Chapter 27: CCAMLR Exploratory Toothfish Fisheries
H Patterson and K Mazur
TABLE 27.1 Status of the CCAMLR Exploratory Toothfish Fisheries
| Biological status|| Fishing mortality|| Biomass||Fishing mortality||Biomass|| |
|Division 58.4.1, toothfish
(Dissostichus mawsoni)||Not subject to overfishing||Uncertain||Not subject to overfishing||Uncertain||No estimate of current biomass available.|
| || ||Not subject to overfishing||Not overfished||Most recent estimate of biomass is above the limit reference point under the CCAMLR harvest strategy. The TAC is conservative relative to current biomass.|
|Subarea 88.2, toothfish
(Dissostichus mawsoni, D. eleginoides)||Not subject to overfishing||Not overfished||Not subject to overfishing||Not overfished||Most recent estimate of biomass is above the limit reference point under the CCAMLR harvest strategy. The TAC is conservative relative to current biomass.|
|Economic status||Estimates of NER are not available, and NER remain uncertain. Australian fishers participated in subarea 88.2 from the 2014–15 fishing season, in division 58.4.1 from the 2015–16 season and in subarea 88.1 in the 2016–17 fishing season.|
a This stock was not assessed in 2016.
CCAMLR Commission for the Conservation of Antarctic Marine Living Resources.
NER Net economic returns.
TAC Total allowable catch.
27.1 Description of the fishery
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was established in 1982 to conserve and manage the Southern Ocean Antarctic ecosystem. The objective of the CCAMLR is the conservation of Antarctic marine living resources. The CCAMLR Convention area is defined as the area south of the Antarctic Convergence, as well as the area south of 60°S where the Antarctic Treaty (1959) applies (Figure 27.1).
The CCAMLR defines ‘new and exploratory’ fisheries for particular areas, and places emphasis on acquiring biological and other information during the development of the fisheries. Participation in such fisheries requires Member States to implement management measures, and a research plan detailing the scientific data that a country plans to collect and contribute to the CCAMLR.
Exploratory fisheries are defined under Conservation Measure 21-02:
- an exploratory fishery shall be defined as a fishery that was previously classified as a ‘new fishery’, as defined by Conservation Measure 21-01
- an exploratory fishery shall continue to be classified as such until sufficient information is available
- to evaluate the distribution, abundance and demography of the target species, leading to an estimate of the fishery’s potential yield
- to review the fishery’s potential impacts on dependent and related species
- to allow the Scientific Committee to formulate and provide advice to the Commission on appropriate harvest catch levels, as well as effort levels and fishing gear, where appropriate.
The Ross Sea and Amundsen Sea area are encompassed by CCAMLR subareas 88.1 and 88.2 (Figure 27.1). These two subareas are CCAMLR exploratory toothfish fisheries and are managed separately, with distinct stock assessments. Subarea 88.1 was fished in 2016–17 by an Australian vessel for the first time. An Australian vessel nominated to fish in divisions 58.4.1 and 58.4.2 in the 2016–17 fishing season (Figure 27.1), but only division 58.4.1 was fished because of mechanical problems with the vessel.
Fishing methods and key species
Demersal longline is the primary method used to target Antarctic toothfish (Dissostichus mawsoni) and Patagonian toothfish (D. eleginoides) in CCAMLR toothfish fisheries.Before 2017, the exploratory fisheries described here were for Dissostichus spp. (that is, both species). To better align the assessments with the target species, the fisheries now have the sole target species D. mawsoni (noting that, if any D. eleginoides are caught, they are decremented against the catch limit). New and exploratory fisheries have catch limits for bycatch species, such as skates and rays,whiptails (Macrourus spp.) and other species, as well as move-on provisions. The bycatch limits may be based on a percentage of the catch of toothfish (for example, 5 per cent of the catch limit for Dissostichus spp.), or may be set as a specific limit (for example, 50 t) for each CCAMLR subarea or division that constitutes a new and exploratory fishery.
Harvest strategies for the target species are consistent with the precautionary approach implemented by the CCAMLR that has been used to set catch limits since the mid 1990s. The harvest strategy for toothfish developed by the CCAMLR is more precautionary than the guidelines of the Commonwealth Fisheries Harvest Strategy Policy (DAFF 2007). For toothfish, the reference points in the CCAMLR harvest strategy dictate that median escapement of the spawning biomass at the end of a 35-year projection period is 50 per cent of its median pre-exploitation level, and that the probability of the spawning biomass dropping below 20 per cent of its median pre-exploitation level is less than 10 per cent over the projection period. In exploratory fisheries, total allowable catches (TACs) are then fished by approved vessels that have nominated to fish specific subareas. Shares of the toothfish TAC are not allocated to particular CCAMLR members in exploratory fisheries; however, members may receive allocations to conduct specific research programs. Fishing is closed when the catch limit for the subarea is reached, based on daily catch-and-effort reporting that is required by all vessels. Vessels fishing in exploratory fisheries are required to carry scientific observers, and to tag and release toothfish at pre-specified levels as part of the scientific data collection process.
