Patagonian Toothfish, *Dissostichus eleginoides* Smitt, 1898.

Patagonian Toothfish, Dissostichus eleginoides Smitt, 1898.



Map of the management areas within the CAMLR Convention Area. Subarea 48.3, the region discussed in this report is shaded in green. Throughout this report, “2020” refers to the 2019/20 CCAMLR fishing season (from 1 December 2019 to 30 November 2020).

Map of the management areas within the CAMLR Convention Area. Subarea 48.3, the region discussed in this report is shaded in green. Throughout this report, “2020” refers to the 2019/20 CCAMLR fishing season (from 1 December 2019 to 30 November 2020).



1. Introduction to the fishery

1.1. History

The fishery for Patagonian toothfish (Dissostichus eleginoides) in Subarea 48.3 began in the 1980s and expanded rapidly during the early 1990s, when considerable illegal, unreported and unregulated (IUU) catches were also taken (Table 1). The initial fishery also caused high rates of incidental bird mortality, with relatively large numbers of albatrosses and petrels attracted to the baited hooks and being caught and drowned. In response to these issues, CCAMLR introduced strict regulations designed to reduce bird by catch. These regulations, including seasonal closures, streamer lines, line-weighting regimes and night-setting requirements, greatly reduced bird by-catch in this fishery. The current toothfish fishery uses demersal longlines in which lines of baited hooks are deployed close to the sea floor at depths down to 2,250 m.


1.2. Conservation Measures currently in force

The limits on the fishery for D. eleginoides in Subarea 48.3 for the forthcoming season are defined in Conservation Measure 41-02.

Figure 1: Location of the Management Areas in Subarea 48.3.

Figure 1: Location of the Management Areas in Subarea 48.3.


1.3. Active vessels

In 2020, 5 vessels participated in this fishery.


1.4. Timeline of spatial management

In 2004, CCAMLR agreed to subdivide Subarea 48.3 into three Management Areas (A, B and C; Fig. 1) defined in Conservation Measure 41-02, Annex 41-02/A.

In 1998, the fishery was restricted to the winter months (1 May to 31 August) to minimise interactions with foraging birds during their breeding season. Since 2010, CCAMLR has applied a gradual extension to the season, accompanied by a number of seabird bycatch limits in those extension periods, the season is now from 16 April to 14 September as set out in Conservation Measure 41-02.


2. Reported catch

2.1. Latest reports and limits

Reported catches of Dissostichus eleginoides are shown in Table 1. In this fishery, the catch of D. eleginoides reached a maximum of 7493 tonnes in 2003. In 2020, 1884 tonnes of D. eleginoides were caught.


Table 1. Catch (tonnes) and effort history for Dissostichus eleginoides in this fishery. Source: Fine scale data and past estimates for IUU catch (-: no IUU estimate available).
Season Number of vessels Catch limit (tonnes) Catch Estimated IUU catch (tonnes)
1980 1 64
1981 1 7
1984 1 3
1986 1 7
1987 1 130
1988 4 584
1989 3 3577
1990 2 5023
1991 1 270
1992 19 3500 3986 3066
1993 19 3350 4018 4019
1994 4 1300 639 4780
1995 13 2800 3082 1674
1996 13 4000 3297 0
1997 10 5000 3724 0
1998 9 3300 2848 146
1999 12 3500 3660 667
2000 16 5310 5067 1015
2001 16 4500 3916 196
2002 17 5820 5453 3
2003 19 7810 7493 0
2004 16 4420 4460 0
2005 9 3050 3030 23
2006 10 3556 3546 0
2007 10 3554 3539 0
2008 12 3920 3862 0
2009 11 3920 3382 0
2010 9 3000 2518 0
2011 6 3000 1732 0
2012 7 2600 1836 0
2013 7 2600 2094 0
2014 7 2400 2180 0
2015 6 2400 2195 0
2016 6 2750 2196 0
2017 6 2750 2195 0
2018 6 2600 1950 0
2019 6 2600 2124 0
2020 5 2327 1884


2.2. By-catch

Annual catch limits for by-catch species groups are defined in Conservation Measures 41-02 and 33-01. If the by-catch of skates or macrourids exceeds 1 tonne in any one haul or set, then the fishing vessel must move at least 5 nautical miles away for a period of at least five days.

