Patagonian Toothfish, *Dissostichus* *eleginoides* Smitt, 1898.

Patagonian Toothfish, Dissostichus eleginoides Smitt, 1898.



Map of the management areas within the CAMLR Convention Area. The region discussed in this report is shaded in green. Throughout this report, “2024” refers to the 2023/24 CCAMLR fishing season (from 1 December 2023 to 30 November 2024). Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Projection: EPSG 6932.

Map of the management areas within the CAMLR Convention Area. The region discussed in this report is shaded in green. Throughout this report, “2024” refers to the 2023/24 CCAMLR fishing season (from 1 December 2023 to 30 November 2024). Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Projection: EPSG 6932.



1. Introduction to the fishery

1.1. History

This report describes the licensed longline fishery for Patagonian toothfish (Dissostichus eleginoides) in the French Exclusive Economic Zone (EEZ) established in 1978 around the Kerguelen Islands in Division 58.5.1.

The fishery, targeting D. eleginoides, began as a trawl fishery in 1985 but targeting other species between 1979 and 1984 and caught small amounts of toothfish as by-catch. Trawling continued to 2001 and intermittently in 2006 and 2010; a longline fishery began in 1992 (Duhamel et al., 2011). The fishery is active throughout the year with the exception of a summer closure period (1 February to either 1 or 15 March) which has been in place since 2004.

Within the French EEZs, fishing seasons, catch limits for target species, as well as vessel licensing, are allocated by France. Since 2019, catch limits are set for a period of 3 years. The season extends from 1 September to 31 August. French management measures, annually established by TAAF, specific to the EEZ, have restricted the longline fishery to waters outside the 12 nautical mile zone and no shallower than 500m. Fishing is also prohibited within the strict protection areas of the Marine Reserve since 2006.


1.2. Conservation Measures currently in force

No new information was available on the state of fish stocks in Division 58.5.1 outside areas of national jurisdiction and thus the prohibition of directed fishing for D. eleginoides, described in Conservation Measure 32-13, shall remain in force.

Within the French EEZs, catch limits for target species, as well as vessel licensing, are allocated by France. A six-year management plan was adopted in July 2019 with the overall objective of ensuring conditions for a sustainable and optimal exploitation of Patagonian toothfish. It also sets catch limits for a period of 3 years. The 2020-2022 seasonal catch limit was set at 5200 tonnes, and the 2023-2025 seasonal catch limit was set at 5020 tonnes.

In the EEZ of Kerguelen, various national conservation and fisheries enforcement measures are applicable, such as:

  • Annual catch limit set triennially since September 2019
  • Demersal longlines and pots are the only authorized fishing gears
  • Fishing season extends from 1 September to 31 August of the following year with an annual closure from 1 February to mid-March, which differs from the CCAMLR fishing season
  • One vessel at a time fishing per 0.5\(^{\circ}\) latitude x 1\(^{\circ}\) longitude rectangle for a maximum period of 10 days
  • Fishing is prohibited within the strict protection areas of the Marine Reserve which include areas not exceeding 500m in depth
  • Move-on rule to limit catches of D. eleginoides of 60cm and less
  • Cut-off procedure and move-on rules for skates to reduce fishing mortality
  • Mitigation measures to reduce bird mortality
  • Move-on rule on VME
  • One French scientific observer on board each licensed vessel
  • Mandatory vessel logbooks
  • A single catch landings site at Réunion Island
  • Mandatory port inspection
Figure 1: Map of the region discussed in this report. Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Bathymetry: GEBCO. Projection: EPSG 6932 (rotated).

Figure 1: Map of the region discussed in this report. Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Bathymetry: GEBCO. Projection: EPSG 6932 (rotated).


1.3. Active vessels

In 2024, 9 vessels participated in this fishery.


2. Reported catch

Since the CCAMLR fishing season (1 December to 30 November of the following year, UTC time) and the TAAF fishing season (1 September to 31 August of the following year) do not match, data pooled at the annual scale and shown in this document may not match data reported by TAAF. This distinction is particularly relevant if readers wish to compare annual catch in the Convention Area to annual catch limits as set by TAAF.

