to overfishingNot overfished

Spawning biomass is between the limit and target reference points. Total removals are below the RBC.

Economic statusNER in the CTS rose to reach $4.0 million in 2016–17, largely driven by lower operating costs. Preliminary estimates from the survey suggest that NER were –$0.17 million in 2017–18. This negative result is driven by lower forecast income and higher forecast operating costs.

Notes: CPUE Catch-per-unit-effort. CTS Commonwealth Trawl Sector. NER Net economic returns. RBC Recommended biological catch.

Flathead
Heather Patterson, ABARES

[expand all]

9.1 Description of the fishery

Area fished

The Commonwealth Trawl Sector (CTS) of the Southern and Eastern Scalefish and Shark Fishery (SESSF) extends from east of Sydney southwards through Bass Strait and around Tasmania to Cape Jervis in South Australia, where it abuts the Great Australian Bight Trawl Sector (GABTS; Chapter 11; Figure 9.1). To the north, the CTS adjoins the East Coast Deepwater Trawl Sector (Chapter 10) at 24°30'S off Queensland. From the same boundary, the Scalefish Hook Sector (SHS) extends around south-eastern Australia to the border of South Australia and Western Australia (Figure 9.2). The SHS is managed as part of the Gillnet, Hook and Trap Sector (GHTS) of the SESSF, but is reported in this chapter because it shares many target species with the CTS. The CTS and the SHS are major domestic sources of fresh fish for the Sydney and Melbourne markets. In contrast to several Commonwealth fisheries, CTS and SHS landings are rarely exported to overseas markets.

The distributions of many CTS and SHS stocks do not lie wholly within the jurisdiction of Commonwealth waters, because stocks also straddle inshore state waters. Under Offshore Constitutional Settlement arrangements, some states have ceded control of SESSF quota-managed species to the Australian Government. In these cases, catches in state waters by Australian Government–endorsed vessels are debited against their SESSF total allowable catch (TAC) limits. However, New South Wales retains jurisdiction over non-trawl fishers along the New South Wales coastline out to 80 nautical miles (nm) offshore, and over trawl fishers out to 80 nm offshore north of Sydney and out to 3 nm offshore south of Sydney.

Fishing methods and key species

The CTS and the SHS are multigear and multispecies fisheries, targeting a variety of fish and shark stocks using different gear types in different areas or depth ranges. Effort in these fisheries is widely distributed, but, since 2005—after the closure to trawling of most SESSF waters deeper than 700 m—effort has become increasingly concentrated on the shelf rather than on the slope or in deeper waters.

The CTS predominantly uses demersal otter trawl and Danish-seine fishing methods. Pair trawling and midwater trawling methods are also permitted under the SESSF management plan, but are rarely used. The SHS employs a variety of longline and dropline hook fishing methods, some of which are automated.

Management arrangements

Management of the CTS and the SHS in the 2018–19 season followed the SESSF harvest strategy framework (HSF; AFMA 2017a) (see Chapter 8). The HSF was updated in 2019 (AFMA 2019). Stocks in both the CTS and the SHS are managed under individual transferable quotas (ITQs) for key commercial species. TACs are set for quota species for each fishing season and allocated to quota holders. All TACs are determined by the Australian Fisheries Management Authority (AFMA) Commission each year. To help reduce assessment and management costs, and create greater certainty for industry, use of multiyear TACs (MYTACs) has been increasing since 2009–10. The AFMA Commission determines TACs each year, irrespective of whether stocks are under a MYTAC. A decision-tree approach (replacing the use of ‘breakout rules’) specifies the circumstances for reviewing the stock during the MYTAC period, and allows for management intervention in the event of unexpected deviation from predicted trends in stock size or response to fishing (AFMA 2018b). Twenty stocks were under MYTACs across the SESSF in 2018–19 (AFMA 2018b); 15 of these are reported in this chapter.

A total of 19,268 t of quota was available across the stocks assessed in this chapter for the 2018–19 fishing season (1 May 2018 – 30 April 2019). This was a decrease of 114 t from 2017–18 (Table 9.2). A small proportion of this quota (409 t) was allocated as ‘incidental catch allowances’ to allow unintentional catches of eastern gemfish (Rexea solandri), blue warehou (Seriolella brama), orange roughy (Hoplostethus atlanticus—southern and western zones1) and redfish (Centroberyx affinis). Most of the overall quota decrease between 2017–18 and 2018–19 resulted from decreased TACs for silver trevally (Pseudocaranx georgianus; –306 t), flathead (Neoplatycephalus richardsoni and four other species; –205 t) and eastern school whiting (Sillago flindersi; –166 t). These decreases were partially offset by TAC increases for orange roughy eastern zone (+233 t) and john dory (Zeus faber; +88 t).

Fishing effort

In 2018–19, trawlers reported 54,298 hours of fishing effort—a slight decrease from the 57,747 hours in 2017–18 (Figure 9.3; Table 9.2). The number of active trawlers remained stable, with 32 active in both 2017–18 and 2018–19 (Table 9.2). Danish-seine effort increased from 9,965 shots in 2017–18 to 10,430 shots in 2018–19, and the number of vessels increased from 18 in 2017–18 to 19 in 2018–19. Fishing effort in the SHS increased slightly from 3.547 million hooks in 2017–18 to 3.733 million hooks in 2018–19 (Figure 9.4; Table 9.2).

Catch

Total catch (catch disposal records) for quota stocks and non-quota stocks (gulper shark—Centrophorus spp., and ocean jacket—Nelusetta spp.) for both sectors was 8,454 t in 2018–19; 7,574 t was from CTS quota stocks, 740 t was from GHTS quota stocks, and 140 t was ocean jacket (including leather jacket—N. ayraud). The total landed catch (including catch of all other species) of 8,454 t was a decrease on the total landed catch of 8,631 t in 2017–18.

The total catch reported in logbooks, of all species managed under TACs from the CTS in 2018–19, was 7,574 t. Flathead (tiger flathead), blue grenadier (Macruronus novaezelandiae), pink ling (Genypterus blacodes), eastern school whiting and orange roughy accounted for approximately 72% of the catch (Table 9.2). Flathead catches have decreased in recent years, from 2,873 t in 2016–17 to 2,434 t in 2017–18 and then 2,035 t in 2018–19. Catches of blue grenadier increased from 1,619 t in 2017–18 to 1,804 t (representing around 24% of the available quota) in 2018–19. The total scalefish landings from the GHTS (of which the SHS comprises the primary component reported in this chapter) in the 2018–19 fishing season were estimated to be 740 t, higher than the 651 t landed in the 2017–18 fishing season.

The term ‘landed catch’ refers to catch that is reported at the port; it excludes discards. Data on discards are collected for the SESSF as part of the Integrated Scientific Monitoring Program. The discard data, collected over the previous four years, were converted into a weighted average to estimate discards for the current fishing season (see Table 41 in Castillo-Jordán et al. 2018). AFMA use a four-year weighted average of discards when determining a TAC from the recommended biological catch (RBC) (AFMA 2017c) and, for consistency, the same estimates are included when reporting on stock status.

The terms ‘agreed TAC’ and ‘actual TAC’ are both referred to in this chapter. In general, the agreed TAC is estimated by subtracting the discount factor, state catches and discards from the RBC (AFMA 2016b). The actual TAC is the agreed TAC adjusted for any overcaught or undercaught TAC from the previous season.

Information on gross value of production (GVP) for the 2018–19 season was not available at the time of publication. During 2017–18, scalefish catches in the CTS accounted for 55% of the GVP of the SESSF. Scalefish GVP in the CTS decreased by 7%, from $40.01 million in 2016–17 to $37.09 million in 2017–18. The GVP in the SHS decreased by 25%, from $6.41 million in 2016–17 to $4.78 million in 2017–18. Overall, the total scalefish GVP in 2017–18 for both sectors was $41.86 million (Table 9.2).

Flathead (tiger flathead and other flathead species) contributed $15.78 million to GVP in 2017–18, the most of any scalefish (Table 9.2); this was a decrease of 14% from $18.40 million in 2016–17. The value of pink ling catch decreased by 3% in 2017–18 to $5.05 million. The value of blue-eye trevalla (Hyperoglyphe antarctica) catch (largely caught in the SHS) decreased by 27% in 2017–18 to $2.94 million. Blue grenadier accounted for $2.80 million in 2017–18, which was 10% higher than in 2016–17 ($2.54 million) but 84% lower than in 2012–13 in real terms.

FIGURE 9.3 Total catch and fishing effort for the CTS, 1985 to 2018

Source: AFMA

FIGURE 9.4 Total catch and fishing effort for the SHS, 2000 to 2018

Source: AFMA

TABLE 9.2 Main features and statistics for the CTS and the GHTS a

Fishery statistics b

2017–18 fishing season

2018–19 fishing season

Stock

TAC
(t) c

Catch (t)
(CTS, GHTS)

GVP

(2017–18)

TAC
(t) c

Catch (t)
(CTS, GHTS)

Blue-eye trevalla

458

327 (51,276)

$2.94 million

462

373.6 (31.3, 342.3)

Blue grenadier

8,765

1,624 (1,619, 5)

$2.80 million

8,810

1,808 (1,804, 4)

Blue warehou

118 d

25 (24, 0.6)

$0.11 million

118 d

54.2 (54.2, <1)

Deepwater sharks, eastern zone

46

23 (22, 0.7)

na

23

19.8 (19, 0.8)

Deepwater sharks, western zone

215

80 (79, 0.6)

na

264

78.7 (78, 0.7)

Eastern school whiting

986

736 (736, 0)

$2.27 million

820

537 (537.1, 0)

Flathead (tiger flathead and several other species)

2,712

2,436
(2,434, 1.4)

$15.78 million

2,507

2,036
(2,034.9, 0.9)

Gemfish, eastern zone

100 d

30 (27, 3)

$0.07 million

100 d

39.1 (33.8, 5.3)

Gemfish, western zone e

199

77 (76.7, <1)

$0.17 million

200

78.5 (78.5, <1)

Jackass morwong

513

185 (182, 3)

$0.45 million

505

186 (183.9, 2.3)

John dory

175

83 (83, <1)

$0.82 million

263

61.8 (61.8, <1)

Mirror dory

235

220 (220, <1)

$0.58 million

253

117.5 (117.5, <1)

Ocean perch

190

169 (150, 19)

$0.04 million

241

195 (168.7, 26.3)

Orange roughy, Cascade Plateau

500

0

0

500

0

Orange roughy, eastern zone

465

297

$2.30 million

698

855.8

Orange roughy, southern zone

66 f

53

$0.18 million

84 f

78.5

Orange roughy, western zone

60 d

23

$0.84 million

60 d

19

Smooth oreodory, Cascade Plateau

150

0

0

150

0

Smooth oreodory, non–Cascade Plateau

90

55

$0.14 million

90

74.1

Other oreodories

128

106 (105, 1)

$0.10 million

185

104 (102, 1.5)

Pink ling

1,154

1,036 (740, 297)

$5.05 million

1,117

952 (645.5, 306.9)

Redfish

100 d

26 (26, <1)

$0.11 million

100 d

30.8 (30.8, <1)

Ribaldo

355

95 (55, 40)

$0.22 million

430

107.3 (60, 47.3)

Royal red prawn

384

222 (222, 0)

$0.88 million

381

147 (147, 0)

Silver trevally

613

55 (55, <1)

$0.23 million

307

8.3 (8.3, <1)

Silver warehou

605

432 (432, <1)

$0.57 million

600

352 (352, <1)

Non-quota species

TAC
(t) c

Catch (t)
(CTS, GHTS)

GVP

(2017–18)

TAC
(t) c

Catch (t)
(CTS, GHTS)

Gulper sharks

na

0.35 (0.27, 0.9)

na

na

0.38 (0.38, 0)

Ocean jacket g

na

216

$0.26 million

na

140

Total

19,382

8,631

$41.86 million

19,268

8,454

Fishery-level statistics

Effort
Otter trawl
Danish-seine
Scalefish hook

57,747 trawl-hours
9,965 shots
3.547 million hooks

54,298 trawl-hours
10,430 shots
3.733 million hooks

Boat statutory fishing rights

57 trawl; 37 scalefish hook

57 trawl; 37 scalefish hook

Active vessels

32 trawl; 18 Danish-seine;
29 scalefish hook

32 trawl; 19 Danish-seine; 21 scalefish hook

Observer coverage
CTS
Auto-longline (scalefish)

Trawl: 212 fishing days
Danish-seine: 20 fishing days
26 sea-days

Trawl: 193 fishing days
Danish-seine: 27 fishing days
26 sea-days

Fishing methods

Trawl, Danish-seine, hook (dropline, demersal longline), trap (minor)

Primary landing ports

Eden, Sydney and Ulladulla (New South Wales); Hobart (Tasmania); Lakes Entrance and Portland (Victoria)

Management methods

Input controls: limited entry, gear restrictions, area closures
Output controls: TACs, ITQs, trip limits

Primary markets

Domestic: Sydney, Melbourne—fresh, frozen
International: minimal

Management plan

Southern and Eastern Scalefish and Shark Fishery Management Plan 2003

a The SHS is managed as part of the GHTS. b Fishery statistics are provided by fishing season, unless otherwise indicated. Fishing season is 1 May – 30 April. Value statistics are provided by financial year and were not available for the 2018–19 financial year at the time of publication. c TACs shown are the ‘agreed’ TACs. These may differ from ‘actual’ TACs, which may include undercatch and overcatch from the previous fishing season. Consequently, catch for some stocks may slightly exceed agreed TACs. d Incidental catch allowance. e Not including the Great Australian Bight Trawl Sector. f Total catch includes a 31 t incidental catch allowance and 53 t of target quota, resulting from apportioning quota from the orange roughy eastern zone stock to the Pedra Branca area, which is part of the southern zone but included in the eastern zone assessment. g Catch figures are combined for the trawl and non-trawl sectors.
Notes: CTS Commonwealth Trawl Sector. GHTS Gillnet, Hook and Trap Sector. ITQ Individual transferable quota. na Not available. SHS Scalefish Hook Sector. TAC Total allowable catch.

1 The orange roughy southern zone TAC contains both ‘incidental’ catch allowance and ‘target’ quota because quota is apportioned in accordance with the orange roughy eastern zone stock assessment. Orange roughy from Pedra Branca in the southern zone is included as part of the assessed eastern stock.

9.2 Biological status

Blue-eye trevalla (Hyperoglyphe antarctica)

Blue-eye trevalla (Hyperoglyphe antarctica)

Line drawing: FAO

Stock structure

In the 2018–19 fishing season, blue-eye trevalla was managed as a single biological stock in the SESSF. However, spatial heterogeneity in stock structure has been reported based on phenotypic variation in age and growth, otolith chemistry, and potential larval dispersal between regions around the south-east of Australia (Williams et al. 2017). Four geographically distinct subpopulations were proposed in the SESSF, with three in the CTS. These three subpopulations are interconnected through regional exchange of larvae (Williams et al. 2017). The results of the study by Williams et al. (2017) led to the decision by the South East Resource Assessment Group (SERAG) in November 2018 to assess the seamount and slope subpopulations as separate stocks for the 2019–20 fishing season (AFMA 2018c).

Catch history

Blue-eye trevalla catch peaked at more than 800 t in 1997 (Figure 9.5). Commonwealth-landed catch in the 2018–19 fishing season was 373.6 t. State catch was 17.5 t, and weighted average discards between 2014 and 2017 were 0.1 t (Castillo-Jordán et al. 2018). For the 2018–19 fishing season, catch and discards combined were 373.7 t.

FIGURE 9.5 Blue-eye trevalla annual catches (CTS, SHS and states) and fishing season TACs, 1997–2018

Notes: TAC Total allowable catch. Data for 2018 do not include discards and state catch.
Sources: Sporcic 2018; AFMA catch disposal records (2018 data)

Stock assessment

The management of the blue-eye trevalla stock for the 2018–19 fishing season was based on the standardised catch-per-unit-effort (CPUE) and associated tier 4 analyses undertaken by Haddon (2017b)(Figure 9.6). A CPUE series was standardised using a combination of auto-longline (2002–2016) and dropline (1997–2006) data from zones 20–50 and the eastern seamounts (Haddon 2017b), and then the tier 4 harvest control rules from the SESSF HSF (AFMA 2017a) were applied. This generated a single-year RBC of 481.6 t (Haddon 2017b), with the AFMA Commission subsequently determining a TAC of 462 t for the 2018–19 season.

In 2018, a new assessment split the stock into two regions (slope and seamount populations), with each assessed separately to inform the determination of an RBC for the 2019–20 fishing season. A tier 4 assessment was completed for the slope stock and a tier 5 assessment for the seamount stock (due to poor CPUE data) (AFMA 2018c).

The slope assessment suggested that the previous steep decline in CPUE (2013–2016) had levelled out and that CPUE remained between the target and limit reference points as defined by the SESSF HSF (AFMA 2017a). As previously noted by Haddon (2016), this assessment has various sources of uncertainty. Two factors that could influence catch rates and fishing behaviour, resulting in a low bias for CPUE, include the presence of killer whales (orcas—Orcinus orca) near fishing operations and resulting depredation, and exclusions from historical fishing grounds following closures implemented to rebuild gulper shark stocks (AFMA 2014b). The previous analysis (Haddon 2016) did not detect large effects on CPUE due to the closures, but uncertainty remains about the effect of whale depredation on CPUE.