Australia fished subarea 88.1 for the first time in 2016–17, but began fishing in subarea 88.2 in 2014–15. There was no previous effort by Australian vessels in these subareas, although other CCAMLR members have fished them previously. In 2015–16, however, there was no effort in subarea 88.2 by Australian vessels.
Division 58.4.1 was fished for the first time by an Australian vessel in 2015–16 (excluding some experimental trawling in the division in 1999–2000).
TABLE 27.2 Main features and statistics for the CCAMLR exploratory toothfish fisheries
2015–16 fishing season
2016–17 fishing season
|Real value (2014–15)||TAC|
|Real value (2015–16)|
|Division 58.4.1, toothfish||660||51||Confidential||660||10||Confidential|
|Subarea 88.1, toothfish||–||–||–||2,870||81||Confidential|
|Subarea 88.2, toothfish||619||0||Confidential||619||151||Confidential|
|Effort||Division 58.4.1: 348,605 hooks
Subarea 88.1: 0 hooks
Subarea 88.2: 0 hooks
|Division 58.4.1: 123,250 hooks
Subarea 88.1: 33,150 hooks
Subarea 88.2: 347,225 hooks
|Fishing permits||Division 58.4.1: 1
Subarea 88.1: 0
Subarea 88.2: 1
|Division 58.4.1: 1
Subarea 88.1: 1
Subarea 88.2: 1
|Active vessels||Division 58.4.1: 1
Subarea 88.1: 0
Subarea 88.2: 0
|Division 58.4.1: 1
Subarea 88.1: 1
Subarea 88.2: 1
d ||100% vessel coverage||100% vessel coverage|
|Fishing methods||Demersal longline|
|Primary landing ports||Hobart (Tasmania); Nelson (New Zealand)|
|Management methods||Input controls: limited entry, gear restrictions, temporal and spatial closures
Output controls: TACs
Other: move-on provisions if bycatch thresholds are reached
|Primary markets||International: China, Japan, United States—frozen|
|Management plan||No formal management plan; operations consistent with CCAMLR conservation measures|
a Fishery statistics are provided by fishing season, unless otherwise indicated. Season is 1 December to 31 August. Real-value statistics are by financial year.b Total available TAC for all participating fleets.c Australian catch only. Total catches are provided in Figures 27.2, 27.3 and 27.4.d All Australian vessels carry two observers on each trip.
CCAMLR Commission for the Conservation of Antarctic Marine Living Resources.
TAC Total allowable catch. – No Australian vessels participated in the fishery in division 58.4.1 in 2014–15.
27.2 Biological status
Antarctic Toothfish (Dissostichus mawsoni) in subarea 88.1
Line drawing: FAO
Genetic examination of Antarctic toothfish from widely separated CCAMLR statistical areas (Atlantic Ocean sector, Pacific Ocean sector, Indian Ocean sector) has produced mixed results. Early studies found some weak variation by ocean sector (Kuhn & Gaffney 2008; Smith & Gaffney 2005), whereas a more recent study was unable to detect any genetic variation among fish from the different sectors (Mugue et al. 2014). However, tagging studies from numerous locations in the CCAMLR Convention area have indicated that most adult toothfish are sedentary and are recaptured relatively close (<50 km) to where they were tagged (Hanchet et al. 2008; Petrov & Tatarnikov 2010; Welsford et al. 2011). This should result in genetic differentiation. Newer genomic techniques may be needed to better understand stock structure. Preliminary otolith chemistry work has also provided evidence of regional stock structuring (Tana et al. 2014).
The stock assessment boundaries for the Ross Sea (described here) include subarea 88.1, and small-scale research units (SSRUs) A and B from subarea 88.2.
Catches were relatively small in the early years of the fishery, but have increased since 2002 as the TAC has increased (Figure 27.2). Most of the catch has been Antarctic toothfish; Patagonian toothfish has accounted for 5 per cent or less of the catch since 2010.
The most recent full stock assessment of Antarctic toothfish from CCAMLR subarea 88.1, and subarea 88.2 SSRUs A and B was conducted in 2017 using the CASAL integrated assessment model and is a Bayesian sex- and age-structured assessment (Mormede 2017). The assessment included catch data and catch-at-age frequencies from 1998 to 2016 for the three areas of the Ross Sea (shelf, slope and north). In addition, tag–recapture data were included, as were survey-based standardised local abundance and catch-at-age frequencies from the survey of the Ross Sea shelf (Large, Robinson & Parker 2017).