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 9126 tonnes in 2000. In 2024, 4856 tonnes of D. eleginoides were caught.


Table 1. Catch and effort history for Dissostichus eleginoides in this fishery. Source: Fine scale data and past estimates for IUU catch (-: no fishing, or no IUU estimate available).
Season Longline Catch (tonnes) Trawl Catch (tonnes) Pot Catch (tonnes) Total Catch (tonnes) Number of vessels Estimated IUU catch (tonnes)
1992 – 1588 – 1588 1 –
1993 – 1570 – 1570 1 –
1994 – 4348 – 4348 1 –
1995 – 3997 – 3997 1 –
1996 – 3304 – 3304 1 833
1997 – 4011 – 4011 1 6094
1998 121 3525 – 3645 1 7156
1999 504 3617 – 4121 5 1237
2000 2999 6127 – 9126 8 2600
2001 2589 4348 – 6937 8 4550
2002 4075 346 – 4421 11 6300
2003 5452 – – 5452 7 5518
2004 5099 0 – 5099 9 536
2005 5034 – – 5034 7 268
2006 4698 254 – 4952 8 144
2007 5345 – – 5345 7 451
2008 4859 – – 4859 7 720
2009 5238 – – 5238 8 0
2010 4915 235 – 5151 8 22
2011 5236 – – 5236 7 –
2012 4904 – – 4904 7 –
2013 5377 – – 5377 7 –
2014 5326 – – 5326 7 –
2015 4392 – – 4392 8 –
2016 5553 – – 5553 8 –
2017 5098 – – 5098 9 –
2018 4878 – – 4878 7 –
2019 5270 – – 5270 7 –
2020 5157 – – 5157 7 –
2021 5038 – 1 5039 7 –
2022 5196 – 0 5196 7 –
2023 5115 – – 5115 9 –
2024 4856 – – 4856 9 –



2.2. By-catch

Primary by-catch species from the longline fishery in the French EEZ in Division 58.5.1 are the macrourid Macrourus carinatus, rajid skates (Bathyraja irrasa and B. eatonii) and blue antimora (Antimora rostrata). The latter species is fully discarded, while the others are partly or totally retained. The spatial distribution of by-catch indicates specific areas of higher catch rates that differed between species (WG-FSA-10/34).

The catch histories for by-catch species are provided in Table 2.


Table 2. Reported catch for by-catch species (Macrourus spp., skates and Antimora rostrata) in this longline fishery. Source: fine-scale data.
Macrourus spp.
Skates
Antimora rostrata
Season Reported Catch (tonnes) Reported Catch (tonnes) Number Released Reported Catch (tonnes)
1998 12 12 0 <1
1999 37 42 0 1
2000 162 120 0 1
2001 97 116 0 <1
2002 448 530 0 2
2003 772 929 0 10
2004 938 1133 0 12
2005 779 975 0 47
2006 686 596 0 54
2007 779 546 1954 56
2008 821 376 3593 68
2009 956 415 3432 45
2010 884 455 2 59
2011 861 438 535 52
2012 691 433 15878 26
2013 727 308 12423 67
2014 752 68 32808 72
2015 605 9 33641 69
2016 696 13 53270 56
2017 642 22 44273 49
2018 665 22 44225 38
2019 523 15 52044 43
2020 445 24 62187 60
2021 716 26 60386 94
2022 693 16 50380 88
2023 710 16 57074 90
2024 558 14 50127 76


No stock assessments of individual by-catch species are presently undertaken, but biomass of a part of the stocks is now available from the biomass surveys (POKER 2006, 2010, 2013, 2017; Duhamel et al., 2019) and could help in the future. The Working Group on Fish Stock Assessment (WG-FSA) recommended that, where possible, areas with high by-catch rates should be avoided, particularly those shown in WG-FSA-09/43. The requirement for rajids to be ‘cut-off’ at the surface has been in force since 2014.

2.3. Vulnerable marine ecosystems (VMEs)

All Members are required to submit, within their general fisheries notifications requirements, information on the known and anticipated impacts of their gear on vulnerable marine ecosystems (VMEs), including benthic communities and benthos such as seamounts, hydrothermal vents and cold-water corals. All of the VMEs in CCAMLR’s VME Registry are currently afforded protection through specific area closures.