The age-structured stock reduction analysis undertaken for the seamount population predicted that constant catches of around 25 t for lower productivity scenarios and 48 t for higher productivity scenarios would lead to relative stability in depletion. Although highly uncertain, a maximum sustainable yield (MSY) analysis of the seamount catch generated an MSY of about 45–50 t, with a depletion estimate of about 33% of the unfished biomass (0.33B0). It was predicted, based on the catch MSY, that constant catches of 40 t or less would lead to the mean and median depletion levels remaining stable at the proxy of 0.48B0 (AFMA 2018a, e).

The application of the SESSF tier 4 harvest control rule to the outputs of the standardised CPUE series for the slope stock generated a single-year RBC of 439 t. SERAG agreed to an RBC of 36 t for the seamount stock, based on the output of the age-structured stock reduction analysis and catch MSY analysis for the 2019–20 fishing season (AFMA 2018a, e).

FIGURE 9.6 Standardised auto-longline and dropline CPUE index for blue-eye trevalla to the east and west of Tasmania, 1997–2017

Note: CPUE Catch-per-unit-effort.
Source: Sporcic 2018

Stock status determination

The four-year average CPUE (2013–2016) from the analysis undertaken by Haddon (2017b) is between the limit and the target reference points defined by the SESSF HSF. The blue-eye trevalla stock is therefore classified as not overfished.

In the 2018–19 fishing season, catch and discards combined were 373.6 t, which is below the RBC (481.6 t). This indicates that, if the fishing mortality in 2018–19 is maintained, the stock is unlikely to be depleted to a level below the biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Blue grenadier (Macruronus novaezelandiae)

Blue grenadier (Macruronus novaezelandiae)

Line drawing: Rosalind Poole

Stock structure

Blue grenadier is assessed as a single stock. There are two discernible subfisheries: the winter spawning fishery off western Tasmania and the widely spread catches of the non-spawning fishery.

A stock structure study using otolith chemistry and otolith shape (Hamer et al. 2009) has proposed that more than one stock of blue grenadier is fished in the SESSF. Specifically, the otolith indicators provided support for separate stocks of blue grenadier being fished by the GABTS and the CTS of the SESSF. The study also indicated that blue grenadier from the western Tasmanian and eastern Bass Strait regions of the CTS were unlikely to be part of one highly mixed south-eastern Australian stock. However, this stock structure hypothesis has not been implemented into management and is not currently considered in the application of the SESSF HSF for the species.

Catch history

The blue grenadier fishery started in the early 1980s, and between 1985 and 1995 mainly targeted non-spawning fish. From 1995 onwards, a fishery developed on spawning aggregations, and total catches increased to average around 8,000 t from 1999 to 2003 (Figure 9.7). Catches since then have varied in response to changes in the TAC and the influence of market conditions. The average state catch was 0.1 t, and the weighted average discards between 2014 and 2017 were 689.08 t (Castillo-Jordán et al. 2018). Commonwealth-landed catch in the 2018–19 fishing season was 1,804.6 t.

FIGURE 9.7 Blue grenadier annual catches (CTS and SHS) and fishing season TACs, 1979–2018

Notes: TAC Total allowable catch. Data for 2018 do not include discards.
Sources: Castillo-Jordán & Tuck 2018; AFMA catch disposal records (2018 data)

Stock assessment

Blue grenadier in Commonwealth fisheries is managed as a tier 1 stock under the SESSF HSF (AFMA 2017a). The stock is considered to be a key commercial stock, and has a target reference point of 48% of the unfished spawning stock biomass (0.48SB0; Figure 9.8) (Castillo-Jordán & Tuck 2018).

The assessment underpinning the management of blue grenadier for the 2018–19 season is the tier 1 assessment of Tuck (Tuck 2013). The assessment estimated that the spawning biomass depletion for 2012 was approximately 77% (0.77SB0), and predicted the depletion level for 2014 to be approximately 94% (0.94SB0). The 2013 assessment produced an RBC of 8,138 t and an average three-year (2014–2016) RBC of 8,810 t (Tuck 2013). In 2015, AFMA recommended an RBC of 8,810 t, which continued into the 2018–19 season (AFMA 2018b). AFMA also extended the three-year MYTAC that started in 2014–15 for a fifth year, into the 2018–19 season (AFMA 2018b).

An updated tier 1 assessment (Castillo-Jordán & Tuck 2018) indicated that the predicted spawning biomass depletion for 2019 would be 1.22SB0. This is above the target 0.48SB0, and higher than the level predicted for 2019 by the 2013 assessment (0.9–1.0SB0).

FIGURE 9.8 Estimated female spawning biomass for blue grenadier, 1973–2017

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Castillo-Jordán & Tuck 2018

Stock status determination

The assessment underpinning the management of blue grenadier for the 2018–19 season (Tuck 2013) indicated that spawning biomass would be above the target reference point if recommended catches were taken. An updated assessment in 2018 confirmed that biomass was indeed above the target reference point. As such, the stock remains classified as not overfished.

For the 2018–19 fishing season, the landed catch and discards combined were 2,497 t, which is below the RBC of 8,810 t calculated in 2013 (Tuck 2013). This level of catch is unlikely to deplete the stock to a level below the biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Blue warehou (Seriolella brama)

Blue warehou (Seriolella brama)

Line drawing: Rosalind Poole

Stock structure

Blue warehou is assumed to have separate eastern (southern New South Wales to eastern Tasmania) and western (western Tasmania to western Victoria) stocks (Morison et al. 2013). Although these stocks are assessed separately, status is reported for a combined stock, reflecting the unit of management.

Catch history

Landings of blue warehou peaked in 1991 at 2,478 t (Figure 9.9). Catch has since declined, with less than 500 t landed per year since 2000. A rebuilding strategy that established blue warehou as an incidental catch-only species was first implemented in 2008, with the objective of rebuilding stocks by 2024. While landed catches decreased to just 2 t in 2015–16, they have since increased to 54.2 t in 2018–19. Meanwhile, discards have significantly increased from 6.1 t in 2016 to 146.2 t in 2017. State catch was 7.6 t, and weighted average discards between 2014 and 2017 totalled 80.7 t (Castillo-Jordán et al. 2018). In 2018–19, catch and discards combined (using the weighted average discards) were 142.5 t.

The increase in the discard estimate was largely driven by very small fish being caught by Danish-seiners in eastern Bass Strait (AFMA 2018a). Note, however, that the discard estimate for 2017 is very uncertain because of under reporting and extrapolation of the data (Paul Burch [CSIRO], 2019, pers. comm.). In 2018–19, catch and discards combined were 134.9 t, which was above the 2018–19 incidental catch allowance of 118 t.

FIGURE 9.9 Blue warehou annual catches (CTS, SHS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2013–2018 do not include discards and state catch.
Sources: Haddon 2013; AFMA catch disposal records (2013–2018 data)

Stock assessment

Blue warehou was managed as a tier 4 stock under the SESSF HSF (AFMA 2017a), but it has been classified as overfished since 1999 and is currently managed under a rebuilding strategy (AFMA 2014a) with an incidental catch allowance of 118 t.

The standardised CPUE series of both the eastern and western blue warehou stocks declined after the reference period of 1986–1995 (Haddon 2013). For the eastern stock, CPUE has been below the limit reference point since 1998. For the western stock, CPUE has been below the limit reference point for most years since 1995, except for 1998 and 2005 (Figures 9.10 and 9.11). Although each CPUE series is presented as a continuous line, they should be interpreted in two separate periods for each stock (Figures 9.10 and 9.11). The CPUE for the reference period is the relative abundance when there was no quota management or rebuilding strategy in place. The period after 1995 includes the period of quota-based management measures and, from around 2000 onwards, efforts to limit targeting. Consequently, CPUE outside the reference period may not be an accurate indicator of biomass.

In 2008, a rebuilding strategy was implemented for blue warehou (subsequently revised in 2014) with the goal of rebuilding stocks to the limit reference point by or before 2024 (one mean generation time plus 10 years). Initially, the 2008 strategy implemented a rebuilding time frame of one mean generation time only (which is approximately six years to 2014 [AFMA 2014a]). However, when assessed in 2013, the standardised CPUE remained below the CPUE expected if the biomass was above its limit reference point, suggesting that the stock was not likely to rebuild by 2014. In February 2015, the species was listed as conservation-dependent under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act; Department of the Environment 2015).

Under the rebuilding strategy, targeted fishing for blue warehou is not permitted. AFMA set an annual incidental catch allowance of 133 t for blue warehou for 2011–12, which was reduced to 118 t in 2012–13 and applied to subsequent fishing seasons. The incidental catch allowance includes triggers of 27 t in the east and 91 t in the west. These triggers are intended to alert AFMA and SERAG if the ratio of catches in the east and the west change substantially, and result in increased reporting requirements for commercial fishers encountering blue warehou (AFMA 2014a). In September 2015, the Shelf Resource Assessment Group (ShelfRAG) discussed whether the rebuilding strategy for blue warehou was meeting its objectives (AFMA 2015c), and noted a lack of signs of recovery and potential range contraction. It also noted that current SESSF catches, even with low recruitment, should not be impeding recovery.

AFMA has also introduced a move-on provision to reduce the risk of large catches of blue warehou in the 2019–20 fishing season. Fishers that catch more than 200 kg of blue warehou in a single shot (retained or discarded) must not fish within 3 nm of the previous shot for 24 hours (AFMA 2019).

FIGURE 9.10 Standardised CPUE for blue warehou, western stock, 1986–2012

Notes: CPUE Catch-per-unit-effort. CPUE outside the reference period (1986–1995) is unlikely to accurately reflect biomass.
Source: Haddon 2013

FIGURE 9.11 Standardised CPUE for blue warehou, eastern stock, 1986–2012

Notes: CPUE Catch-per-unit-effort. CPUE outside the reference period (1986–1995) is unlikely to accurately reflect biomass.
Source: Haddon 2013

Stock status determination

The most recent indicators of biomass (albeit uncertain and dated) indicated that blue warehou had been reduced to below the limit reference point. Given that there is no evidence to suggest that the stock is likely to have rebuilt to above this level, blue warehou remains classified as overfished.

Blue warehou is under a rebuilding strategy (AFMA 2014a), with an incidental catch allowance of 118 t. In 2018–19, catch and discards combined were 142.5 t, which was above the incidental catch allowance of 118 t. This incidental catch allowance is based on a statistical analysis undertaken by CSIRO that determined that 118 t of the 154 t of blue warehou caught in 2010 was unavoidable (AFMA 2014a). This level of unavoidable catch has provided the basis for subsequent incidental catch allowances set by AFMA. Therefore, while the incidental catch allowance was exceeded in 2018–19, there are no reliable indicators to determine whether the current level of fishing mortality will allow the stock to rebuild to above the limit reference point within a biologically reasonable time frame. An alternative index of abundance with which to assess status is a priority for this species, with new genetic approaches (for example, close kin) not reliant on CPUE being considered (AFMA 2018a). The fishing mortality of the stock is therefore classified as uncertain.

Deepwater sharks, eastern and western zones (multiple species)

Deepwater sharks, eastern and western zones (multiple species)

Deepwater sharks, eastern and western zones (multiple species)

Line drawing: FAO and Anne Wakefield

Stock structure

The deepwater shark stock comprises multiple species of deepwater sharks, including dogfish (Squalidae), brier shark (Deania calcea), platypus shark (D. quadrispinosa), Plunket’s shark (Centroscymnus plunketi), roughskin shark (species of Centroscymnus and Deania), ‘pearl shark’ (D. calcea and D. quadrispinosa), black shark (Centroscymnus species) and lantern shark (Etmopterus spp.) (Klaer et al. 2014). Identification of some sharks is difficult. Black shark and Plunket’s dogfish are both possibly confounded with the roughskin shark group. The pearl shark group is a combination of the brier and platypus sharks (Haddon 2013).

Little is known about the stock structure of these deepwater sharks. They are benthopelagic species that have been sampled in oceanic environments over the abyssal plains, and are distributed widely across ocean basins, and along the middle and lower continental shelves. The eastern zone extends from New South Wales, around the Tasmanian east coast and up the Tasmanian west coast to 42°S, including Bass Strait to 146°22'E. The western zone includes the remainder of the SESSF, around to Western Australia. This boundary cuts across deepwater shark trawl grounds. The most likely biological boundary for these species is the biogeographical boundary between the two systems dominated by the Eastern Australian Current and the Leeuwin Current off the south coast of Tasmania (Morison et al. 2013). For the purposes of these status reports, the eastern zone is treated as one stock, and the western zone is treated as another stock.

Catch history

TACs for the deepwater shark multispecies stock are set separately for the eastern and western zones, and cover all deepwater shark species taken in those zones. The eastern deepwater shark fishery started in about 1990. Landed catches increased steadily to around 200 t in 1998, with a single higher peak of about 330 t in 1996, before decreasing steadily to around 25 t in recent years (Figure 9.12). The eastern catch in the 2018–19 season was 19.8 t. The western catch followed a similar trend, starting in 1993; it increased to a peak of about 400 t in 1998, before decreasing steadily to less than 10 t in 2007. Catch in the 2018–19 fishing season was 78.7 t (Figure 9.13). Weighted average discards were 38.8 t (eastern) and 76.08 t (western) (Castillo-Jordán et al. 2018). State catch is not known.

In 2018–19, platypus sharks (mixed), roughskin dogfishes (mixed), longsnout dogfish and sleeper sharks (mixed) accounted for most of the catch in the east; and platypus sharks (mixed), longsnout dogfish and sleeper sharks (mixed) accounted for most of the catch in the west.

FIGURE 9.12 Deepwater shark annual catches (CTS) and fishing season TACs, eastern zone, 1992–2018

Notes: TAC Total allowable catch. Data for 2018 include catch disposal records from the CTS and the SHS.
Source: Sporcic 2018; AFMA catch disposal records (2018 data)

FIGURE 9.13 Deepwater shark annual catches (CTS) and fishing season TACs, western zone, 1986–2018

Notes: TAC Total allowable catch. Data for 2018 include catch disposal records from the CTS and the SHS.
Source: Sporcic 2018; Sporcic & Haddon 2018a; AFMA catch disposal records (2018 data)

Stock assessment

Both eastern and western deepwater shark stocks are managed as tier 4 stocks under the SESSF HSF (AFMA 2017a). Analyses by Haddon and Sporcic (2017b) underpinned the management of eastern and western deepwater shark for the 2018–19 season.

The RBC for the eastern deepwater shark stock was 9 t (Haddon & Sporcic 2017b). AFMA implemented a TAC of 23 t (AFMA 2018e) as a result of the large change–limiting rule within the harvest strategy that aims to avoid large changes in TACs between years. The TAC for the previous year was 46 t. CPUE was very near the limit reference point identified by Haddon and Sporcic (2017b) and remains at similar levels in the latest analyses (Sporcic & Haddon 2018a).

The RBC for the western deepwater shark stock was 313 t (Haddon & Sporcic 2017b). The recent average CPUE was above the target reference point in Haddon and Sporcic (2017b) and remains at similar levels in the latest analyses (Sporcic & Haddon 2018a).

Deepwater closures may differentially affect the CPUE of deepwater sharks in the eastern and western zones because of the different fishing conditions between the two areas. In the western zone, the CPUE remains high; however, in the eastern zone, CPUE has declined (Haddon & Sporcic 2017b).

There have been ongoing issues with producing reliable standardised CPUE series for these stocks to support the tier 4 harvest control rule of the harvest strategy, and currently there is limited scope to improve these data. The lack of historical data, together with the multispecies nature of the stock and difficulties in species identification by fishers, mean that the standardised CPUE series may not be a reliable index of abundance for the stock or its component species.

Deepwater sharks are mobile animals that cover a broad range of depths (Morison et al. 2013). A significant area of the fishery—around 54% of the area where catch of this stock was previously taken—has been closed as part of the 700 m depth closures to manage orange roughy stocks. Recently, part of the closure was reopened to allow deepwater trawling for western stocks. However, if 25 t of orange roughy is taken, then the closure is reinforced (AFMA 2017d). These closures may offer a level of protection to the deepwater shark stocks, if they are similarly distributed across the open and closed areas.

Stock status determination

The deepwater shark stocks are both multispecies stocks, and robust data on historical catch composition and discards are lacking. Further, CPUE is unlikely to provide a reliable index of abundance for these stocks or their component species. As a result, the biomass levels of these stocks are classified as uncertain.

For the eastern stock, the landed catch and discards combined were 58.2 t, which is substantially above both the RBC (9 t) and the TAC (23 t). For the western stock, the landed catch and discards combined were 154.8 t, which is below the RBC of 313 t.

Although large areas are closed to fishing, which could provide some protection to the deepwater shark stocks, there is no reliable indication of biomass and therefore little confidence in a comparison of catch or fishing mortality with the RBC. On this basis, fishingmortality of the eastern and western deepwater shark stocks is classified as uncertain.

Eastern school whiting (Sillago flindersi)

Eastern school whiting (Sillago flindersi)

Line drawing: FAO

Stock structure

Eastern school whiting occurs from southern Queensland to western Victoria. Genetic studies have suggested two stocks in this range, with the division between a ‘northern’ stock and a ‘southern’ stock in the Sydney – Jervis Bay area. However, the current SESSF management and stock assessment assume a single stock because the evidence for the two-stock hypothesis was not conclusive (Morison et al. 2013).