The recommended model estimated the current level of biomass as 72 per cent of unfished levels (B2016/B0 = 0.72; range 0.69–0.75). This is higher than the 2015 estimate of unfished biomass; the difference is likely the result of revised estimates of the effective tag survival and detection rates. The yield that satisfied the CCAMLR decision rules was estimated using a number of options to split the catch between the three areas (shelf, slope and north), or between areas north and south of 70°S and the special research zone of the Ross Sea region marine protected area.
All the estimates for yield (3,213–2,278 t) were higher than the pre-specified catch limit in Conservation Measure 91-05, which gives a range of 2,583–3,157 t as the total catch limit. Given this, a catch limit of 3,157 t for the 2017–18 and 2018–19 seasons was recommended (CCAMLR 2017a, b). Previous research has demonstrated that toothfish stocks that are fished at a rate of 3 per cent of the estimated current biomass are likely to rebuild to the target level within two decades, even if currently near the limit reference point of 20 per cent of unfished biomass (Welsford 2011). The catch limit for subarea 88.1 equates to 4.3 per cent of the estimated current biomass. Given the relatively high estimate of current biomass in subarea 88.1, this TAC is therefore regarded as conservative.
Stock status determination
Given the relatively high spawning biomass, which is above the target reference point under the CCAMLR harvest strategy, the stock is classified as not overfished. The TAC was set at a conservative level based on previous research. Illegal, unreported and unregulated (IUU) fishing has been largely eliminated by enforcement efforts. Given this precautionary approach, the limited entry to the fishery and the extensive CCAMLR review process, the stock is classified as not subject to overfishing.
Antarctic Toothfish (Dissostichus mawsoni) in division 88.2
CCAMLR subarea 88.2 is divided into SSRUs that are labelled A to H. The stock assessment boundaries for the Amundsen Sea region (described here) consider SSRUs C–H to be a distinct stock (Hanchet & Parker 2014; Parker, Hanchet & Horn 2014). It is thought that spawning takes place on the northern seamounts in subarea 88.2 (SSRU H), with the larvae being transported by oceanographic processes to the east (SSRUs F–G).
No catches were reported in the early years of the fishery (1997–2001). Catches have generally increased since 2002 as the TAC has increased (Figure 27.3).
The most recent full stock assessment of Antarctic toothfish from CCAMLR subarea 88.2 SSRUs C–H was conducted in 2013 using the CASAL integrated assessment model (Mormede, Dunn & Hanchet 2013). The assessment included catch data and catch-at-age frequencies from 2003 to 2013 for each SSRU. In addition, tag–recapture data for SSRU H were included because fishing in the other SSRUs has been inconsistent. Constant recruitment was assumed across the SSRUs.
There were some conflicting results among the model runs, with some runs estimating unfished biomass to be lower than that estimated by earlier assessments completed in 2011 and 2013. The conflict was largely driven by the tagging data from SSRU H, which was considered reliable as a result of improved tagging and data collection procedures. In addition, the model runs with a reduced estimate of unfished biomass down-weighted the age data, which were limited and did not include SSRU H, the area from which most of the catch was taken.
The recommended model run down-weighted the age data and used the tagging data (Mormede, Dunn & Hanchet 2013). This model estimated the current level of biomass as 65 per cent of unfished levels (B2013/B0 = 0.65; range 0.52–0.75). This is lower than the 2011 estimate of 82 per cent of unfished biomass, but remains above the target reference point of 50 per cent. The 2013 Working Group on Fish Stock Assessment could not reach consensus on the assessment. It noted that the assessment may not be representative of SSRUs C–G because most of the data driving the results came from SSRU H (CCAMLR 2013).
The CCAMLR Scientific Committee provided updated advice on the TAC in 2014 based on two biomass estimates for SSRU H, using the mark–recapture data and Petersen models (Goncharov & Petrov 2014; Parker & Mormede 2014). These were simple models using tagging data for SSRU H only, and excluded all the other data that would be used in an integrated assessment. They did not provide new biomass depletion estimates for subarea 88.2, and consequently the estimate from the 2013 integrated assessment (65 per cent) remains the best biomass depletion estimate available.
Based on the results of the Petersen models, the TAC for subarea 88.2 SSRUs C–H was set at 619 t, with 200 t designated for SSRU H and the remaining 419 t for SSRUs C–G (CCAMLR 2015a, b). A yield of 619 t equates to 3 per cent of the estimated current biomass. Previous research has demonstrated that toothfish stocks that are fished at a rate of 3 per cent are likely to rebuild to the target level within two decades, even if currently near the limit reference point of 20 per cent of unfished biomass (Welsford 2011). Given the relatively high estimate of current biomass in subarea 88.2, this TAC is therefore regarded as conservative.