In this fishery, fishery observers collect information about benthic taxa, including those considered as VME taxa.

As Conservation Measure 22-06 does not apply to this area, there are no VMEs or VME Risk Areas designated in Division 58.5.1.


2.4. Incidental mortality of seabirds and marine mammals

CCAMLR mitigation measures are applied in the French EEZ. A summary of the historic bird mortality by longline in the French EEZ in Division 58.5.1 is shown in Table 3. The most common species injured or killed in the fishery was white-chinned petrel (Procellaria aequinoctialis). Night-setting requirements have been highly effective in removing the previously high levels of albatross mortality.

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 halli Procellaria aequinoctialis Procellaria cinerea Other
2007 3 57 10 1
2008 5 271 14
2009 2 111 6
2010 5 63 15 1
2011 9 49 8 1
2012 41 5 1
2013 6 18 2
2014 4 2
2015 1 9 3
2016 12 7
2017 13 1
2018 9
2019 22
2020 7
2021 27 4
2022 1
2023 1 34 1
2024 13 2

The level of risk of incidental mortality of birds in Division 58.5.1 is category 5 (high) (SC-CAMLR-XXX, Annex 8, paragraph 8.1).

France applies the requirements of Conservation Measure 25-02 ‘Minimisation of the incidental mortality of seabirds in the course of longline fishing or longline fishing research in the Convention Area’ to this fishery.

Additional measures are also applied (WG-IMAF-11/10 Rev. 1), including:

  1. changes to the bird exclusion device to ensure it is effective in all weather conditions,

  2. closure of fishing areas and quota allocation reduction for vessels that have high by-catch rates,

  3. education and training is strengthened by regular meetings between TAAF and fishing masters of vessels with high by-catch,

  4. data will continue to be collected and submitted using CCAMLR standard methods and forms,

  5. a demographic study on the white-chinned petrel will be undertaken at Kerguelen Islands, as well as the continued population counts of white-chinned petrels on the Kerguelen archipelago.


To date, most mammal IMAF incidents reported in this fishery involved Southern elephant seals (Mirounga leonina; Table 4).

Table 4. Number of reported mammals killed or with injuries likely to substantially reduce long-term survival in this fishery in each fishing season. N.B. Data prior to 2021 were collected but not reported (reporting of number started in September 2020).
Season Arctocephalus gazella Mirounga leonina
2022 4
2023 3
2024 1 4


3. Illegal, Unreported and Unregulated (IUU) fishing

Illegal, unreported and unregulated (IUU) fishing was first detected in this region in 1996 and in some years IUU catches have exceeded legal catches, resulting in total removals exceeding 10,000 tonnes in some seasons.

IUU fishing activity was detected in Division 58.5.1 (Kerguelen EEZ) during 2006, with one IUU-listed fishing vessel observed in the division. Two IUU-listed vessels were sighted during 2007 and three IUU-listed vessels were sighted during 2008. One IUU fishing vessel was observed on the boundary of the Kerguelen EEZ during winter 2007, and reports from France indicate that IUU activities sometimes occurred here during each year from 2008 to 2012. One IUU-listed fishing vessel was sighted in Division 58.5.1 during 2010, two during 2012 and one during the 2013. No IUU-listed vessels were observed during 2014, 2015 and 2016, however, IUU fishing gear was recovered from the region during all three years. Following the recognition of methodological issues in its assessment, no estimates of the IUU catch of Dissostichus spp. have been provided since 2011 (SC-CAMLR-XXIX, paragraph 6.5).


4. Data collection

4.1. Data collection requirements

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. Summary of available data

Both the vessel’s crew and observers collect fishing effort, catch, and by-catch information.

The vessel’s crew report total catch of by-catch by coarse taxonomic groups given the taxonomic expertise required to discriminate similar species. Observers collect biological information on toothfish and by-catch specimens at a finer taxonomic resolution, and report toothfish length measurements to CCAMLR.

Summaries of data reported to CCAMLR for the past five years are given in Tables 5 and 6.