Catch history

Catch of eastern school whiting increased markedly from around 500 t in the mid 1970s to a peak of around 2,500 t in the early 1990s. Historically, most of the total catch of eastern school whiting has come from New South Wales state waters. In recent years, the catch in these waters has decreased from historical levels of approximately 1,000 t per year to around 400 t.

Since 2014, the Commonwealth catch has made up approximately 50% of the total catch (Day 2017a), with Commonwealth-landed catch in the 2018–19 fishing season being 537 t (Figure 9.14). State catch was 707 t, and weighted average discards between 2014 and 2017 were 103.9 t (Castillo-Jordán et al. 2018).

FIGURE 9.14 Eastern school whiting annual catches (CTS, SHS and state combined) and fishing season TACs, 1947–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 do not include state catches and discards.
Sources: Day 2017a; AFMA catch disposal records (2017–2018)

Stock assessment

Eastern school whiting is managed as a tier 1 stock under the SESSF HSF (AFMA 2017a). The tier 1 assessment by Day (2017a) underpinned the management of the stock for the 2018–19 season.

The assessment estimated spawning biomass depletion in 2018 to be 47% of unfished levels (0.47SB0), which was marginally below the target reference point of 48% (0.48SB0) (Figure 9.15). An average RBC, over a three-year period (2018–2020), of 1,615 t was also calculated (Day 2017a). AFMA used this information to generate a three-year MYTAC (starting in the 2018–19 season) for Commonwealth fishers of 820 t (AFMA 2018b).

FIGURE 9.15 Spawning stock biomass for eastern school whiting, 1945–2016

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Day 2017a

Stock status determination

The most recent integrated assessment (Day 2017a) forecasted spawning stock biomass to be 47% of the unfished level at the beginning of 2018. Although slightly below the target reference point (0.48SB0), spawning stock biomass is estimated to be above the limit reference point. As a result, school whiting is classified as not overfished.

For the 2018–19 fishing season, the total landed catch was 537 t, the state catch was 706.97 t and the weighted average discards were 103.92 t (Castillo-Jordán et al. 2018). The landed catch and discards combined were 1,348 t, which is below the 2017 estimated RBC of 1,615 t. This indicates that the fishing mortality in 2018–19, if maintained, would be unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Flathead (Neoplatycephalus richardsoni and four other species)

Flathead (Neoplatycephalus richardsoni and four other species)

Line drawing: Rosalind Poole

Stock structure

For SESSF management purposes, ‘flathead’ refers to a group of species. However, the catch is almost entirely tiger flathead (Neoplatycephalus richardsoni). The ‘flathead’ group includes sand flathead (Platycephalus bassensis) and, from 1996 onwards, southern or ‘yank’ flathead (P.speculator), bluespot flathead (P.caeruleopunctatus), and gold-spot or toothy flathead (N.aurimaculatus).

Tiger flathead is endemic to Australia. It is found on sandy or muddy substrates in continental-shelf and upper-slope waters from Coffs Harbour in northern New South Wales through Bass Strait and around Tasmania to south-east South Australia (Kailola, FRDC & BRS 1993). Most of the Australian commercial catch comes from depths between 50 and 200 m. The stock structure of tiger flathead is poorly understood. There is some evidence of morphological variation across the distribution range, with observed regional differences in growth, appearance and the timing of reproduction, especially off eastern Tasmania. No stock identification studies using genetic or other techniques have been undertaken. For assessment and management purposes, a single stock has been assumed throughout all zones of the SESSF.

Catch history

Flathead catch has been historically variable, generally fluctuating between 1,500 and 4,000 t per year (Figure 19.6). The Commonwealth-landed catch of flathead in the 2018–19 fishing season was 2,036 t, taken almost entirely from the CTS (Table 9.2). State catches were 196.2 t, and weighted average discards between 2014 and 2017 were 124.7 t (Castillo-Jordán et al. 2018).

FIGURE 9.16 Flathead annual catches (CTS and state combined) and fishing season TACs, 1915–2018

Notes: TAC Total allowable catch. Data for 2016–2018 do not include discards and state catch.
Sources: Day 2016, 2017b; AFMA catch disposal records (2016–2018 data)

Stock assessment

Flathead is managed as a tier 1 stock under the SESSF HSF (AFMA 2017a). The tier 1 assessments by Day (2016, 2017b) underpinned the management of flathead for the 2018–19 season. The flathead assessment is based on biological parameters for tiger flathead, which accounts for about 95% of the flathead catch (Morison et al. 2013).

The updated 2017 assessment predicted spawning biomass depletion for 2018 of 41.6% (0.42SB0), which is above the target reference point of 40% (0.40B0) (AFMA 2017b), and produced an RBC of 2,865 t (Day 2017b) (Figure 9.17).

The 2,507 t TAC for the 2018–19 season is the second year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.17 Estimated spawning stock biomass for flathead, 1913–2015

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Sources: Day 2016, 2017b

Stock status determination

The most recent assessment predicts the spawning biomass of the flathead stock to be above the target reference point. As a result, the stock is classified as not overfished.

For the 2018–19 fishing season, the landed catch and discards combined were 2,357 t, which is below the RBC of 2,837 t. This indicates that the fishing mortality in 2018–19, if maintained, would be unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Gemfish, eastern zone (Rexea solandri)

Gemfish, eastern zone (Rexea solandri)

Line drawing: Sharne Weidland

Stock structure

There are two biologically distinct stocks of gemfish in Australia: an eastern stock and a western stock, separated by a boundary on the western side of Bass Strait (Colgan & Paxton 1997; Moore, Ovenden & Bustamante 2017).

Catch history

Catch of gemfish (eastern zone) peaked in 1978 at more than 6,000 t. Catch decreased rapidly after 1987, to between 50 and 100 t between 2000 and 2012. Since 2013, catch has been below 50 t (Figure 9.18).

Total fishing mortality (including Commonwealth and state catches and discards over the past five years) has been variable since 2013. In 2013, discards alone were around 141 t—around double the landed catch at the time (Castillo-Jordán et al. 2018). Since 2014, total mortalities have been below the incidental catch allowance of 100 t—that is, 72.7 t in 2014 (discards 35.3 t; catches 37.4 t), 67.6 t in 2015 (discards 38.1 t; catches 29.5 t), 40.7 t in 2016 (discards 10.4 t; catches 30.3 t) and 68.6 t in 2017 (discards 36.5 t; catches 32.1 t) (Castillo-Jordán et al. 2018). Total state catches from 2014 to 2017 did not exceed 11 t (Castillo-Jordán et al. 2018).

For the 2018–19 fishing season, trawl (33.9 t) and non-trawl (5.1 t) landings (39.1 t in total) were slightly higher than the landings in the previous two seasons (30.4 t in 2016–17 and 32.2 t in 2017–18). State catch was 4.4 t, and weighted average discards between 2014 and 2017 were 29.7 t (Castillo-Jordán et al. 2018). Total catch, including discards for the 2018–19 fishing season, was 73.2 t.

FIGURE 9.18 Gemfish annual catches (CTS, SHS and state combined) and fishing season TACs, eastern zone, 1968–2018

Notes: TAC Total allowable catch. Data for 2015–2018 do not include discards and state catch.
Sources: Little & Rowling 2011; AFMA catch disposal records (2009–2018 data)

Stock assessment

Eastern gemfish is currently managed under a rebuilding strategy (AFMA 2015a) that states that the stock should be rebuilt to, or above, the limit reference point by 2027 (19 years from 2008). Projections to support this time frame rely on at least average levels of recruitment and assume that total removals are limited to the 100 t incidental catch allowance.

The most recent assessment was completed in 2010 using data on catch and length frequency up to 2009 (Little & Rowling 2011). The base-case model estimated that the spawning stock biomass in 2009 was 15.6% of the 1968 level (0.156SB0) (Figure 9.19). A preliminary update of the 2010 assessment in 2016 (Little 2016) indicated that the spawning stock biomass in 2015 had decreased to 8.3% (0.083SB0), likely as a result of a lack of recruitment to the fishery (AFMA 2016c).

The 2010 assessment (Little & Rowling 2011) included projections of eastern gemfish biomass that were based on two scenarios: total catches of 100 t each year and zero catches each year. The projection for zero catch indicated that biomass may reach the limit reference point of 0.2SB0 by 2017. Projections for annual catches of 100 t saw biomass reach the limit reference point in 2025 (Little & Rowling 2011).

In 2011, an analysis of spawning potential ratio (SPR) based on the 2010 assessment (Little 2012) provided a measure of annual fishing mortality, expressed as the ratio of the spawning ability of the current stock to that of the unfished (‘equilibrium’) stock. The SPR analyses suggest high fishing mortality rates for eastern gemfish until the late 1990s, but much lower rates since 2002. The direct proxy for fishing intensity is determined by subtracting the SPR value from 1 (that is, 1 – SPR). The fishing intensity was above 0.5 in the late 1970s to 2000 but has declined to below 0.3 since 2002 (Little 2012).

Stronger year-classes moving through the fishery and high discard rates may be a sign of increased recruitment and stock rebuilding; however, age-frequency data for 2014 show a strong truncation, with few mature fish (Thomson et al. 2015). The reasons for this are unclear; contributing factors may include industry efforts to avoid the species, unfavourable environmental conditions, or distribution of the fish in the population.

Moore, Ovenden & Bustamante (2017) estimated the effective population sizes for both the eastern and western stocks of gemfish using microsatellite markers. The results suggest that genetic drift is occurring in the eastern stock but not in the western stock. This suggests that the spawning biomass in the eastern stock has fewer effective genetically successful contributors between generations than expected. Hybridisation between the eastern and western populations was detected; however, there was no evidence of introgression of genetic material between the populations, suggesting that all hybrids are sterile. It is unclear at this stage what is contributing to the decreased effective population size in eastern gemfish.

FIGURE 9.19 Estimated spawning stock biomass of gemfish, eastern zone, 1965–2008

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Little & Rowling 2011

Stock status determination

The most recent (2010) estimate of spawning stock biomass was 15.6% of the 1968 level in 2008, which is below the limit reference point (0.2SB0). Subsequent, but preliminary, analyses indicate that biomass may have decreased further to 8.3% in 2015. As a result, eastern gemfish remains classified as overfished.

Total catch, including discards, for the 2018–19 fishing season was around 74 t, which is below the incidental catch allowance of 100 t. However, there is little evidence that the stock is recovering, and indications that it may have actually declined further since the last accepted assessment. Additionally, the level of fishing mortality that will allow the stock to rebuild if recruitment conditions are below average is unknown. On this basis, the fishing mortality of the stock is classified as uncertain.

Gemfish, western zone (Rexea solandri)

Stock structure

The eastern and western gemfish stocks in Australia are separated by a boundary on the western side of Bass Strait (Colgan & Paxton 1997; Moore, Ovenden & Bustamante 2017). Genetic studies indicate that gemfish throughout the western zone, including in the CTS and in the GABTS, is one biological stock (Moore, Ovenden & Bustamante 2017).

Catch history

Western gemfish is fished in both the GABTS and the CTS; however, the TAC applies only to the CTS (AFMA 2018b). Western gemfish is targeted in the CTS, whereas incidental catches are more common in the GABTS. Western gemfish was targeted in the GABTS over four years from 2004 to 2007, and catches were as high as 532 t (Figure 9.20). In 2008, targeted fishing for western gemfish in the GABTS ceased and catches became largely incidental, partly due to low prices for gemfish and a key vessel leaving the fishery (AFMA 2010). Commonwealth-landed catch in the 2018–19 fishing season was 78.5 t. Weighted average discards between 2014 and 2017 were 77.4 t, and there were no state catches (Castillo-Jordán et al. 2018).

FIGURE 9.20 Gemfish annual catches (CTS and SHS) and fishing season TACs, western zone, 1985–2018

Notes: TAC Total allowable catch. Data for 2016–2018 exclude discards and state catches.
Sources: Helidoniotis & Moore 2016; AFMA catch disposal records (2016–2018 catch data)

Stock assessment

Management arrangements for western gemfish currently differ between the CTS and the GABTS. Western gemfish catch in the CTS is currently managed under a three-year MYTAC. The GABTS has not moved to implement quota for western gemfish, instead relying on a catch trigger, which would manage the stock as a tier 1 stock under the SESSF HSF (AFMA 2017a) if catch exceeds 1,000 t over three years (AFMA 2018b). Western gemfish is managed as a tier 4 stock under the SESSF HSF (AFMA 2017a) when catches are less than 1,000 t over three years.

Historically, the management of the stock alternated between a tier 4 analysis and a tier 1 assessment. The tier 1 assessment by Helidoniotis and Moore (2016) underpinned the management of western gemfish in zones 40 and 50 of the CTS for the 2018–19 season. The assessment predicted that spawning biomass depletion in 2019 would be 54% (0.54SB0), which is above target reference point (0.48SB0) (Figure 9.21). An RBC of 200.4 t was generated for the CTS. Catches in the GABTS are not considered.

AFMA implemented a TAC of 200 t for the 2018–19 fishing year, the second year of a three-year MYTAC (AFMA 2018b). A tier 4 analysis was recently conducted (Haddon & Sporcic 2017b), and the recent four-year average CPUE (2013–2016) was above the target, which was consistent with the tier 1 assessment.

FIGURE 9.21 Estimated spawning stock biomass of gemfish, western zone, 1985–2018, for the CTS and the GABTS

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Helidoniotis & Moore 2016. Data for 2015–2018 are predicted values.

Stock status determination

Estimated spawning biomass in 2019 is above the target reference point. The stock is therefore classified as not overfished.

Total catch for the stock in the 2018–19 season was 156 t, which is below the 200 t RBC and TAC. This indicates that, if catches in 2018–19 were maintained, they would be unlikely to deplete the stock below the limit reference point. The stock is therefore classified as not subject to overfishing.

Gulper sharks (Centrophorus harrissoni, C. moluccensis, C. zeehaani)

Gulper sharks (Centrophorus harrissoni, C. moluccensis, C. zeehaani)

Line drawing: FAO

Stock structure

Gulper sharks are assessed as a multispecies stock comprising Harrisson’s dogfish (Centrophorus harrissoni), southern dogfish (C.zeehaani) and endeavour dogfish (C.moluccensis). Harrisson’s dogfish is endemic to south-eastern Australia, from southern Queensland to south-eastern Tasmania, and adjacent seamounts. Southern dogfish is endemic to southern Australia, from Shark Bay in Western Australia to Forster in New South Wales (Williams et al. 2013). Endeavour dogfish has a broader range than Harrisson’s and southern dogfish, extending beyond the boundaries of the SESSF and Australia. Within Australia, endeavour dogfish occurs along the west and east coasts, but is uncommon off the south coast (Last & Stevens 2009). Greeneye spurdog (Squalus chloroculus) is widely distributed in temperate and subtropical waters of most oceans, and may constitute a species complex (Last & Stevens 2009).

To support the revision of the AFMA Upper-slope dogfish management strategy (AFMA 2012) in 2013, Williams et al. (2013) investigated the relative carrying capacity and depletion of subpopulations of Harrisson’s and southern dogfish. Results indicated different depletion levels in different areas, suggesting the separation of gulper sharks into several populations: a continental margin and a seamount population for Harrisson’s dogfish; and eastern, central and western populations for southern dogfish.

Catch history

Estimated landings of gulper sharks (derived from liver oil production from 1994 to 2001) averaged about 20 t (trunk weight) from 1994 to 1998, with a peak of 40 t in 1995. Catches averaged about 10 t from 2002 to 2005 and have since declined. Despite gulper sharks being a no-take multispecies stock, landings for the trawl fishery have been recorded in recent years (Figure 9.22). This may reflect reporting errors. There is also the potential for unreported or underestimated discards, based on the large degree of overlap of current fishing effort with the core range of the species. Low levels of mortality can pose a risk for such depleted populations. The reported catch in the 2017–18 and 2018–19 fishing seasons was 0.35 t and 0.38 t, respectively.

FIGURE 9.22 Gulper shark annual catch and discards for the SESSF (all sectors), 1994–2018

Notes: Estimated catch of upper-slope gulper sharks from 1994 to 2001 is based on liver oil quantity. Catch history is compiled using data from various sources.

Stock assessment

Gulper sharks have very low productivity due to a slow growth rate, late age at maturity and low fecundity. These life-history characteristics place them at relatively higher risk of depletion from low levels of fishing effort, and also make their recovery slow once stocks are depleted (Daley, Stevens & Graham 2002; Simpfendorfer & Kyne 2009; Williams et al. 2013). Williams et al. (2013) have shown that gulper sharks undertake day–night migrations across their depth range, from relatively deep daytime residence depths (to 1,000 m) to shallower night-time feeding depths (up to 200 m), rendering them susceptible to capture over a wide depth range. Williams et al. (2013) also found that the geographic distribution of fishing during periods of high fishing effort in the CTS (1984–2011), demersal and auto-longline fisheries (1992–2010), Commonwealth gillnet fisheries (1997–2010) and New South Wales state fisheries coincides with the most depleted areas of Harrisson’s and southern dogfish. Post-capture survival of gulper sharks in the trawl sector is low; most gulper sharks are dead when the net is hauled. In the auto-longline sector, post-capture survival is potentially higher (subject to fishing gear soak time and handling practices); a preliminary study by CSIRO estimated post-capture survival at 60–93% for the 70 southern dogfish tagged and released in the study (Williams et al. 2013).