Stock status determination
Given the relatively high spawning biomass, which is above the target reference point under the CCAMLR harvest strategy, the stock is classified as not overfished. The TAC was set at a conservative level based on previous research and was fully taken. IUU fishing has been largely eliminated by enforcement efforts. Given this precautionary approach, the limited entry to the fishery and the extensive CCAMLR review process, the stock is classified as not subject to overfishing.
Antarctic toothfish (Dissostichus mawsoni) in division 58.4.1
Toothfish in division 58.4.1 is considered a single stock for management purposes.
CCAMLR division 58.4.1 contains research blocks where exploratory fishing is permitted. Fishing has occurred in the division under licence since 2005, with TACs ranging from 210 to 724 t (Figure 27.4). Australia did not participate in the fishery before 2015–16, although some experimental trawling did occur in 1999–2000.
No reliable and accepted integrated stock assessment is available for division 58.4.1. Although some earlier studies applied different tag-based methods to obtain some indication of stock status, these were considered unreliable because of low tag returns (Agnew et al. 2008). The current level of biomass in division 58.4.1 is therefore unknown.
Fishing in the established research blocks, where previous tagging occurred and is ongoing, is intended to provide data for a future stock assessment. The participation of CCAMLR members in the fishery is restricted, and participants must provide a multiyear research plan that will provide data for a future stock assessment. IUU fishing, which has been a significant problem in CCAMLR toothfish fisheries in the past, has been largely eliminated by international enforcement efforts.
To set catch limits for exploratory fishing, biomass in each research block is estimated independently based on tag recoveries, or mean catch rate compared with an assessed area scaled by the seabed area in the block. The catch limits are then set so that they do not exceed 3–4 per cent of the estimated stock size. Previous modelling work has demonstrated that this level of harvest will likely allow an overfished stock (<20 per cent B0) to recover in the long term (Welsford 2011); it is unknown whether the stock in division 58.4.1 is overfished.
Stock status determination
Given that there is no stock assessment for the entire division and no current overall estimate of biomass, the stock is classified as uncertain for overfished status. The catch limits set for each research block are based on assessed fisheries, and are set to a level low enough that an overfished stock could recover in the long term. The total catch for the division was below the TAC. In addition, IUU fishing has been eliminated, and participation in the fishery has been restrained to a very low level. Given these factors, the stock is considered not subject to overfishing.
27.3 Economic status
Key economic trends
Australia began fishing subarea 88.2 in 2014–15. The total TAC for the subarea was caught in that period—with Australia capturing almost one-third of the TAC—indicating positive net economic returns (NER) for the fishery. Subarea 88.2 was not fished in the 2015–16 fishing season, but 24 per cent of the TAC was caught in this subarea in 2016–17. Australia began fishing division 58.4.1 in the 2015–16 fishing season, catching 8 per cent of the TAC that season, and 2 per cent in the 2016–17 season. Australia began fishing subarea 88.1 in the 2016–17 fishing season, catching 3 per cent of the TAC. Toothfish is a high-value species with well-established markets and supply chains, but fishing is undertaken in remote areas and under difficult operating conditions. Although there is potential for positive NER to be generated by fishers, fishing has been sporadic, indicating some uncertainty for NER.
The CCAMLR harvest strategy requires that the spawning biomass be 50 per cent of pre-fished levels at the end of a 35-year projection period. For subarea 88.2, however, the TAC was set by calculating current biomass and setting the TAC at 3 per cent of that biomass. This has previously been shown to be a precautionary method of setting the TAC, which is likely to allow stocks near the limit reference point to recover to the target level within two decades. A similar method is used to set the TAC for the research blocks in subarea 88.1 and division 58.4.1. Since the current biomass in subarea 88.2 is estimated to be above the target reference point, the TAC is considered conservative. When the TAC is fully caught, the fishery is closed. Given the incomplete catch of the TAC, NER are uncertain in the fishery in a manner that is consistent with the conservative ecological objectives.
27.4 Environmental status
The fishery for toothfish in CCAMLR subareas 88.1 and 88.2 has been assessed as exempt from export controls under the Environment Protection and Biodiversity Conservation Act 1999 until 31 October 2019. The fishery in CCAMLR divisions 58.4.1 and 58.4.2 is exempt until 27 November 2020. No special recommendations were included in the assessments beyond the usual requirements to ensure proper reporting and notification of changes to management arrangements, and to implement relevant CCAMLR conservation measures. No ecological risk assessment has been undertaken for these fisheries.
In the 2016–17 fishing season, no logbook or observer reports noted interactions between an Australian vessel and protected species in the CCAMLR exploratory fisheries.
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CCAMLR 2013, Report of the Working Group on Fish Stock Assessment, WG-FSA-13, Commission for the Conservation of Antarctic Living Marine Resources, Hobart.
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