Table 5. Summary of by-catch and biological data reported by vessels crew and observers in each of the last five seasons in this longline fishery. By-catch records correspond to the number of observations of total weight and count of individuals for each taxon identified. Taxonomic identification may occur at different levels. N.B. Data prior to 2021 were collected but not reported (reporting of weight, sex, maturity, gonad weight and otolith samples started in September 2021).
Data source Data class Variable 2020 2021 2022 2023 2024
Vessel crew by-catch taxa identified 9 9 13 13 14
records 8943 10271 9249 11460 10403
Observer toothfish specimens examined 119084 130880 136678 155609 158364
length measurements 119084 130880 136629 155607 158340
weight measurements 0 499 2604 1943 5322
sex identifications 0 18886 96772 111366 98596
maturity stage identifications 0 18886 96671 104395 97849
gonad weight measurements 0 0 62 36 72
otolith samples 0 514 2398 1847 702
Table 6. Summary of biological data for predominant by-catch groups reported by observers (from random subsets of lines) in each of the last five seasons. Taxonomic identification may occur at different levels. N.B. Data prior to 2021 were collected but not reported (reporting started in September 2021).
By-catch group Variable 2020 2021 2022 2023 2024
Macrourus spp. specimens examined 0 2218 7306 8537 8583
taxa identified 0 1 3 2 1
length measurements 0 2218 7296 8468 7903
weight measurements** 0 24 221 81 70
snout to anus measurements* 0 2135 5743 7362 8166
sex identifications** 0 461 760 2679 3950
maturity stage identifications** 0 79 469 1292 1527
gonad weight measurements** 0 0 0 0 0
otolith samples** 0 24 107 88 22
Skates and rays specimens examined 0 934 2074 1273 1274
taxa identified 0 2 2 3 4
length measurements 0 934 2073 1267 1273
weight measurements** 0 41 671 448 349
wingspan measurements* 0 214 1016 1033 820
pelvic length measurements* 0 0 489 162 342
sex identifications** 0 933 1926 1269 1270
maturity stage identifications** 0 197 1043 707 568
gonad weight measurements** 0 0 0 0 0
Other fish specimens examined 0 1249 2721 3731 3354
taxa identified 0 3 5 10 10
length measurements 0 1249 2696 3716 3345
weight measurements** 0 37 128 177 150
standard length measurements* 0 22 66 276 129
sex identifications** 0 311 191 422 139
maturity stage identifications** 0 52 57 258 11
gonad weight measurements** 0 0 0 0 0
otolith samples** 0 36 104 64 37
**: Voluntary records
*: Species-dependent records


The counts of by-catch taxa reported above (Table 6) correspond to specimens that have been individually sampled by observers. These are a subset of all the specimens counted by observers and are generally identified at a more precise taxonomic level. The figures below (Figs. 2 and 3) display the distribution of the most frequently examined by-catch taxa in time and space. It is important to note that observers sample a random subset of lines and do not individually examine all taxa; as such these figures are more representative of the distribution of biological observations than the catch of these taxa or their spatial distribution. At a coarse taxonomic level, the total catch of by-catch species groups is provided in section 2.2 above.

Figure 2. Relative frequencies of the most commonly examined by-catch taxa in each of the last five seasons, from the observer data (unweighted raw counts of individually examined specimens). Taxonomic identification may occur at different levels. *N.B.* Data prior to 2021 were collected but not reported (reporting started in September 2021).

Figure 2. Relative frequencies of the most commonly examined by-catch taxa in each of the last five seasons, from the observer data (unweighted raw counts of individually examined specimens). Taxonomic identification may occur at different levels. N.B. Data prior to 2021 were collected but not reported (reporting started in September 2021).


Figure 3. Spatial distribution of the most commonly examined by-catch taxa across the last five seasons, from the observer data (unweighted raw counts of individually examined specimens in each cell). The data were aggregated using equal area (100 km x 100 km) cells. Taxonomic identification may occur at different levels. Refer to Figure 1 for more details on the boundaries shown. Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Bathymetry: GEBCO. Projection: EPSG 6932 (rotated). *N.B.* Data prior to 2021 was collected but not reported (reporting started in September 2021).