Gulper sharks were historically targeted because they have high squalene (liver oil) content. The resulting historical depletion of gulper sharks off the east coast is well documented (Graham, Andrew & Hodgson 2001; Wilson et al. 2009). Graham, Andrew & Hodgson (2001) reported declines in CPUE of 95.8–99.9% between research trawl surveys conducted in 1976–77 and 1996–97 for greeneye spurdog, and endeavour, Harrisson’s and southern dogfish on the New South Wales upper slope. Williams et al. (2013) derived depletion estimates for the identified subpopulations of Harrisson’s and southern dogfish, expressed as a percentage of the initial relative carrying capacity. For Harrisson’s dogfish, the continental margin population was estimated to be at 11% of carrying capacity (range 4–20%) and the seamount population at 75% (range 50–100%). For southern dogfish, the eastern population was estimated to be at 11% of carrying capacity (range 6–19%) and the central population at 16% (range 8–33%). No estimate could be derived for the western population of southern dogfish because of limited data availability. Williams et al. (2013) confirmed that, in some areas, large reductions in abundance had resulted from quite low levels of fishing effort.

AFMA released the Draft upper slope dogfish management strategy in 2009, which protected several areas of known occurrence of dogfish, and implemented daily catch and trip limits (AFMA 2009). The strategy was reviewed by Musick (2011) and found to be inadequate to ensure recovery of Harrisson’s, southern and endeavour dogfish, and greeneye spurdog, with fishing mortality still exceeding estimated sustainable levels. The strategy was subsequently revised in 2012, following research on depletion rates of upper-slope dogfish subpopulations (Williams et al. 2013), with a recovery objective of rebuilding Harrisson’s and southern dogfish stocks to 25% of their original carrying capacity. Williams et al. (2013) examined the amount of core habitat area for Harrisson’s and southern dogfish that would be protected under a proposed closure network designed to meet this objective. Under the closure network, it is estimated that, in AFMA-managed waters, 25% of the core habitat of Harrisson’s dogfish on the continental shelf and slope, 16.2% of the core habitat of the eastern population of southern dogfish and 24.3% of the core habitat of the central population of southern dogfish would be protected (from trawling and/or demersal longline fishing). These closures were implemented in February 2013. Additional closures were subsequently implemented on the Tasmanian seamounts (Britannia, Derwent Hunter and Queensland) overlaying the Murray and Freycinet Commonwealth marine reserves (areas that allow access to line fishing) (AFMA 2014c).

On 30 May 2013, the then Minister for Sustainability, Environment, Water, Population and Communities listed Harrisson’s dogfish and southern dogfish under the EPBC Act as threatened species in the conservation-dependent category. The minister noted that both species have experienced severe historical declines following overfishing, and are subject to recovery plans that provide for management actions to stop their decline and support their recovery. Measures to further reduce fishing mortality include a combined trigger limit of three Harrisson’s dogfish and/or southern dogfish; a zero retention limit for greeneye spurdog, and Harrisson’s, southern and endeavour dogfish; and guidelines for handling practices. In 2014, a research and monitoring workplan was developed to establish methods for monitoring the rebuilding of dogfish abundance.

Stock status determination

In the absence of any evidence of recovery to above the limit reference level, gulper sharks remain classified as overfished because of the substantial depletion of Harrisson’s and southern dogfish in areas of southern and eastern Australia.

Although it has been estimated that the closures implemented in 2013 will protect 16.2–25% of the core distribution areas of these species, no evidence has yet been obtained showing rebuilding, and the effect of the closures remains to be seen. As a result, the level of fishing mortality of gulper sharks is classified as uncertain. Resolution of stock structure may result in one or more of the subpopulations being classified as not subject to overfishing.

Jackass morwong (Nemadactylus macropterus)

Jackass morwong (Nemadactylus macropterus)

Line drawing: FAO

Stock structure

Jackass morwong is distributed around the southern half of Australia (including Tasmania), New Zealand, and St Paul and Amsterdam islands (Indian Ocean); and off south-eastern South America and southern Africa. It occurs to depths of 450 m and, in Australian waters, is most abundant between 100 and 200 m. Genetic studies have shown no evidence of separate stocks in Australian waters, but found that New Zealand and Australian stocks are distinct (Elliott & Ward 1994). Although analysis of otolith microstructure found differences between jackass morwong from southern Tasmania and those off New South Wales and Victoria, it is unclear whether such differences indicate separate stocks (Morison et al. 2013). Nonetheless, it is assumed for the purposes of the stock assessment that there are separate stocks of jackass morwong in the eastern (New South Wales and eastern Victoria) and western (western Tasmania and western Victoria) zones (Morison et al. 2013). Catches of jackass morwong are also reported from the GABTS (Chapter 11), but this stock is currently managed separately from the western stock.

Catch history

Catches of jackass morwong peaked at more than 2,500 t in the mid 1960s and have declined since the 1980s. During the past five years, catches have continued to decline and have been less than 500 t per year (Figure 9.23). For the eastern stock, the catch (logbook data) was 124 t in the 2018–2019 season, the average state catch was 6.4 t, and weighted average discards between 2014 and 2017 were 14 t, giving a total of 144.4 t (Castillo-Jordán et al. 2018). For the western stock, the catch (logbook data) was 35.9 t in the 2018–2019 season, the average state catch was 1.3 t, and weighted average discards between 2014 and 2017 were 3.9 t, giving a total of 41.1 t (Castillo-Jordán et al. 2018). Commonwealth-landed catch in the 2018–19 fishing season was 186 t. State catch was 7.8 t, and weighted average discards between 2014 and 2017 were 17.9 t (Castillo-Jordán et al. 2018), giving a total of 211.7 t.

FIGURE 9.23 Jackass morwong annual catches (CTS, SHS and state combined) and fishing season TACs, eastern and western stocks combined, 1915–2018

Notes: TAC Total allowable catch. Data for 2018 do not include discards and state catches.
Sources: Tuck, Day & Castillo-Jordán 2018a,b; AFMA catch disposal records (2018 catch data)

Stock assessment

Jackass morwong is managed as a tier 1 stock under the SESSF harvest strategy (AFMA 2017a). Separate integrated stock assessment models have been developed for the eastern (southern New South Wales to eastern Tasmania) and western (western Tasmania to western Victoria) stocks. Assessments for the eastern and western stocks were published in 2011 (Wayte 2012), 2013 (Wayte 2014), 2015 (Tuck et al. 2015a, b; Tuck, Day & Wayte 2015) and 2018 (Tuck, Day & Castillo-Jordán 2018a, b).

The major changes between the 2015 and 2018 assessments for both stocks were the addition of estimated discard rates, new tuning methods (Francis weighting) and recruitment estimated for an additional year (AFMA 2018c).

For the eastern stock, a new base-case assessment in 2011 involved a change in productivity (a ‘regime shift’), attributed to long-term oceanographic changes (Wayte 2013). The new base case provided a better fit to the data, but the assessment remained sensitive to natural mortality, the last year of recruitment estimation and the stock–recruitment relationship (Tuck, Day & Wayte 2015). The adoption of a ‘regime shift scenario’ in the stock assessment resulted in a more optimistic spawning biomass depletion from 0.26B0 in 2011 to 0.35B0 (that is, 35% of the 1988 equilibrium biomass) in 2019, which is between the limit reference point (0.2B0) and the target reference point (0.48B0) (Figure 9.24). The analyses of Wayte (2013), which provided evidence for a regime shift, have now been accepted as influencing jackass morwong productivity (AFMA 2018c). However, SERAG has acknowledged that the regime shift contributes to considerable uncertainty in the jackass morwong assessment and that in the future there is a need to consider how best to fit regime/productivity shifts into models for non-recovering species (AFMA 2018c, d).

For the western stock, assessments are uncertain because only sporadic age data are available, length compositions are based on a very low number of sampled fish and the quality of the CPUE data is questionable (AFMA 2015c, 2018c). The 2018 assessment predicted the spawning stock biomass to be 0.68B0 in 2019 (compared with 0.69B0 in 2015), which is above the target reference point of 0.48B0 (Figure 9.24).

FIGURE 9.24 Estimated spawning stock biomass for eastern (1988–2017) and western (1984–2017) stocks of jackass morwong

Notes: BCURRENT Current biomass. BREF Unfished biomass. Biomass estimates are available for the eastern stock from 1915 to 1987. However, pre-1988 estimates are not presented for the eastern stock because the new regime shift base case resets the reference biomass to the biomass in 1988.
Source: Tuck, Day & Castillo-Jordán 2018a,b

Stock status determination

The western jackass morwong assessment (Tuck et al. 2015a, b) estimates that spawning biomass depletion in 2016 was 68% (0.68SB0), which is above the target reference point of 0.48SB0. Based on logbook data, catch of the western stock (61.4 t in 2018–19) is below the RBC estimated by the 2015 assessment. This indicates that the fishing mortality rate in 2018–19, if maintained, would be unlikely to deplete the stock to a level below its biomass limit reference point. The western stock is classified as not overfished and not subject to overfishing.

The acceptance of a recruitment shift in the assessment for eastern jackass morwong resulted in a decrease in the estimate of recent depletion from close to the limit reference point to closer to the target reference point. The eastern jackass morwong assessment (Tuck, Day & Wayte 2015) estimates that spawning biomass depletion in 2016 was 37% (0.37SB0), which is between the target and limit reference points. Based on logbook data, catch of the eastern stock (124.6 t in 2018–19) is below the RBC estimated by the 2015 assessment. This indicates that the fishing mortality rate in 2018–19, if maintained, would be unlikely to deplete the stock to a level below its biomass limit reference point. The eastern stock is classified as not overfished and not subject to overfishing.

For the 2018–19 fishing season, the total landed catch was 186.2 t, the average state catch was 7.8 t, and the weighted average discards were 17.9 t. The landed catch and discards combined were 211.8 t, which is below the RBC of 543 t estimated from the 2015 assessment for the 2018–19 fishing season. Based on the best available information, jackass morwong is classified as not overfished and not subject to overfishing.

Climate changes are considered to have resulted in a decrease in stock biomass for eastern jackass morwong. Although the regime shift scenario fitted the data better than a no-change scenario in productivity, other hypotheses to explain conflicts within the input data have not yet been fully explored. Establishing a mechanism for accepting regime shift scenarios is a SERAG priority for non-recovering species more broadly (AFMA 2018c). However, there is a knowledge gap about status determination in the presence of climate change.

John dory (Zeus faber)

John dory (Zeus faber)

Line drawing: Rosalind Poole

Stock structure

John dory inhabits coastal and continental-shelf waters of Australia, the western Indian Ocean, the eastern Atlantic Ocean, the Mediterranean Sea, Japan and New Zealand. In southern Australia, its distribution stretches from Moreton Bay in southern Queensland to Cape Cuvier in Western Australia, with a limited distribution in eastern Bass Strait. In recent years, most of the SESSF john dory catch has been taken off New South Wales and eastern Victoria (Morison et al. 2013). John dory in the SESSF is considered to constitute a single stock for assessment and management purposes.

Catch history

The catch of john dory averaged between 200 and 300 t from 1986 to 1995, peaking at about 400 t in 1993. Catches have since decreased and have been below 200 t per year since 2001 (Figure 9.25). Commonwealth-landed catch in the 2018–19 fishing season was 61.8 t. State catches were 7.27 t, and weighted average discards were 2.47 t (Castillo-Jordán et al. 2018).

John dory is infrequently targeted in the SESSF. Most of the catch was historically taken as byproduct by trawlers targeting other shelf species, such as redfish and flathead. Because most john dory catches are not targeted, it is considered a ‘secondary species’ rather than a target species, and is managed to the default biomass at maximum sustainable yield (BMSY) proxy target of 0.4B0.

FIGURE 9.25 John dory annual catches (CTS, SHS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2014–2018 do not include discards and state catch.
Sources: Haddon 2014; AFMA catch disposal records (2014–2018 catch data)

Stock assessment

John dory was managed as a tier 3 stock under the SESSF HSF (AFMA 2017a). The tier 3 assessment by CSIRO in 2017 (Castillo-Jordán 2017) underpinned the management of john dory for the 2018–19 season. The assessment accounted for catches in zones 10–80 of the SESSF (Castillo-Jordán 2017), which comprise the GABTS, the CTS and the East Coast Deepwater Trawl Sector. The analysis consisted of a yield-per-recruit model and catch-curve analysis, and was an update to the yield analyses presented in Thomson (2014).

Total mortality was estimated from catch curves constructed from length-frequency information. The assessment estimated an equilibrium fishing mortality rate (FCURR) of 0.036, which was below the target fishing mortality reference point (Fspr40 = 0.126) that would achieve a biomass of 0.4B0. This indicates that the current biomass is likely to be above this target. There is no historical evidence to suggest that the stock has previously fallen below the target. Application of the tier 3 harvest control rule to the outputs of the 2017 assessment, and using the 0.4B0 target, generated an RBC of 485 t for the 2018–19 season (AFMA 2018b; Castillo-Jordán 2017). This is higher than the RBC estimated by the 2014 assessment, largely as a result of the new ageing data. The lower RBC in the previous assessment was due to the stock being estimated to be more depleted (Castillo-Jordán 2017; Tuck 2014). This variability in biomass depletion demonstrates that the tier 3 produced variable results. In another report on standardised CPUE, the results indicated that the john dory stock in zones 10–20 has stabilised (Sporcic & Haddon 2018a). The 2018–19 TAC was 263 t, the first year of a three-year MYTAC (AFMA 2018b).

Stock status determination

The latest estimate of fishing mortality was below the target, indicating that fishing mortality is at a level that is unlikely to reduce the stock to below the biomass limit reference point. In addition, recent catches are low relative to historical levels. For the 2018–19 fishing season, the total landed catch was 61.8 t, weighted average discards were 2.5 t and state catches were 7.3 t, giving a total of 71.5 t. This is below the RBC of 485 t. As a result, the stock is classified as not subject to overfishing and not overfished.

Mirror dory (Zenopsis nebulosa)

Mirror dory (Zenopsis nebulosa)

Line drawing: FAO

Stock structure

Mirror dory is found throughout the southern Pacific Ocean at depths of 30–800 m. A single stock of mirror dory in the SESSF area is assumed for management purposes (Morison et al. 2013). To make it easier to assess, the stock has been split into eastern and western management units.

Catch history

Most of the mirror dory catch is byproduct in the CTS, mainly caught east of Bass Strait. The catch has ranged between 200 and 700 t per year (Figure 9.26). Commonwealth-landed catch in the 2018–19 fishing season was 118 t. Weighted average discards between 2014 and 2017 were 7.01 t in the east and 0.32 t in the west, and state catch was 4.93 t in the east (no reports for the west) (Castillo-Jordán et al. 2018).

FIGURE 9.26 Mirror dory annual catches (CTS, SHS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2018 do not include discards and state catch.
Sources: Sporcic 2018; AFMA catch disposal records (2018 catch data)

Stock assessment

Mirror dory was managed as a tier 4 stock under the SESSF HSF (AFMA 2017a).

The analyses that underpinned the management of mirror dory for the 2018–19 season were the standardisation of catch rates and application of the tier 4 harvest control rules, as reported by Haddon and Sporcic (2017b). The assessments included discards for the eastern stock but not for the western stock, given the lower level of discards (AFMA 2018a).

The stock was subdivided into an eastern unit (zones 10–30) and a western unit (zones 40–50) for analysis. For the eastern unit, applying the tier 4 harvest control rule to the standardised CPUE series with discards resulted in an RBC of 198 t (Haddon & Sporcic 2017b). For the western unit, applying the tier 4 harvest control rule to the standardised CPUE series resulted in an RBC of 122 t (Haddon & Sporcic 2017b).

The total RBC for the eastern and western units combined for the 2018–19 season was 322 t (AFMA 2018e). Recent average CPUE was above the limit reference point but below the target reference point for both the western (Figure 9.27) and eastern (Figure 9.28) units.

Consistent with SERAG advice, the AFMA Commission set the TAC for mirror dory at 253 t for the 2018–19 fishing year (AFMA 2018e).

FIGURE 9.27 Standardised CPUE for western mirror dory, 1986–2017

Note: CPUE Catch-per-unit-effort.
Source: Sporcic 2018

FIGURE 9.28 Standardised CPUE for eastern mirror dory, 1986–2017

Note: CPUE Catch-per-unit-effort.
Source: Sporcic 2018

Stock status determination

Recent average CPUE for the eastern and western units are above their respective limit reference points. As a result, the stock is classified as not overfished.

For the 2018–19 fishing season, the RBC for the eastern and western units combined was 322 t (AFMA 2018b). Total landed catch was 118 t, the total weighted average discards between 2014 and 2017 for the east and west combined were 7.3 t, and the total average state catch was 4.93 t (Castillo-Jordán et al. 2018). The landed catch and discards combined were 130 t, which is below the RBC of 322 t. This indicates that the fishing mortality in 2018–19, if maintained, would be unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Ocean jacket (predominantly Nelusetta ayraud)

Ocean jacket (predominantly Nelusetta ayraud)

Line drawing: FAO

Stock structure

The ocean jacket stock comprises chinaman leatherjacket, which makes up most of the catch, and unspecified leatherjackets. Little is known about the biological structure of this multispecies stock. Ocean jacket taken in the GABTS is assessed separately (Chapter 11). Ocean jacket is a relatively short-lived species (six years), reaching maturity within 2–3 years and exhibiting large cyclical changes in abundance (Miller & Stewart 2009).