Catches of by-catch species groups (macrourids, skates (Rajids) and other species), their respective catch limits and number of skates released alive are summarised in Table 2.


Table 2. Reported catch and catch limits for by-catch species (Macrourus spp., Rajids and others) in this fishery (see Conservation Measure 41-02 for details). Source: fine-scale data.
Macrourus spp.
Rajids
Other catch
Season Catch Limit (tonnes) Reported Catch (tonnes) Catch Limit (tonnes) Reported Catch (tonnes) Number Released Catch Limit (tonnes) Reported Catch (tonnes)
1985 0 0 0 4 0 0 <1
1986 0 <1 0 9 0 0 <1
1987 0 <1 0 3 0 0 <1
1988 0 <1 0 <1 0 0 <1
1989 0 <1 0 11 0 0 <1
1990 0 <1 0 <1 0 0 <1
1991 0 1 0 4 0 0 <1
1992 0 <1 0 2 0 0 <1
1993 0 2 0 <1 0 0 <1
1994 0 <1 0 12 0 0 <1
1995 0 12 0 90 0 0 <1
1996 0 32 0 54 0 0 <1
1997 0 33 0 43 0 0 2
1998 0 21 0 13 0 0 1
1999 0 21 0 19 0 0 <1
2000 0 18 0 12 0 0 2
2001 0 21 0 27 0 0 1
2002 0 50 0 25 0 0 5
2003 0 74 0 37 0 0 10
2004 221 30 221 6 0
3
2005 152 121 152 8 0
19
2006 177 136 177 7 21056
35
2007 177 129 177 4 9265
26
2008 196 161 196 12 19558
36
2009 196 110 196 22 23709
33
2010 150 70 150 7 15810
16
2011 150 74 150 4 12832
9
2012 130 54 130 2 13503
9
2013 130 59 130 2 14005
11
2014 120 61 120 3 12969
15
2015 120 56 120 2 10937
10
2016 138 64 138 2 14960
14
2017 138 54 138 3 12916
16
2018 130 107 130 4 21235
29
2019 130 107 130 3 23817
41
2020 116 87 116 3 23610
47

A preliminary assessment of skate populations in Subarea 48.3 using a surplus production model implemented in a Bayesian framework was presented in 2007 (WG-SAM-07/11), at which time it was considered that there were insufficient data to inform the assessment. Nevertheless, these preliminary results suggested that the by-catch limit in Subarea 48.3 for rajids would be considered sustainable.

A skate tagging program has been under way since 2006 in Subarea 48.3 and a preliminary assessment of skates in Subarea 48.3 using tagging data was presented in 2014 (WG-FSA-14/48). This assessment indicated a stable biomass. Using the same skate tagging programme, a stock status and population assessment of the Antarctic starry skate (Amblyraja georgiana) in Subarea 48.3 was presented in 2018 (WG-FSA-18/27). These results indicated that the longline fishery for toothfish does not appear to have resulted in a decline in the population of A. georgiana and at present has low by-catch rates of exploitation.

Recent genetic analysis of skates (Amblyraja spp.) (WG-FSA-18/73) suggests that skates caught as by-catch from CCAMLR subareas 48.3 and 48.4 that were identified as A. georgiana, A. georgiana sp. anon and A. taaf do not represent distinct, reproductively isolated species. Rather, these different morphological forms of Amblyraja appear to be interbreeding members from two geographically differentiated stocks, one occurring around South Georgia and the other around the South Sandwich Islands (Subarea 48.4).


2.3. Vulnerable marine ecosystems (VMEs)

As Conservation Measure 22-06 does not apply to this subarea there are no CCAMLR VMEs or VME Risk Areas designated in Subarea 48.3. There are fishery-specific restrictions in place to mitigate the impact of the fishery on vulnerable marine ecosystems (VMEs), including benthic communities and benthos such as seamounts, hydrothermal vents and cold-water corals.