Catch history

Ocean jacket is caught in the CTS (zones 10–50), and in zones 82 and 83 in the Great Australian Bight. Only trawl-caught catches from the CTS are considered here. Historical catch data indicate substantial variations in ocean jacket abundance off south-eastern Australia in the 1920s and 1950s (Miller & Stewart 2009). Total catch of ocean jacket remained stable, at around 50 t, between 1986 and 2001 (Figure 9.29). Since then, ocean jacket has been an important non-quota byproduct species in the SESSF, with current catch levels exceeding those of many quota species. Catch peaked in 2016 at 475 t. Commonwealth-landed catch in the 2018–19 fishing season was 129 t. Weighted average discards between 2014 and 2017 were 395.5 t, and average state catch was 367.4 t (Castillo-Jordán et al. 2018). The landed catch and discards combined in 2018–19 were 891 t.

FIGURE 9.29 Ocean jacket catch in the CTS and the SHS, 1986–2018

Note: Catch includes chinaman leatherjacket and unspecified leatherjackets. Data from 2017 and 2018 do not include discards or state catches.
Sources: Haddon & Sporcic 2017a; AFMA catch disposal records (2017–2018 catch data)

Stock assessment

There is no formal stock assessment for ocean jacket. A standardised CPUE series shows a similar trend to landings, suggesting that abundance of ocean jacket increased after 2003. Following a gradual decline since 2013 the CPUE increased in 2017 (Sporcic & Haddon 2018a). There continues to be uncertainty over discarding of this species in the CTS and the GHTS.

FIGURE 9.30 Standardised CPUE for ocean jacket, 1986–2014

Note: CPUE Catch-per-unit-effort. There is no tier 4 assessment for ocean jacket, and so there are no target and limit reference points.
Source: Haddon & Sporcic 2017a

Stock status determination

The standardised CPUE series increased substantially between 2003 and 2007, and remains relatively high (Sporcic & Haddon 2018a). Ocean jacket is therefore classified as not overfished.The landed catch and discards combined in 2018–19 were 891 t, which is an increase on previous years; however,CPUE remains relatively high compared with historical levels. As a result, ocean jacket is classified as not subject to overfishing.

Ocean perch (Helicolenus barathri, H. percoides)

Ocean perch (Helicolenus barathri, H. percoides)

Line drawing: FAO

Stock structure

Ocean perch is managed as a single stock that includes two species: the inshore reef ocean perch (Helicolenus percoides) and the offshore bigeye ocean perch (H.barathri). Ocean perch stock structure is uncertain, but there is probably an east–west structuring of stocks (Morison et al. 2013). Reef ocean perch and bigeye ocean perch have been assessed separately since 2009, but a single TAC is set for the two species. Based on the depth of capture and logbook records, most of the landed ocean perch is considered to be bigeye ocean perch.

Catch history

Bigeye ocean perch has been a significant part of trawl catches since the continental-slope trawl fishery developed in the late 1960s (Morison et al. 2013). Total landed catch (both species) of ocean perch since the 1970s has generally been between 200 and 400 t, peaking at 475 t in 1997. The Commonwealth-landed catch in the 2018–19 fishing season was 194 t (Figure 9.31).

Most (inshore) reef ocean perch are discarded because of their smaller size. About 85% of total mortalities (catch plus discards) were discards (Castillo-Jordán et al. 2018). Weighted average discards of (inshore) reef ocean perch between 2014 and 2017 were 54 t, and average state catches were 4.1 t (Castillo-Jordán et al. 2018). Discards for (offshore) bigeye ocean perch are lower; about 30% of total mortalities (catch plus discards) were discards (Castillo-Jordán et al. 2018). Weighted average discards of (offshore) bigeye ocean perch between 2014 and 2017 were 58.3 t, and average state catches were 15.12 t (Castillo-Jordán et al. 2018).

FIGURE 9.31 Total ocean perch (reef and bigeye) annual catches (CTS, SHS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 exclude discards and state catch.
Sources: Haddon & Sporcic 2017b; AFMA catch disposal records (2017–2018 catch data)

Stock assessment

Both stocks are managed as tier 4 stocks under the SESSF HSF (AFMA 2017a). A B40 (BMSY proxy) target reference point is applied to both species (Morison et al. 2013).

The standardised CPUE and associated tier 4 assessment by Haddon and Sporcic (2017b) underpinned the management of reef and bigeye ocean perch for the 2018–19 season.

The 2017 tier 4 analyses produced an RBC of 247 t for reef ocean perch and 345 t for bigeye ocean perch (Haddon & Sporcic 2017b). The RAG noted that the high discard rate for reef ocean perch had made the standardisation and associated tier 4 analyses uncertain, and, given the amount of discards required to be deducted, would have resulted in a TAC of zero (AFMA 2018e). The RAG recommended that reef ocean perch be removed from the ocean perch quota basket and that a catch trigger be set for the species instead (AFMA 2018b). Accordingly, the TAC was determined based on the RBC for offshore ocean perch only and was set at 241 t for 2018–19, the first year of a three-year MYTAC (AFMA 2018b).

The four-year average CPUE (2013–2016) for (offshore) bigeye ocean perch was between the target and limit reference points (Figure 9.32). The standardised CPUE for reef ocean perch is no longer accepted by the RAG and is no longer being used to recommend an RBC.

FIGURE 9.32 Standardised CPUE for bigeye (offshore) ocean perch, 1986–2016

Note: CPUE Catch-per-unit-effort.
Source: Haddon & Sporcic 2017b

Stock status determination

Since the standardised CPUE for reef ocean perch is no longer accepted by the RAG and is no longer being used to recommend an RBC, future status for the ocean perch stock will likely be based only on information for the offshore species. Noting uncertainties in the CPUE series for reef ocean perch, the recent average CPUE was above the limit for both species (Haddon & Sporcic 2017b). As a result, the stock is considered to be not overfished.

Noting uncertainties in the CPUE series for reef ocean perch and the resulting uncertainties in the RBC that was derived from the tier 4 harvest control rules, the total catch mortality for (inshore) reef ocean perch was 81.6 t, which is below the RBC of 247 t. The total catch (landed catch plus discards) for bigeye ocean perch was 182.8 t, which is below the RBC of 345 t. As a result, the fishing mortality status for the ocean perch stock is classified as not subject to overfishing.

Orange roughy (Hoplostethus atlanticus)

Orange roughy (Hoplostethus atlanticus)

Line drawing: Rosalind Poole

Stock structure

Orange roughy in the CTS is currently broken up into seven management zones: Cascade Plateau, eastern zone, southern zone, western zone, South Tasman Rise, north-east remote zone and southern remote zone (Figure 9.33). An orange roughy stock occurs in the Great Australian Bight, outside the CTS, but is not included in this chapter. A study on genetic variation in orange roughy (Gonçalves da Silva, Appleyard & Upston 2012) examined the variation of a large number of loci, using genetic techniques that have the power to detect low levels of genetic differentiation. The study concluded that orange roughy in the Australian Fishing Zone form a single genetic stock, but identified some differentiation between Albany/Esperance, Hamburger Hill (in the Great Australian Bight) and south-eastern Australia. It was noted that the amount of genetic exchange needed to maintain genetic homogeneity is much less than the amount needed for demographic homogeneity, and that residency or slow migration may result in separate demographic units despite genetic similarity (Morison et al. 2013). Orange roughy on the Cascade Plateau has distinct morphometrics, parasite populations, size and age composition, and spawning time, and is considered to be a separate management unit within the southern remote zone (AFMA 2014d).

FIGURE 9.33 Management zones for orange roughy in the SESSF

Overall catch history

Orange roughy was historically targeted in aggregations around seamounts, mainly at depths from 600 m to about 1,300 m. The first aggregation was discovered off Sandy Cape, western Tasmania, in 1986 (Smith & Wayte 2004). Several other non-spawning aggregations were discovered in 1986 and 1988, producing annual landings ranging from 4,600 to 6,000 t. The discovery of a large spawning aggregation on St Helens Hill and elsewhere off eastern Tasmania in 1989 resulted in significant growth of the fishery, with declared catches exceeding 26,000 t in 1989 and 40,000 t in 1990, making this the largest and most valuable finfish fishery in Australia at the time (Morison et al. 2013). Catches declined steadily after 1990, reaching low levels between 2000 and 2005. Following indications of decreasing CPUE and availability, the introduction of management zones and TACs prevented further increases in catches of orange roughy (Smith & Wayte 2004). Individual catch histories for the Cascade Plateau, eastern, southern and western orange roughy zones are shown in Figures 9.34, 9.35, 9.37 and 9.38.

In October 2006, orange roughy was listed as conservation-dependent under the EPBC Act and placed under the Orange Roughy Conservation Programme (ORCP). The ORCP was replaced by the Orange Roughy Rebuilding Strategy (ORRS) in 2015 (AFMA 2015b), the primary objective of which is to return all orange roughy stocks to levels at which the species can be harvested in an ecologically sustainable manner. Management actions to minimise fishing mortality and support rebuilding include deepwater closures, targeted fishing for orange roughy stocks that are above the limit reference point of 20% of the unfished spawning biomass, restricting effort by limiting entry to existing fisheries, and ongoing research and monitoring to support stock assessments.

Orange roughy, Cascade Plateau

Catch history

Orange roughy on the Cascade Plateau is the only orange roughy fishery assessed in the CTS that is not estimated to have been depleted to below the limit reference point; this fishery shows a somewhat different catch trend from the depleted fisheries. Catch of orange roughy on the Cascade Plateau peaked at 1,858 t in 1990. No catch was taken between 1991 and 1995. Catches have been below 10 t in recent years, despite the TAC remaining at 500 t, reflecting negligible effort in the fishery. The landed catch was 2 t in 2015–16; no catch was taken in 2016–17, 2017–18 or 2018–19 (Figure 9.34). Discard estimates and state catches were not reported in Castillo-Jordán et al. (2018) and are unknown.

FIGURE 9.34 Orange roughy catch (CTS), Cascade Plateau, 1989–2018

Notes: TAC Total allowable catch.
Sources: Various, including AFMA catch disposal records

Stock assessment

A requirement of the ORCP was to maintain the spawning biomass of orange roughy on the Cascade Plateau at or above 60% of the unfished biomass (0.6B0). After the ORRS was introduced, it adopted the standard target reference point of 0.48B0 and the limit reference point of 0.2B0, in line with the default settings of the SESSF HSF (AFMA 2017a). This revised target also applies to the Cascade Plateau stock.

Spawning aggregations of Cascade Plateau orange roughy have been assessed using acoustic survey abundance indices since 2003. These assessments rely on the single largest acoustic estimate of biomass each year, rather than trends in time series, because spawning aggregations on the Cascade Plateau are highly variable and have shown no discernible trends in volume or estimated biomass over time (Morison et al. 2013). Because fishing effort has been low, and therefore new data are lacking, the stock has not been formally assessed since 2009.

The 2006 assessment estimated female spawning biomass to be 0.73B0 (Wayte & Bax 2007). Because the stock was assessed to be above the 0.6B0 reference point that was in place at the time, application of the SESSF HSF tier 1 harvest control rules allowed the setting of TACs to enable fish-down towards the target reference point. Spawning aggregations did not form in 2007 and 2008, and the TAC was undercaught for the first time in the fishery’s history in 2007 (151 t caught out of a TAC of 500 t) and 2008 (121 t caught out of a TAC of 700 t).

Projections undertaken in 2009 using the 2006 stock assessment predicted that, if the 315 t long-term RBC was fully caught by 2011, the spawning biomass of the stock would be at 0.64SB0 in 2011 (Morison et al. 2012). Taking into account the lower catch levels of 2007 and 2008, the assessment suggested that a TAC of 500 t would maintain the stock at 0.63SB0 in 2011. Noting low fishing effort and a lack of new data, AFMA has continued to set an annual TAC of 500 t. This stock was scheduled for an assessment in 2014, but the assessment was postponed because no new catch or acoustic data were available.

Stock status determination

The projections undertaken in 2009 predicted that the 2011 spawning stock biomass of Cascade Plateau orange roughy would be at 63–64% of unfished levels (0.63–0.64SB0) if the long-term RBC of 315 t was fully caught by 2011. Recent catches have been less than 10 t (zero in 2016–17, 2017–18 and 2018–19). On the available evidence, the biomass is still likely to be significantly above the limit reference point. As such, the stock is classified as not overfished. Given the zero catch in 2018–19, the stock remains classified as not subject to overfishing.

Orange roughy, eastern zone

Catch history

The eastern, southern and western orange roughy fisheries show similar catch trends. The eastern zone has supported higher cumulative catches than the southern and western zones, producing a reported catch of 76,714 t from 1989 to 1992 (Figure 9.35).

Orange roughy catch in the eastern zone was limited to incidental catch allowances, to allow for unavoidable catches made while targeting other species. Most of the historical fishing grounds for orange roughy deeper than 700 m were also closed to trawling in January 2007 (AFMA 2006, 2015b). Targeted fishing for orange roughy in the eastern zone recommenced in the 2015–16 fishing season following acoustic surveys and an updated stock assessment. The Commonwealth-landed catch in the 2018–19 fishing season was 855.8 t (Figure 9.35). Weighted average discards between 2014 and 2017 were 2.74 t; there were no state catches (Castillo-Jordán et al. 2018).

FIGURE 9.35 Orange roughy catch (CTS), eastern zone, 1985–2018

Sources: Haddon 2017a; AFMA catch disposal records (2017–2018 catch data)

Stock assessment

Orange roughy (east) was managed as a tier 1 stock under the SESSF HSF (AFMA 2017a). The tier 1 assessment by Haddon (2017a), using data up to 2016, underpinned the management of orange roughy (east) for the 2018–19 season. The assumed stock structure is a combination of eastern zone (primarily St Helens Hill and St Patricks Head) and Pedra Branca from the southern zone.

Two base-case models were developed. The first model used a natural mortality of 0.04 and steepness of 0.75 (M = 0.04; h = 0.75), with an estimated spawning biomass of 34%. The second, less productive, model used a natural mortality of 0.036 and steepness of 0.6 (M = 0.036; h = 0.6) and resulted in an estimated spawning biomass of 30%. The consequences of selecting an incorrect base-case model were tested by a risk evaluation. The risk evaluation involved taking the projected catches generated from one model and substituting them into the other model—that is, catches from the more productive base-case model were substituted into the less productive model to test the consequences of erroneously selecting overestimated catches (overestimated catch scenario), and catches from the less productive model were substituted into the more productive model to test the consequences of erroneously underestimating catches (underestimated catch scenario). Results from the overestimated catch scenario indicated a cessation of recovery and ongoing depletion from about 2027. In the underestimated catch scenario, the stock recovery would gradually recover and possibly reach the target of 0.48B0 by 2050 (Haddon 2017a).

The 2017 assessment produced an RBC of 1,314 t for the 2018–19 fishing season, including Pedra Branca (AFMA 2018b; Haddon 2017a). The spawning stock depletion was at approximately 34% of unfished levels (0.34SB0) (Figure 9.36). AFMA recommended a TAC of 698 t, which was the first year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.36 Estimated female spawning stock biomass for orange roughy, eastern zone, 1980–2016

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Haddon 2017a

Stock status determination

The 2017 assessment estimates that eastern zone orange roughy has rebuilt to above the limit reference point (0.34B0). On this basis, the eastern zone orange roughy stock is classified as not overfished.

For the 2018–19 fishing season, the RBC was 1,314 t (AFMA 2018b). The landed catch and discards combined were 859 t, which was below the RBC of 1,314 t. This indicates that the fishing mortality in 2018–19 is unlikely to deplete the stock to a level below its biomass limit reference point. Based on this information, eastern zone orange roughy is classified as notsubject to overfishing.

Orange roughy, southern and western zones

Catch history

The southern and western orange roughy fisheries show similar catch trends to the eastern zone fishery, with a brief period of high catches when fishing first commenced (1989–1992 for the eastern and southern zones; 1986–1988 for the western zone) and low catches thereafter (Figures 9.37 and 9.38). The peak catch in the southern zone was 35,430 t in 1990, with subsequent catches of 14,426 t in 1991 and 16,054 t in 1992 (Figure 9.37). The western zone produced a peak historical catch of 5,128 t in 1987 (Figure 9.38).

The southern and western zone stocks were declared overfished and placed under the ORCP in 2006, subsequently replaced by the ORRS (AFMA 2015b). Targeted commercial fishing ceased at this time, and catch was limited by incidental catch allowances.

In the 2018–19 fishing season, 78.5 t of orange roughy was landed from the southern zone and 19 t from the western zone. Weighted average discards (2014–2017) were 38.7 t in the western zone and zero in the southern zone. There are no state catches (Castillo-Jordán et al. 2018).

FIGURE 9.37 Orange roughy catch (CTS), southern zone, 1985–2018

Sources: Various, including AFMA catch disposal records

FIGURE 9.38 Orange roughy catch (CTS), western zone, 1985–2018

Sources: Various, including AFMA catch disposal records

Stock assessment

The assessment for the southern zone has not been updated since 2000. Standardised catch-per-shot abundance indices, using only data from vessels that had regularly fished this zone, estimated the abundance in 2001 to be 7% of unfished levels (0.07SB0) (Wayte 2002). Because there has been no update to the stock assessment, the RAG continues to advise an RBC of zero.

The last accepted assessment of the western zone was in 2002. The 2002 assessment projected that there was a greater than 90% probability that the 2004 biomass would be less than 30% of the 1985 biomass. In 2017, a preliminary age-based surplus production model was applied to the stock (Haddon 2018), which indicated a potential recovery in the stock, with a spawning biomass depletion of 32% (0.32SB0) estimated for 2015. This preliminary model was not recommended for use in management, but the improvement in spawning biomass it indicated suggested the potential for further sampling and exploration of the condition of the stock. No evidence has been found of spawning aggregations in this region. A comparison of the age composition in 1994–1996 with that in 2004 showed a marked reduction in the modal age, indicating a heavily fished stock, although it is uncertain whether all the otolith samples were from the same stock.

Noting recovery of the eastern zone orange roughy stock, and a long period of low TACs in the southern and western zones, the RAG considered that the southern and western zones may be showing some level of recovery (AFMA 2015d). However, the RAG continues to advise an RBC of zero.

For the 2018–19 season, AFMA set incidental catch allowances of 84 t for the southern zone and 60 t for the western zone (AFMA 2018b).

Stock status determination

The previous assessments of orange roughy in the southern and western zones (Wayte 2002) estimated that the stocks were substantially depleted. Based on this information, the southern and western zone stocks remain classified as overfished.

However, given the time that has passed since stocks were fished and the recovery that has been detected in the eastern stock, it is possible that similar rebuilding has occurred in the southern and western zones. This suggests increasing uncertainty around the biomass status of the southern and western zone orange roughy stocks, and the preliminary age-based surplus production model for the western zone stock supports this. In the absence of additional information on stock status, it is possible that future biomass status may be classified as uncertain.

Given that catches in the southern and western zones are below the incidental catch, and the closure of most areas deeper than 700 m to trawling, orange roughy in the southern and western zones is classified as not subject to overfishing.

Smooth oreodory (Cascade Plateau and non–Cascade Plateau) (Pseudocyttus maculatus)

Smooth oreodory (Cascade Plateau and non–Cascade Plateau (Psuedocyttus maculatus)

Line drawing: FAO

Stock structure

Little is known about the stock structure of smooth oreodory. For assessment and management purposes, smooth oreodory is treated as a single stock throughout the SESSF, excluding the Cascade Plateau and South Tasman Rise, which are managed as separate stocks.

Catch history

Smooth oreodory is targeted in aggregations around seamounts below 600 m, in the same areas as orange roughy. Oreodories have a lower value than orange roughy and historically were not the preferred species. This resulted in some discarding during the 1990s and 2000s, the period of peak orange roughy fishing.

Catches of smooth oreodory on the Cascade Plateau reached maximum levels of 275–300 t in 1997, 2000, 2001 and 2002, but have otherwise generally remained below 100 t (Figure 9.39). There was zero catch in the 2016–17, 2017–18 and 2018–19 seasons. In contrast, annual smooth oreodory catches in other areas exceeded 500 t from 1990 to 1995, reaching almost 1,000 t in 1991 and peaking at 2,390 t in 1992 (Figure 9.40). Catches have been low in the intervening period; however, the recent opening of the Pedra Branca area to orange roughy fishing meant that catches of smooth oreodory increased (AFMA 2018b). Catch increased to 57.7 t in the 2017–18 season and 74.2 t in the 2017–18 season. Weighted average discards between 2014 and 2017 were zero for the Cascade stock and 3.07 t for non-Cascade stocks; there are no state catches (Castillo-Jordán et al. 2018).

FIGURE 9.39 Smooth oreodory annual catches (CTS) and fishing season TACs, Cascade Plateau, 1989–2018

Notes: TAC Total allowable catch.
Sources: Haddon 2012; AFMA logbook records

FIGURE 9.40 Smooth oreodory annual catches (CTS) and fishing season TACs, non–Cascade Plateau, 1987–2018

Notes: TAC Total allowable catch.
Sources: Haddon 2012; AFMA logbook records

Stock assessment

Smooth oreodory on the Cascade Plateau and non–Cascade Plateau smooth oreodory were previously managed as tier 4 stocks under the SESSF HSF (AFMA 2017a). However, because of low catches, the CPUE standardisations were considered unreliable (AFMA 2018b).

For the 2018–19 fishing season, there was no RBC for Cascade Plateau smooth oreodory. The current low effort and catches (less than 10 t per year since 2009) meant that a tier 4 would be unreliable and would recommence when catches increased to above this level (AFMA 2018b). Instead, a TAC of 150 t was implemented until catches reach the 10 t trigger (AFMA 2018b).

A 2015 tier 5 assessment by CSIRO (Haddon et al. 2015) underpinned the management of non–Cascade Plateau smooth oreodory for the 2018–19 fishing season. The assessment produced an RBC of 90 t. The tier 5 approach uses a depletion-based stock reduction analysis (DBSRA) and a weight-of-evidence approach to develop an RBC. Using this method, the yield level predicted to be sustainable is dependent on the median value selected for the expected state of depletion in the final year of the analysis. Using the DBSRA in this manner for the non–Cascade Plateau smooth oreodory stock, and assuming it at the target depletion level of 0.48B0, it was determined that a catch of 90 t should prevent the stock from falling below the limit reference point of 20% (0.2B0) and would keep the stock above 0.35B0 at least 90% of the time. It was considered plausible that the stock was not below a depletion level of 0.48B0 because almost all the stock is deeper than 700 m, which has been closed to fishing since 2007 (Haddon & Sporcic 2017b).

Stock status determination

For the Cascade Plateau stock, the low catches since 2002 and, more recently, since 2009 mean that CPUE is unlikely to be a reliable indicator of abundance. However, it is unlikely that recent low catches have resulted in any substantial change in abundance. For the non–Cascade Plateau stock, the DBSRA assumed that the current depletion level is 0.48B0, which was considered plausible, given the recent low levels of catch and that almost all the stock is deeper than 700 m and not currently available to the fishery. Therefore, the smooth oreodory (Cascade Plateau and non–Cascade Plateau) stocks are both classified as not overfished.

There was no catch of Cascade Plateau smooth oreodory in 2018–19. The total catch of non–Cascade Plateau smooth oreodory was below the RBC. On this basis, both stocks of smooth oreodory are classified as not subject to overfishing.

Other oreodories (warty—Allocyttus verrucosus, spikey—Neocyttus rhomboidalis, rough—N. psilorhynchus, black—A. niger, other—Neocyttus spp.)

Other oreodories (warty—Allocyttus verrucosus, spikey—Neocyttus rhomboidalis, rough—N. psilorhynchus, black—A. niger, other—Neocyttus spp.)

Line drawing: FAO

Stock structure

Other oreodories are a multispecies stock comprising a number of species, including warty oreodory, spikey oreodory, rough oreodory and black oreodory. They are benthopelagic species, caught mainly below 600 m. Little is known about the stock structure of these species; they are treated as a single stock for assessment and management purposes (Morison et al. 2013).

Catch history

Catch peaked in the mid to late 1990s, but has since declined to around 100 t in recent years and was 81 t in 2018–19 (Figure 9.41).

Other oreodories have historically been caught as a byproduct of fishing for orange roughy. Closure of substantial areas deeper than 700 m (except the Cascade Plateau) to all trawling in 2007 under the ORCP and then the ORRS reduced the opportunity to target oreodories.

Although oreodories are generally considered to be a byproduct of other deepwater fisheries, and much of the deepwater habitat is now closed, catches of these species declined substantially before closures were implemented. It is likely that there was substantial but unquantified discarding during the peak of the orange roughy fishery from 1989 to 1992. However, improving the basis for assessing the status of other oreodories is a low priority, given the protection afforded by current deepwater closures.

Weighted average discards over the period 2014–2017 were 256.8 t, and there were no reported state catches (Castillo-Jordán et al. 2018).

FIGURE 9.41 Other oreodories annual catches (CTS) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch.
Sources: Haddon & Sporcic 2017b; AFMA logbook records

Stock assessment

The other oreodories stock was managed as a tier 4 stock under the SESSF HSF (AFMA 2017a).

The standardised CPUE and associated tier 4 assessment by Haddon and Sporcic (2017b) underpinned the management of other oreodories for the 2018–19 season. In previous analyses, the majority (89%) of the catch is reported as spikey oreodory (Sporcic 2015), so the CPUE series may largely reflect the status of spikey oreodory. There is some uncertainty about the reliability of standardised CPUE as an indicator of biomass for this highly aggregating and multispecies stock.

Standardised CPUE declined steadily from 1998 to 2006 in the 2017 analyses, but has since stabilised, remaining near the target CPUE (Figure 9.42). The recent average CPUE (2013–2016) was above the target CPUE, and the 2017 tier 4 assessment produced an RBC of 256 t (Haddon & Sporcic 2017b). Discards were included in the standardisations.

The TAC for the 2018–19 season was set at 185 t, which was the first year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.42 Standardised CPUE for other oreodories, 1986–2016

Note: CPUE Catch-per-unit-effort.
Source: Haddon & Sporcic 2017a

Stock status determination

Since the CPUE has remained stable near the target level, other oreodories are classified as not overfished.

Total landings were 81 t, weighted average discards were 256.8 t, and no state catches were reported. The total fishing mortality in 2018–19 was 337 t, which is above the RBC of 256 t and the TAC of 185 t. This indicates that the fishing mortality rate in 2018–19, if maintained, may deplete the stock to a level below the limit reference point. However, given that current indications of stock size (standardised CPUE) indicate that the stock is near the target reference point, the management agency has some time to control total mortality. On this basis, the fishing mortality status of the stock is classified as uncertain.

Brickle curtain
Lee Georgeson, ABARES

Pink ling (Genypterus blacodes)

Pink ling (Genypterus blacodes)

Line drawing: Rosalind Poole

Stock structure

Clear and persistent differences are seen between the eastern and western areas for pink ling in catch-rate trends, size and age (Morison et al. 2013). This indicates that there are either two separate stocks, or that exchange between eastern and western components of the stock is low and they should be managed as separate stocks. Although genetic variation between eastern and western pink ling has not been found (Ward et al. 2001), the persistent differences in other biological characteristics and catch-rate trends have resulted in pink ling being assessed as separate stocks east and west of longitude 147°E since 2013.

Catches of pink ling are managed under a single TAC. However, AFMA has management arrangements in place to constrain catches of the eastern stock to the eastern catch limit.

Catch history

Combined eastern and western catches of pink ling increased steadily from the start of the fishery in about 1977 to reach a peak of 2,412 t in 1997 (Figure 9.43). Despite TACs continuing to increase from 1997 to 2001, catches declined steadily to about 1,800 t in 2004. From 2004–05 to 2013–14, pink ling catches were limited by the TAC. Commonwealth-landed catch in the 2018–19 fishing season was 952 t, comprising approximately 372.2 t for the eastern stock and 479.9 t for the western stock (according to logbook data and excluding the GABTS). The weighted average discards between 2014 and 2017 were 35.2 t for eastern pink ling and 24.1 t for western pink ling (Castillo-Jordán et al. 2018). State catches were 63.0 t for eastern pink ling and 0.05 t for western pink ling (Castillo-Jordán et al. 2018).

FIGURE 9.43 Pink ling annual catches (CTS, SHS and state combined) and fishing season TACs, 1977–2018

Notes: TAC Total allowable catch. Data for 2013–2018 do not include state data.
Sources: Cordue 2013; AFMA catch disposal records (2013–2018 catch data)

Stock assessment

Pink ling was managed as a tier 1 stock under the SESSF HSF (AFMA 2017a). The tier 1 assessment by Cordue (2015) underpinned the management of pink ling for the 2018–19 season.

Because of complexities in controlling catch of the stock, pink ling is managed under a harvest strategy that uses projections of stock response to various levels of catch and the risk that those catches may pose to breaching the limit reference point. This approach is taken while trying to pursue targets for the western stock and rebuild the eastern stock.

The 2015 assessment produced an RBC of 250 t for the eastern stock and 990 t for the western stock (AFMA 2018e). For the eastern stock, projections of stock response to various constant-catch scenarios indicated that catches below 550 t posed a relatively low (<10%) risk (Table 9.3; Cordue 2015). Subsequently, AFMA set a TAC for the eastern stock of 500 t (AFMA 2018e).

The assessment estimated the median biomass depletions for the two stocks in 2015 to be 0.30B0 for the eastern stock (Figure 9.44) and 0.72B0 for the western stock (Figure 9.45).

An updated assessment (Cordue 2018) estimated the median biomass depletions in 2018 to be 0.35B0 for the eastern stock and 0.84B0 for the western stock.

The total RBC for the 2018–19 fishing season was 1,240 t (AFMA 2018b). The TAC for the 2018–19 season applied for the eastern and western stocks combined was 1,117 t, which was the third year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.44 Estimated spawning stock biomass for eastern pink ling, 1970–2015

Source: Cordue 2015

FIGURE 9.45 Estimated spawning stock biomass for western pink ling, 1970–2015

Source: Cordue 2015

TABLE 9.3 Base-case 2015 stock assessment performance indicators for eastern pink ling, showing stochastic projections at a range of future constant catches

Annual
catch (t)

B2017/B0

B2022/B0

Probability

B2017<0.2B0

Probability

B2022<0.2B0

Rebuild

year

0

0.38

0.63

0

0

2020

300

0.35

0.48

0.01

0

2023

400

0.33

0.43

0.02

0.01

2026

500

0.31

0.38

0.04

0.04

2036

550

0.30

0.35

0.07

0.08

>2050

600

0.29

0.32

0.09

0.13

>2050

700

0.27

0.17

0.15

0.28

>2050

Notes: B2017/B0 Predicted biomass ratio in 2017. B2022/B0 Predicted biomass ratio in 2022. B2017<0.2B0 Biomass below 20% B0 in 2017. B2022<0.2B0 Biomass below 20% B0 in 2022. Rebuild year is the projected year for rebuilding to 48% B0.
Source: Cordue 2015

Stock status determination

The 2015 assessment estimated the median biomass depletion for the western pink ling stock at 72% of the unfished biomass, and the median biomass depletion for the eastern pink ling stock at 30% of the unfished biomass. On this basis, both stocks are considered as not overfished, and so the combined stock of pink ling is classified as not overfished.

Western pink ling catch in the 2018–19 fishing season was 480 t (logbook data). Average discards were 24.1 t, and state catch was 0.05 t. The total mortality combined was 504 t, which was below the western RBC of 990 t. The western stock would be classified as not subject to overfishing.

Eastern pink ling catch in 2018–19 was 372 t. Average discards were 35.1 t, and state catch was 63.0 t, bringing the total to 470 t. This exceeds the RBC of 250 t but is below the TAC of 500 t.

Although the total mortality of eastern pink ling in 2018–19 was above the RBC, at that mortality level the probability of the biomass being depleted to below 0.2B0 in 2017 is less than 0.04% (Table 9.3).

In addition, the updated assessment (Cordue 2018) reported that the biomass depletion was 0.35B0 in 2018. Therefore, the eastern stock appears to be recovering since the 2015 assessment under the current approach to TAC setting. On this basis, the pink ling stock is classified as not subject to overfishing.

Redfish (Centroberyx affinis)

Redfish (Centroberyx affinis)

Line drawing: FAO

Stock structure

No formal stock delineation studies of redfish have been undertaken in Australia. Tagging studies suggested a single stock of redfish off New South Wales (Morison et al. 2013). However, studies of mean length-at-age suggest differences in growth rates of redfish from the ‘northern’ and ‘southern’ sectors of the fishery off eastern Australia (Morison et al. 2013). Previous redfish assessments have therefore assumed that the fishery exploits two separate populations, with the boundary between these ‘stocks’ being 36°S (immediately north of Montague Island in New South Wales) (Morison et al. 2013). The evidence for separate stocks was reviewed and considered to be insufficient; hence, the most recent stock assessment (Tuck & Day 2014) assumes a single stock. Status is determined for a single stock in the east coast of the SESSF (zones 10, 20 and 30).

Catch history

Catches of redfish peaked in the late 1970s and early 1980s, with significant discards recorded on top of landed catch. Landed catch has decreased steadily since the late 1990s. Commonwealth-landed catch was 27.4 t in 2017–18 and 30.8 t in 2018–19 (Figure 9.46).

Estimated discards were 226 t in 2009, but have returned to lower levels in recent years, being usually between 20 t and 70 t since 2010 (Castillo-Jordán et al. 2018). Weighted average discards between 2014 and 2017 were 33.75 t, and state catches were 10.03 t (Castillo-Jordán et al. 2018).

The redfish TAC has been progressively reduced since 2000. The TAC was 276 t in the 2011–12 to 2013–14 seasons, 138 t in 2014–15 and 100 t in the 2015–16 to 2018–19 seasons (AFMA 2018b). Annual catches have remained below the TAC since 2000 (Figure 9.46).