2.4. Incidental mortality of seabirds and marine mammals

A summary of seabird mortality in the longline fishery in Subarea 48.3 in recent years is shown in Table 3. The three most common species injured or killed in the fishery since 2005 were southern giant petrel (Macronectes giganteus), white-chinned petrel (Procellaria aequinoctialis) and black-browed albatross (Thalassarche melanophris).

The requirements of Conservation Measure 25-02 ‘Minimisation of the incidental mortality of birds in the course of longline fishing or longline fishing research in the Convention Area’ apply to this fishery in addition to the seasonal closure and the night-setting requirements described in Conservation Measure 41-02.

The risk level in this fishery in Subarea 48.3 is category 5 (high) (SC CAMLR-XXX, Annex 8, paragraph 8.1).

Table 3. Number of reported birds caught (killed or with injuries likely to substantially reduce long-term survival) in this fishery in each fishing season.
Season Macronectes giganteus Procellaria aequinoctialis Thalassarche melanophris Other
1992 4
1995 122 597 39 176
1996 5 102 297 291
1997 13 198 253 122
1998 37 8 6
1999 1 42 62 5
2000 1 1
2001 1
2003 2 1 1
2004 1
2005 1
2009 1 1
2010 2
2011 1
2012 1 1
2013 1 1
2014 77
2015 1
2016 30
2017 19 1
2018 1 22 1 1
2019 1
2020 1


A summary of mammal mortalities associated with longline fishing in Subarea 48.3 is given in Table 4.

Table 4. Number of reported mammals killed in this fishery in each fishing season.
Season Arctocephalus gazella Hydrurga leptonyx Leptonychotes weddellii Mirounga leonina Otariidae, Phocidae Physeter catodon
1995 1
1996 1 1
1997 3
1998 1
2004 1
2007 2
2009 1 1
2012 1
2014 1


3. Illegal, Unreported and Unregulated (IUU) fishing

There has been no reported evidence of IUU fishing activities in Subarea 48.3 since 2006 (Table 1).


4. Data collection

4.1. Data collection requirements

The collection of biological data is conducted in accordance to Conservation Measure 23-05. The collection of biological data as part of the CCAMLR Scheme of International Scientific Observation (SISO) includes representative samples of length, weight, sex and maturity stage, as well as collection of otoliths for age determination of the target and most frequently taken by-catch species.


4.2. Length frequency distributions

Recent length frequency distributions for catches of D. eleginoides in Subarea 48.3 are shown in Figure 2. These length frequency distributions are unweighted; they have not been adjusted for factors such as the size of the catches from which they were collected. The interannual variability exhibited in the figure may reflect changes in the fished population but is also likely to reflect changes in the gear used, the number of vessels in the fishery and the spatial and temporal distributions of fishing.


Figure 2. Annual length frequency distributions of *D. eleginoides* caught in Subarea 48.3. The number of hauls from which fish were measured (N) and the number of fish measured (n) in each year are indicated. Letters to the left of the panel (B and C) refer to the management areas shown in Figure 1. Note: length frequency distributions are only shown where more than 150 fish were measured.

Figure 2. Annual length frequency distributions of D. eleginoides caught in Subarea 48.3. The number of hauls from which fish were measured (N) and the number of fish measured (n) in each year are indicated. Letters to the left of the panel (B and C) refer to the management areas shown in Figure 1. Note: length frequency distributions are only shown where more than 150 fish were measured.


4.3. Tagging

Tagging of D. eleginoides is conducted at a rate of 1.3 fish per tonne in this fishery; a total of 60971 D. eleginoides have been tagged and released and 10836 have been recaptured, 10124 of which were released in this area (Table 5).