FIGURE 9.46 Redfish annual catches (CTS, SHS and state combined) and fishing season TACs, 1975–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 do not include discards and state catch.
Sources: Tuck et al. 2017; AFMA catch disposal records 2017–(2018 catch data)

Stock assessment

Redfish is currently managed under the Redfish Stock Rebuilding Strategy 2016–2021 (AFMA 2016a). The management objective is to rebuild the stock to the limit reference point (0.2SB0) within 27 years (2042), being one mean generation time plus 10 years (that is, 16.7 years plus 10 years; Tuck & Day 2014).

The most recent assessment of redfish was in 2017 (Tuck et al. 2017). The base-case model used by the RAG to provide advice predicted spawning biomass in 2018 to be 8% of unexploited levels (0.8SB0), a decrease from the previous assessment that predicted 11% (0.11SB0) in 2015 (Tuck & Day 2014) (Figure 9.47).

The RBC from the 2017 assessment was zero, and incidental catch TAC was set at 100 t for the 2018–19 season (AFMA 2018b) to cover redfish taken incidentally while targeting other species.

FIGURE 9.47 Estimated female spawning stock biomass for redfish, 1975–2016

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Tuck et al. 2017

Stock status determination

The 2017 assessment estimated spawning stock biomass for redfish at 8% of unfished levels in 2018. On this basis, redfish is classified as overfished.

The spawning biomass appears to have decreased between the 2014 and 2017 assessments, despite mortality being constrained below the incidental catch allowance. Although mortality may have been constrained to less than the incidental catch allowance (100 t) and the projections that allow for recovery, total mortality for the 2017–18 season is unknown, and recruitment is variable and uncertain. Therefore, the stock remains classified as uncertain if subject to overfishing.

Ribaldo (Mora moro)

Ribaldo (Mora moro)

Line drawing: FAO

Stock structure

One stock of ribaldo is assumed for assessment and management purposes in the SESSF (Morison et al. 2013).

Catch history

Ribaldo is largely taken as byproduct during fishing for other species; only 5% of the catch is considered to be targeted (Klaer et al. 2013). Similar proportions of the annual catch are taken by trawl and line. Historical catches increased from low levels in 1990 to a peak of more than 200 t in 2003. Commonwealth-landed catch dropped in 2005 to about 100 t, following implementation of a TAC, and remained below 100 t until 2018–19, when 107.3 t was taken (Figure 9.48). Weighted average discards between 2014 and 2017 were 5.4 t, and state catches were 2.7 t (Castillo-Jordán et al. 2018).

FIGURE 9.48 Ribaldo annual catches (CTS and SHS) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 do not include discards.
Sources: Haddon & Sporcic 2017b; AFMA catch disposal records (2017–2018 catch data)

Stock assessment

Ribaldo was managed as a tier 4 stock under the SESSF HSF (AFMA 2017a).

The standardised CPUE and associated tier 4 assessment by Haddon and Sporcic (2017b) underpinned the management of ribaldo for the 2018–19 season (Figure 9.49). The 2017 analyses used 1995–2004 as the reference period (when catches first approached 100 t), and produced an RBC of 430 t using the B40 target (AFMA 2018b; Haddon & Sporcic 2017b). An updated CPUE standardisation in 2018 (with data to 2017) showed that CPUE had remained stable (Sporcic & Haddon 2018a).

The TAC for the 2018–19 season was set at 430 t, which was the first year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.49 Standardised CPUE for ribaldo, 1986–2016

Note: CPUE Catch-per-unit-effort.
Source: Haddon & Sporcic 2017b

Stock status determination

Standardised CPUE has remained stable and has been above the target level for the past decade. On this basis, ribaldo is classified as not overfished.

For the 2018–19 fishing season, the total landed catch and discards combined were 115 t, which is below the RBC of 430 t. This indicates that the fishing mortality in 2018–19, if maintained, is unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Royal red prawn (Haliporoides sibogae)

Royal red prawn (Haliporoides sibogae)

Line drawing: FAO

Stock structure

Royal red prawn is widespread, occurring in depths of 350–550 m in the Indian and western Pacific oceans. In Australia, royal red prawn is caught off New South Wales, Queensland and Western Australia between latitudes 10°S and 36°S. Little is known of the stock structure in eastern Australia. Because most of the Australian catch is taken off the New South Wales coast between Port Stephens and Ulladulla, these populations are assumed to comprise a single stock for assessment and management purposes (Morison et al. 2013). The sustainability of stocks outside the SESSF (such as those in Western Australia) is not assessed here.

Catch history

Catch of royal red prawn fluctuated around 500 t per year during the 1990s and early 2000s, before declining and stabilising at a level between 100 and 200 t in recent years (Figure 9.50). Catch has been below the TAC in recent years, which can largely be attributed to limited availability of processing facilities for this species and low market demand (Morison et al. 2013). The catch of royal red prawn in the 2018–19 fishing season was 147 t. Weighted average discards between 2014 and 2017 were 12.8 t, and state catch was 9.3 t (Castillo-Jordán et al. 2018).

FIGURE 9.50 Royal red prawn annual catches (CTS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 do not include discards and state catch.
Sources: Haddon & Sporcic 2017b; AFMA catch disposal records 2017–(2018 catch data)

Stock assessment

Royal red prawn was managed as a tier 4 stock under the SESSF HSF (AFMA 2017d). SERAG has provided advice on the RBC using the B40 target reference point (AFMA 2017d).

The standardised CPUE and associated tier 4 assessment by Haddon and Sporcic (2017b) underpinned the management of royal red prawn for the 2018–19 season. The recent four-year average CPUE is marginally below the target reference point (Figure 9.51).

The 2017 analyses produced an RBC of 431 t (AFMA 2018b; Haddon & Sporcic 2017b). Some concerns about using a standardised CPUE for this stock have been expressed by SERAG because targeting of royal red prawn is market driven (Morison et al. 2013). Such practices may influence CPUE and the application of the SESSF tier 4 harvest control rule.

The TAC set for the 2018–19 season was 381 t, which was the first year of a three-year MYTAC (AFMA 2018b).

FIGURE 9.51 Standardised CPUE for royal red prawn, 1986–2016

Note: CPUE Catch-per-unit-effort.
Source: Haddon & Sporcic 2017a

Stock status determination

The recent average CPUE is marginally above the target reference point. As a result, this stock is classified as not overfished.

Total catch and discards combined were 169 t. This is below the RBC for the stock of 431 t. This indicates that the fishing mortality in 2018–19, if maintained, is unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Silver trevally (Pseudocaranx georgianus)

Silver trevally (Pseudocaranx georgianus)

Line drawing: FAO

Stock structure

Silver trevally is found in Australian and New Zealand waters. In Australia, it ranges from northern New South Wales, around southern Australia to Western Australia. Little is known of the stock structure, but angler tag–recapture studies on Australia’s south-east coast indicate restricted post-settlement movement, potentially leading to ecological stock structuring over moderate (hundreds of kilometres) distances (Fowler, Chick & Stewart 2018). This research supports the contention that silver trevally off south-eastern Australia represents a single stock that is distinct from the fishery off the North Island of New Zealand (Rowling & Raines 2000). The growth rate of the Australian stock of silver trevally is slower than that reported for the New Zealand stock; however, it matures comparatively early, at about two years of age, with spawning occurring throughout summer (Morison et al. 2013).

Catch history

High CPUE between 1989 and 1991, corresponding with a peak catch in 1990 of 1,588 t, was the result of efficient vessels entering the fishery in 1989 (Haddon 2013). Catch has since declined (Figure 9.52). The Commonwealth-landed catch in the 2018–19 fishing season was 8.3 t. State catch was 123.2 t, and weighted average discards between 2014 and 2017 were 29.9 t (Castillo-Jordán et al. 2018).

Silver trevally is also a popular target for recreational fishers off south-eastern Australia; the recreational catch in New South Wales was estimated to be around 27 t in 2013–14 (West et al. 2015).

FIGURE 9.52 Silver trevally annual catches (CTS, SHS and state combined) and fishing season TACs, 1986–2018

Notes: TAC Total allowable catch. Data for 2017 and 2018 exclude discards and state data.
Sources: Haddon & Sporcic 2017b; AFMA catch disposal records (2017–2018 catch data)

Stock assessment

Silver trevally is managed as a tier 4 stock under the SESSF HSF (AFMA 2017a).

The current TAC was set based on application of the SESSF tier 4 harvest control rule to the CPUE analysis completed in 2017 (Haddon & Sporcic 2017b). This found the recent average CPUE to be halfway between the target and limit reference points, and produced an RBC of 445 t (Haddon & Sporcic 2017a; Figure 9.53). This was converted to a MYTAC of 307 t and applied to the 2018–19 fishing season.

The establishment of Batemans Marine Park in June 2007 has affected the estimation of silver trevally RBCs because historical catch data from within the park boundaries are included in the target catch range component of the RBC calculation, but the CPUE analyses do not include historical activities in this area. The RBC derived from the 2013 analysis (Haddon 2013) considered CPUE from both within and outside the marine park, and found little difference in the RBC estimate. The RBC derived from the latest 2017 analysis (Haddon & Sporcic 2017b) excluded all data from the marine park. ShelfRAG recommended waiving the default tier 4 discount factor of 15% of the RBC, on the basis that the marine park provides enough precaution as a refuge for spawning adults and juveniles across a significant portion of the species’ distribution (AFMA 2013, 2018a). However, adult silver trevally are highly mobile, and the inclusion of past marine park catches in RBC calculations assumes that silver trevally in these areas are fully available to fisheries outside the park.

Before 2010, most of the silver trevally catch was taken in state waters outside the SESSF (Morison et al. 2013). The closure of silver trevally trawling grounds within Batemans Marine Park, and the New South Wales buyout of state fishing businesses before 2007, have resulted in a sharp decline in New South Wales state catch (Morison et al. 2013).

FIGURE 9.53 Standardised CPUE for silver trevally, 1986–2016

Note: CPUE Catch-per-unit-effort.
Source: Haddon & Sporcic 2017a

Stock status determination

The recent average CPUE was above the limit reference point. As a result, silver trevally is classified as not overfished.

The landed catch and discards combined were 161.4 t, which is below the RBC of 445 t. This indicates that the fishing mortality in 2018–19, if maintained, is unlikely to deplete the stock to a level below its biomass limit reference point. The stock is therefore classified as not subject to overfishing.

Silver warehou (Seriolella punctata)

Silver warehou (Seriolella punctata)

Line drawing: FAO

Stock structure

A study on the stock structure of silver warehou using genetics (mitochondrial DNA), morphology, otolith shape and otolith microchemistry did not indicate the presence of separate stocks east and west of Bass Strait, although there were indications of some structuring around Tasmania (Robinson et al. 2008). This study, together with other information, suggests that silver warehou should be considered as a single biological stock in the SESSF (Morison et al. 2013).

Catch history

Silver warehou has been a targeted species throughout most of the history of the fishery. Silver warehou catches steadily increased from the start of the fishery to peaks of 4,450 t in 2002 and 4,435 t in 2004 (Figure 9.54). Catches subsequently declined to 276 t in 2015–16 and 311 t in 2016–17.

The TAC in 2018–19 (600 t) was the final year of a three-year MYTAC, which saw the TAC steadily reduce from 2,417 t in 2015–16 (AFMA 2018b).

The Commonwealth-landed catch in the SESSF for the 2018–19 fishing season was 351.6 t. State catch was 1 t, and weighted average discards between 2014 and 2017 were 73.2 t (Castillo-Jordán et al. 2018).

FIGURE 9.54 Silver warehou annual catches (CTS, SHS and state combined) and fishing season TACs, 1980–2018

Notes: TAC Total allowable catch. Data for 2018 do not include discards and state catch.
Sources: Burch et al. 2019; AFMA catch disposal records (2018 catch data)

Stock assessment

Silver warehou is managed as a tier 1 stock under the SESSF HSF, with a target reference point of 0.48B0. The most recent assessment in 2018 (Burch et al. 2019) projected the 2019 spawning biomass to be 0.31B0 under the base-case scenario (assuming average recruitment) (Figure 9.55). This was a reduction from the 2015 assessment (Thomson, Day & Tuck 2015), which predicted the spawning biomass to be 0.4B0 in 2016. The major changes from the 2015 assessment to the 2018 assessment were new tuning methods (Francis weighting), inclusion of catch data from the Gillnet Hook and Trap Sector and the Small Pelagic Fishery, incorporation of discarded catch estimates from factory trawlers when these vessels had observers under the Integrated Scientific Monitoring Program, removal of the fishery-independent survey abundance index from the base case, and not estimating recruitment in 2015 (AFMA 2018c). The application of the SESSF tier 1 harvest control rule to the base-case scenario (assuming average recruitment) generated an RBC of 942 t for 2019–20 (Burch et al. 2019).

Previous silver warehou assessments (Tuck & Fay 2010) estimated that historical recruitment has been fluctuating around average, with a number of years of high recruitment, resulting in the use of an ‘average’ recruitment scenario in projections. Subsequent assessments have estimated that recruitment has been mostly below average since 2003, repeatedly revising recent recruitment estimates downwards (AFMA 2018e). The most recent assessment in 2018 (Burch et al. 2019), using data to 2017, confirmed that biomass has been below the target since 2009, and estimated that it declined to near the 0.20B0 limit from 2014 to 2017.

The 2018 stock assessment (Burch et al. 2019) undertook projections based on two scenarios of below-average recruitment—a ‘poor’ recruitment scenario (the average of a recent five-year period of poor recruitment) and a ‘very poor’ recruitment scenario (the average of the worst three of these five years). A constant catch based on current levels (348 t) was used in projections under these scenarios. Under the assumption of average recruitment (base-case scenario), the return to target is estimated at about 2030, while projections under the poor recruitment scenario indicate that spawning biomass continues to increase, but more slowly than the base case. Under the very poor recruitment scenario, projections show that spawning biomass plateaus at 27% of virgin stock biomass between 2019 and 2023 (AFMA 2018c, e). While the 2018 assessment predicted above-average recruitment, given ‘overly optimistic’ previous assessments, SERAG agreed to use the ‘poor’ recruitment scenario to provide RBC advice, which suggested that catches below 600 t would allow the biomass to rebuild (AFMA 2018c, e).

The TAC for 2019–20 was set at 450 t, a reduction of 150 t from the previous fishing season.

FIGURE 9.55 Estimated spawning stock biomass for silver warehou, 1980–2017

Notes: BCURRENT Current biomass. BREF Unfished biomass.
Source: Burch et al. 2019

Stock status determination

The 2015 stock assessment predicted spawning biomass in 2016 to be 0.4B0 and therefore above the limit reference point. Catches since 2015 are unlikely to have reduced the stock to below the limit reference point. Silver warehou therefore remains classified as not overfished.

Total landed catch and discards combined were 425.8 t in 2018–19, which was below the RBC of 604 t. Catches below 600 t mean that the biomass is expected to gradually improve, and that the risk of falling below the limit reference point is low. This indicates that, if future biomass is stable and the fishing mortality in 2018–19 is maintained, the stock is unlikely to be depleted to a level below the biomass limit reference point. The stock is therefore classified as not subject to overfishing.

9.3 Economic status

Key economic trends

The CTS and the SHS contributed approximately 55% of total SESSF GVP ($76.42 million) in 2017–18. From 2007–08 to 2012–13, real GVP for the two sectors averaged $68.53 million (in 2017–18 dollars; Figure 9.56). By 2013–14, it had fallen, and has since remained below $55 million. Since 2007–08, declines in the value of blue grenadier and silver warehou catches have been the key drivers of the reduction in scalefish GVP. In 2007–08, silver warehou catches were valued at $3.77 million, and blue grenadier catches were valued at $13.44 million. By 2017–18, the GVP of silver warehou catches had declined to $566,000, and blue grenadier catches had declined to $2.80 million. In terms of value during 2017–18, the mix of stocks caught was dominated by tiger flathead ($15.78 million; 33% of total GVP) and pink ling ($5.05 million; 11%).

FIGURE 9.56 Real GVP, by key stocks, for the CTS and the SHS, 2008–09 to 2017–18

Note: GVP Gross value of production.

Estimates of net economic returns (NER) associated with scalefish catches for the CTS and the SHS combined are not available, because ABARES undertakes economic surveys of the CTS separately from the SHS (which is surveyed as part of the GHTS). However, with respect to value, the CTS accounts for most of the scalefish catch. ABARES economic surveys of the CTS estimate that NER in the CTS in 2013–14 were –$1.19 million (Bath, Mobsby & Koduah 2018). This was the first time they had been negative since 2004–05. The low NER were driven by low fishing income in the fishery as a result of an 11% decline in catch from 2012–13, as well as lower unit prices. NER rose to reach $4.0 million by 2016–17 as a result of a fall in operating costs that exceeded a slight fall in fishing income (Mobsby forthcoming). The increase in NER in this period was supported by improvements in fishers’ terms of trade. Preliminary estimates from the survey suggest that NER were –$0.17 million in 2017–18 (Figures 9.57 and 9.58). NER are estimated to have decreased in 2017–18 because lower levels of income to 2016–17 are expected and operating costs are estimated to be higher as a result of higher levels of effort (trawl-hours and shots) in the fishery combined with higher unit fuel prices.

FIGURE 9.57 NER for the CTS, by financial year, 2007–08 to 2017–18

Notes: NER Net economic returns. Results for 2017–18 are preliminary, non–survey based estimates.

FIGURE 9.58 Revenue and costs for the CTS, by financial year, 2007–08 to 2017–18

Note: Results for 2017–18 are preliminary, non–survey based estimates.
Source: Mobsby forthcoming

Management arrangements

Stocks in both the CTS and the SHS are managed under ITQs. TACs are set for key target stocks for each fishing season and allocated to quota holders. This form of management promotes efficiency, because it allows operators to harvest with greater flexibility (with fewer restrictions on inputs), and often results in quota being acquired by the most efficient and profitable operators. ITQ management in the SESSF has used MYTACs for some stocks, which are usually set for three years.

Historically, proxy targets have been set at the stock level and have not taken account of interactions between stocks caught in the sector. If management settings are based on the maximum economic yield (MEY) of individual stocks, achieving the objective for one stock may be constrained by the management settings targeting the MEY of another stock. Under the revised Commonwealth Fisheries Harvest Strategy Policy (Department of Agriculture and Water Resources 2018), all key commercial stocks are required to be managed to a biomass level that achieves overall MEY for the fishery, while byproduct stocks are not required to be managed to MEY. This recognises that it is not feasible to set MEY targets for all species caught in a multispecies fisheries and allows management to focus its efforts on optimising the returns gained from key commercial stocks.

Performance against economic objective

The Commonwealth Fisheries Harvest Strategy Policy allows biomass at MEY (BMEY) targets to be set for key commercial stocks (most often 0.48B0). Tiger flathead, blue grenadier, pink ling and blue-eye trevalla were key commercial stocks caught in 2017–18, and accounted for 63% of total scalefish GVP in both sectors in 2017–18. The biomass of these stocks, relative to the respective BMEY targets, therefore provides an indication of performance against the objective of maximising NER.

Of the four key stocks, only tiger flathead has a quantitatively estimated stock-specific MEY target, at 0.38B0. This was adjusted to 0.40B0 to take a more precautionary approach (Morison et al. 2013; Figure 9.17). At 42% of unfished spawning biomass (0.42SB0), the estimated biomass of tiger flathead in 2016 was slightly above the MEY target (Day 2017b). Similarly, at 0.77B0, the biomass estimate for blue grenadier in 2013 was above the target reference point (0.48B0) (Tuck 2013; Figure 9.8). In 2018, an updated stock assessment estimated that the western pink ling stock was 0.84B0, which is significantly above the target reference point; however, in the east, the stock was 0.35B0, which is below the target reference point. The stock of blue-eye trevalla is between the limit and target reference points. Except for eastern pink ling and blue-eye trevalla, it can be concluded that these four key stocks are being managed at levels that are not below BMEY targets. This implies that NER are not constrained by these two stocks, and improvements are possible if the species were fished down towards BMEY. However, for blue grenadier, lower prices in recent years are likely discouraging participation by the factory vessels best suited to exploiting the stock. Quota latency for blue grenadier increased from 32% in the 2013–14 fishing season to 83% in the 2017–18 fishing season and remained high at 81% in the 2018–19 season. This partly reflects a higher TAC for the stock, but may also reflect changed incentives for fishers. Additionally, the availability of the large New Zealand blue grenadier fishery (where the TAC is close to 150,000 t) provides an alternative to those vessels endorsed to fish in New Zealand (Bath, Mobsby & Koduah 2018). The disinclination of fishers to significantly fish-down blue grenadier suggests that the 0.48B0 proxy may not be aligned with MEY during recent years.

The TAC of some key commercial stocks and many byproduct stocks remained undercaught in the 2018–19 season. Exploring the reasons for undercaught TAC in the fishery has been the focus of recent research for the SESSF fishery. Knuckey et al. (2018) provide a range of potential contributing factors to undercaught TAC for the fishery. The study provides an important reference for management to better understand undercaught TACs in the management context for the fishery.

Vessels could use existing technology more efficiently—the median vessel operated at only 64% efficiency in 2012–13 (Green 2016). Improvements in efficiency would likely improve NER. The same research indicates that potential productivity of the fishery has also declined since 2008–09; more research is required to determine the reasons for this. If it is the result of management changes, the management objectives served by these changes must be assessed against any associated fall in NER.

9.4 Environmental status

The environmental status of these fisheries is discussed in Chapter 8.

Pink ling
Gavin Kewan, AFMA

9.5 References

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—— 2010, ‘Southern and Eastern Scalefish and Shark Fishery—Great Australian Bight Resource Assessment Group (GABRAG) meeting, final minutes, 12–14 October 2010, Adelaide’, AFMA, Canberra.

—— 2012, Upper-slope dogfish management strategy, AFMA, Canberra.

—— 2013, ‘Southern and Eastern Scalefish and Shark Fishery Shelf Resource Assessment Group (ShelfRAG), minutes, 4–5 November 2013, Tasmania’, AFMA, Canberra.

—— 2014a, Blue warehou (Seriolella brama)stock rebuilding strategy, revised 2014, Southern and Eastern Scalefish and Shark Fishery (SESSF), AFMA, Canberra.

—— 2014b, ‘South East Management Advisory Committee (SEMAC) draft minutes, meeting 14, 30–31 January 2014’, AFMA, Canberra.

—— 2014c, Southern and Eastern Scalefish and Shark Fishery management arrangements booklet May 2014, AFMA, Canberra.

—— 2014d, Species summaries for the Southern and Eastern Scalefish and Shark Fishery, AFMA, Canberra.

—— 2015a, Eastern gemfish (Rexea solandri)stock rebuilding strategy, AFMA, Canberra.

—— 2015b, Orange roughy (Hoplostethus atlanticus)stock rebuilding strategy 2014, AFMA, Canberra.

—— 2015c, ‘Southern and Eastern Scalefish and Shark Fishery Shelf Resource Assessment Group (ShelfRAG), minutes, 23–24 September 2015, Tasmania’, AFMA, Canberra.

—— 2015d, ‘Southern and Eastern Scalefish and Shark Fishery Slope Resource Assessment Group (SlopeRAG), minutes, 23–25 September 2015, Hobart’, AFMA, Canberra.

—— 2016a, Redfish (Centroberyx affinis) stock rebuilding strategy 2016–2021, AFMA, Canberra.

—— 2016b, SESSF total allowable catch recommendations for the 2016–17 fishing year, AFMA, Canberra.

—— 2016c, Stock rebuilding strategies annual reviews. Eastern gemfish stock rebuilding strategy—annual review, South East Resource Assessment Group meeting 2016, AFMA, Canberra.

—— 2017a, Harvest strategy framework for the Southern and Eastern Scalefish and Shark Fishery 2009: amended (March 2017), Canberra.

—— 2017b, SESSF total allowable catch recommendations for the 2017–18 fishing year, AFMA, Canberra.

—— 2017c, Southern and Eastern Scalefish and Shark Fishery management arrangements booklet 2017, AFMA, Canberra.

—— 2017d, ‘Southern and Eastern Scalefish and Shark Fishery South East Resource Assessment Group (SERAG), draft minutes, 8–10 November 2017’, AFMA, Canberra.

—— 2018a, 2018 species summaries for the Southern and Eastern Scalefish and Shark Fishery: for stock assessments completed in 2018 in preparation for the 2019–20 fishing seasons, AFMA, Canberra.

—— 2018b, SESSF total allowable catch recommendations for the 2018–19 fishing year, AFMA, Canberra.

—— 2018c, ‘Southern and Eastern Scalefish and Shark Fishery South East Resource Assessment Group (SERAG), minutes, 19–21 September 2018, Hobart’, AFMA, Canberra.

—— 2018d, ‘Southern and Eastern Scalefish and Shark Fishery South East Resource Assessment Group (SERAG), minutes, 14–16 November 2018, Hobart’, AFMA, Canberra.

—— 2018e, Total allowable catch recommendations for the Southern and Eastern Scalefish and Shark Fishery 2019–20 fishing year, AFMA, Canberra.

—— 2019, Harvest strategy framework for the Southern and Eastern Scalefish and Shark Fishery 2009: amended (2019), AFMA, Canberra.

Bath, A, Mobsby, D & Koduah, A 2018, Australian fisheries surveys report 2018: financial and economic performance of the Southern and Eastern Scalefish and Shark Fishery, ABARES, Canberra.

Burch, P, Day, J, Castillo-Jordán, C & Curin Osorio, S 2019, Silver warehou (Seriolella punctata) stock assessment based on data up to 2017, revised after the SERAG meeting 14–16 November 2018, CSIRO Oceans and Atmosphere, Hobart.

Castillo-Jordán, C 2017, Yield, total mortality values and tier 3 estimates for selected shelf and slope species in the SESSF 2017, draft report to AFMA, CSIRO Oceans and Atmosphere.

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—— & Tuck, G 2018, Blue grenadier (Macruronus novaezelandiae) stock assessment based on data up to 2017 base case, for discussion at SERAG, 14–16 November 2018, Hobart, CSIRO Oceans and Atmosphere.

Colgan, DJ & Paxton, JR 1997, ‘Biochemical genetics and recognition of a western stock of the common gemfish, Rexea solandri (Scombroidea: Gempylidae), in Australia’, Marine and Freshwater Research, vol. 48, no. 2, pp. 103–18.

Cordue, P 2013, Pink ling stock assessment: final ISL model results, Innovative Solutions Ltd, Wellington.

—— 2015, The 2015 stock assessment update for eastern and western pink ling, report to AFMA, Innovative Solutions Ltd, Wellington.

—— 2018, Pink ling stock assessment for 2018, final report to AFMA, Innovative Solutions Ltd, Wellington.

Daley, R, Stevens, J & Graham, K 2002, Catch analysis and productivity of the deepwater dogfish resource in southern Australia, Fisheries Research and Development Corporation project 1998/108, CSIRO Marine and Atmospheric Research, Hobart.

Day, J 2016, Tiger flathead (Neoplatycephalus richardsoni) stock assessment based on data up to 2015, CSIRO Marine and Atmospheric Research, Hobart.

—— 2017a, School whiting (Sillago flindersi) stock assessment based on data up to 2016, vers. 2, 18 December 2017, report to AFMA for SERAG meeting, CSIRO Oceans and Atmosphere, Hobart.

—— 2017b, Updated RBC calculations for tiger flathead (Neoplatycephalus richardsoni) stock assessment based on data up to 2015, CSIRO Marine and Atmospheric Research, Hobart.

Department of Agriculture and Water Resources 2018, Commonwealth Fisheries Harvest Strategy Policy, Department of Agriculture and Water Resources, Canberra.

Department of the Environment 2015, Seriolella brama, Species Profile and Threats Database, Department of the Environment, Canberra.

Elliott, NG & Ward, RD 1994, ‘Enzyme variation in jackass morwong, Nemadactylus macropterus (Schneider, 1801) (Teleostei: Cheilodactylidae), from Australian and New Zealand waters’, Australian Journal of Marine and Freshwater Research, vol. 45, no. 1, pp. 51–67.

Fowler, AM, Chick, RC & Stewart, J 2018, ‘Patterns and drivers of movement for a coastal benthopelagic fish, Pseudocaranx georgianus, on Australia’s southeast coast’, Scientific Reports, vol. 8, no. 16738, doi: 10.1038/s41598-018-34922-6, accessed August 2019.

Gonçalves da Silva, A, Appleyard, S & Upston, J 2012, Orange roughy (Hoplostethus atlanticus) population genetic structure in Tasmania, Australia: testing assumptions about eastern zone orange roughy stock structure, CSIRO Marine and Atmospheric Research, Hobart.

Graham, KJ, Andrew, NL & Hodgson, KE 2001, ‘Changes in relative abundance of sharks and rays on Australian South East Fishery trawl grounds after twenty years of fishing’, Marine and Freshwater Research, vol. 52, pp. 549–61.

Green, R 2016, ‘Measuring boat-level efficiency in Commonwealth fisheries: an example using the Commonwealth Trawl Sector of the Southern and Eastern Scalefish and Shark Fishery’, conference paper, Australian Agricultural and Resource Economics Society Annual Conference, 2–5 February, Canberra.

Haddon, M 2012, Tier 4 analyses in the SESSF, including deep water species: data from 1986–2011, CSIRO Marine and Atmospheric Research, Hobart.

—— 2013, Tier 4 analyses in the SESSF, including deep water species: data from 1986–2012, CSIRO Marine and Atmospheric Research, Hobart.

—— 2014, Tier 4 analyses of selected species in the SESSF: data from 1986–2013, CSIRO Marine and Atmospheric Research, Hobart.

—— 2016, Blue-eye (Hyperoglyphe antarctica) tier 4 analysis using catch-per-hook for auto-line and drop-line from 1997–2015, draft version, CSIRO.

—— 2017a, Orange roughy east (Hoplostethus atlanticus) stock assessment using data to 2016, report to AFMA for SERAG meeting, 8–10 November 2017, CSIRO Oceans and Atmosphere, Hobart.

—— 2017b, Tier 4 assessment for blue-eye trevalla (data to 2016), CSIRO Oceans and Atmosphere, Hobart.

—— 2018, Orange roughy west CPUE 1989–2006, draft, 15 March 2018, CSIRO Oceans and Atmosphere, Hobart.

——, Klaer, N, Wayte, S & Tuck, G 2015, Options for tier 5 approaches in the SESSF when data support for harvest strategies are inappropriate, FRDC project 2013/202, CSIRO Oceans and Atmosphere, Hobart.

—— & Sporcic, M 2017a, Statistical CPUE standardizations for selected SESSF species (data to 2016), report to AFMA for SESSFRAG data meeting, 7–8 August 2017, CSIRO Oceans and Atmosphere, Hobart.

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Hamer, P, Kemp, J, Robertson, S & Hindell, J 2009, Use of otolith chemistry and shape to assess the stock structure of blue grenadier (Macruronus novaezelandiae) in the Commonwealth Trawl and Great Australian Bight fisheries, final report to FRDC, project 2007/020, Fisheries Research Branch, Queenscliff.

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Klaer, N, Day, J, Fuller, M, Krusic-Goleb, K & Upston, J 2013, Data summary for the Southern and Eastern Scalefish and Shark Fishery: logbook, landings and observer data to 2012, CSIRO Marine and Atmospheric Research, Hobart.

——, Day, J, Fuller, M, Krusic-Goleb, K & Upston, J 2014, Data summary for the Southern and Eastern Scalefish and Shark Fishery: logbook, landings and observer data to 2013, CSIRO Marine and Atmospheric Research, Hobart.

Knuckey, I, Boag, S, Day, G, Hobday, A, Jennings, S, Little, R, Mobsby, D, Ogier, E, Nicol, S & Stephenson, R 2018, Understanding factors influencing under-caught TACs, declining catch rates and failure to recover for many quota species in the SESSF, final report to FRDC, project 2016/146, Fishwell Consulting, Queenscliff.

Last, PR & Stevens, JD 2009, Sharks and rays of Australia, CSIRO Publishing, Collingwood.

Little, R 2012, ‘A summary of the spawning potential ratio (SPR), its calculation and use in determining over-fishing in the SESSF: an example with eastern gemfish’, in GN Tuck (ed.), Stock assessment for the Southern and Eastern Scalefish and Shark Fishery 2011, part 2, AFMA & CSIRO Marine and Atmospheric Research, Hobart.

—— 2016, 2010 update of the eastern gemfish (Rexea solandri) stock assessment, CSIRO, Australia.

—— & Rowling, K 2011, ‘2010 update of the eastern gemfish (Rexea solandri) stock assessment’, in GN Tuck (ed.), Stock assessment for the Southern and Eastern Scalefish and Shark Fishery 2010, part 1, AFMA & CSIRO Marine and Atmospheric Research, Hobart.

Miller, MP & Stewart, J 2009, ‘The commercial fishery for ocean leatherjackets (Nelusetta ayraudi, Monacanthidae) in New South Wales, Australia’, Asian Fisheries Science, vol. 22, pp. 257–64.

Mobsby D forthcoming, Australian fisheries surveys report 2018: financial and economic performance of the Southern and Eastern Scalefish and Shark Fishery, ABARES, Canberra.

Moore, A, Ovenden, J & Bustamante, C 2017, Research to underpin better understanding and management of western gemfish stocks in the Great Australian Bight, FRDC project 2013/014, FRDC, Canberra.

Morison, AK, Knuckey, IA, Simpfendorfer, CA & Buckworth, RC (eds) 2012, 2011 stock assessment summaries for the Southern and Eastern Scalefish and Shark Fishery, report to AFMA, Canberra.

——, Knuckey, IA, Simpfendorfer, CA & Buckworth, RC 2013, South East Scalefish and Shark Fishery: draft 2012 stock assessment summaries for species assessed by GABRAG, ShelfRAG & Slope/DeepRAG, report to AFMA, Canberra.

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Robinson, N, Skinner, A, Sethuraman, L, McPartlan, H, Murray, ND, Knuckey, I, Smith, D, Hindell, J & Talman, S 2008, ‘Genetic stock structure of blue-eye trevalla (Hyperoglyphe antarctica) and warehous (Seriolella brama and Seriolella punctata) in south-eastern Australian waters’, Marine and Freshwater Research, vol. 59, no. 6, pp. 502–14.

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Silver trevally
Grant Robinson, AFMA





Last reviewed: 4 November 2019
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