Table 5. Number of Dissostichus eleginoides tagged and recaptured in the area for each fishing Season.
Recaptured
Season Tagged 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Total
2004 3218 25 97 129 116 109 51 36 31 16 4 16 9 9 6 6 2 3 665
2005 3949 23 194 155 148 121 86 45 24 39 26 17 19 25 11 10 5 948
2006 4889 31 227 197 146 132 73 51 52 43 20 13 22 16 12 12 1047
2007 4782 41 239 172 139 82 64 56 51 36 21 30 17 16 14 978
2008 4632 61 235 150 107 81 79 69 48 49 43 35 38 14 1009
2009 3506 19 138 71 67 66 60 52 32 40 22 29 16 612
2010 2966 12 72 62 48 55 39 40 32 19 17 17 413
2011 2909 18 98 89 81 64 59 48 32 42 25 556
2012 3027 19 118 98 79 73 53 37 33 36 546
2013 3356 17 126 89 93 90 53 63 37 568
2014 3563 34 126 129 106 72 70 48 585
2015 3718 15 170 143 98 119 83 628
2016 3515 35 194 111 107 109 556
2017 3486 41 169 140 127 477
2018 3381 27 154 119 300
2019 3159 24 169 193
2020 2915 43 43
Total 60971 10124


5. Research

In January-February 2019, the UK undertook a random stratified bottom trawl survey of South Georgia and Shag Rocks (see WG-FSA-2019/20). The survey used the same trawl gear and survey design as previous UK surveys in Subarea 48.3 (see WG-FSA-15/26 and WG-FSA-17/44). The 2019 survey covered the whole shelf area, covering depths of 100-350m. The primary aim of the survey was to estimate stocks of mackerel icefish (Champsocephalus gunnari) but juvenile D. eleginoides were also captured. Numbers and lengths of D. eleginoides provide an index of recruitment for stock assessments.

Dissostichus eleginoides were caught in 28 of the 73 hauls in the 2019 survey and were, as in previous surveys, present in greatest numbers around the eastern and western ends of the Shag Rocks shelf. Toothfish ranged in length from 18 to 117 cm, with evidence of a 1+ cohort with a mode at 18-26 cm.

All toothfish vessels in Subarea 48.3 carry a CCAMLR scientific observer who collects a range of data on toothfish and common by-catch, including conversion factors, length frequencies, weights and maturity. Toothfish otoliths are collected by observers for an ageing program that provides length-at-age data for assessments. Observers also record whale occurrence at the vessel during hauling; data which is then used to model depredation rates which are included in the stock assessment. Observers work with vessels to tag toothfish and skates and collate recapture data.

Dissostichus eleginoides in Subarea 48.3 are genetically distinct from those found on the Patagonian shelf (FAO Area 41). The stock, occurring within Management Areas A, B and C, is genetically separate from fish taken in the extreme north and west of Subarea 48.3 and the assessments consider only the stock within Management Areas A, B and C (further details of the stock assessment are provided in the Stock Assessment Annex).

6. Stock status

6.1. Summary of current status

Assessment of the Patagonian toothfish (D. eleginoides) in Subarea 48.3 indicates that the current status of the stock is at 50% of B0. Spawning biomass has been relatively constant in recent years (WG-FSA-19/28).


6.2. Assessment method

The stock of D. eleginoides in Subarea 48.3 was assessed using an age-structured, two-fleet, CASAL integrated stock assessment model (WG-FSA-19/28).


6.3. Year of last assessment, year of next assessment

Assessments are reviewed biennially, the last assessment was in 2019.


7. Climate Change and environmental variability

A recent summary of the potential impacts of climate change on Southern Ocean fisheries (FAO 2018) highlights the following key points:

The Antarctic region is characterized by complex interaction of natural climate variability and anthropogenic climate change that produce high levels of variability in both physical and biological systems, including impacts on key fishery taxa such as Antarctic krill.

The impact of anthropogenic climate change in the short-term could be expected to be related to changes in sea ice and physical access to fishing grounds, whereas longer-term implications are likely to include changes in ecosystem productivity affecting target stocks.

There are no resident human populations or fishery-dependent livelihoods in the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Area, therefore climate change will have limited direct implications for regional food security. However, as an “under-exploited” fishery, there is potential for krill to play a role in global food security in the longer term.

The institutional and management approach taken by CCAMLR, including the ecosystem-based approach, the establishment of large marine protected areas, and scientific monitoring programmes, provides measures of resilience to climate change.

There is no formal evaluation of the impacts of climate change and environmental variability available for this particular fishery.


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