Figure 3. Spatial distribution of the most commonly examined by-catch taxa across the last five seasons, from the observer data (unweighted raw counts of individually examined specimens in each cell). The data were aggregated using equal area (100 km x 100 km) cells. Taxonomic identification may occur at different levels. Refer to Figure 1 for more details on the boundaries shown. Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Bathymetry: GEBCO. Projection: EPSG 6932 (rotated). N.B. Data prior to 2021 was collected but not reported (reporting started in September 2021).


4.3. Length frequency distributions

The recent length frequency distributions of D. eleginoides caught in this fishery are presented in Figure 4 (only commercial longline considered). The majority of D. eleginoides caught by longline range from 50 to 125cm in length, with a single strong mode for all seasons at approximately 70cm. 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 4. Annual length frequency distributions of *D.* *eleginoides* caught by longline in this fishery. The number of hauls from which fish were measured (N) and the number of fish measured (n) in each year are indicated. Note: length frequency distributions are only shown where more than 150 fish were measured.

Figure 4. Annual length frequency distributions of D. eleginoides caught by longline in this fishery. The number of hauls from which fish were measured (N) and the number of fish measured (n) in each year are indicated. Note: length frequency distributions are only shown where more than 150 fish were measured.


4.4. Tagging

Within the French EEZ, vessels are required to tag and release toothfish at a rate of 1 fish per tonne of green weight caught throughout the season.

To date in this area, 86936 D. eleginoides have been tagged and released (14514 have been recaptured, 14255 of which were released in this area; Table 7).

Table 7. Number of Dissostichus eleginoides tagged and recaptured in the area for each fishing Season.
Recaptured
Season Tagged 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 Total
2006 636
2007 2258 12 58 62 52 37 26 16 11 12 7 6 3 3 1 1 2 309
2008 2479 18 87 77 52 46 36 16 12 6 7 9 4 5 2 1 2 380
2009 4367 42 116 118 107 93 48 26 23 19 13 4 8 4 3 624
2010 4880 27 122 132 121 79 45 49 33 21 12 15 9 6 8 1 680
2011 5378 42 243 236 154 107 98 54 46 40 17 18 14 18 1 1 1089
2012 4987 55 209 180 145 131 72 52 46 25 23 20 21 6 1 986
2013 5445 72 211 171 161 120 86 60 44 41 21 14 8 1 1010
2014 5400 44 181 203 135 100 87 50 45 42 21 11 3 922
2015 4503 60 194 197 112 95 69 57 36 23 9 852
2016 5631 80 199 265 186 121 92 58 43 28 3 1075
2017 5194 73 250 257 219 126 81 61 33 3 1103
2018 4760 43 301 256 159 104 80 50 5 998
2019 5399 85 339 231 183 147 92 16 1093
2020 5236 94 326 205 194 134 14 967
2021 5136 92 291 324 199 17 923
2022 4882 99 295 186 31 611
2023 5307 134 290 48 472
2024 5058 109 52 161
Total 86936 14255

The tagging program undertaken by France in its EEZ in Division 58.5.1 has achieved a similar tag-recapture rate to the tagging program undertaken by Australia in Division 58.5.2, which indicates that tagged fish move mainly short distances, but some fish make longer forays around the slope, as well as long-distance movements outside the Division. Fish from the tagging program at Heard Island (Division 58.5.2) have also shown movement of sub adult/adult fish between zones (Heard to Kerguelen and also Crozet), but the proportion of exchange between stocks is relatively small (Williams et al., 2002; WG-FSA-07/48 Rev. 1).

5. Research

Four biomass survey cruises (named POKER 1, 2, 3 and 4) have been conducted in 2006 (Duhamel and Hautecoeur, 2009), 2010 and 2013 (see WG-FSA-14/07) and 2017 respectively to estimate biomass and recruitment of D. eleginoides on the whole shelf and surrounding banks (100-1,000m). Such surveys are planned to be conducted every 3 to 4 years.

Collaborative work between France and Australia on analyses of catch, effort and other data (survey, tagging) to be used to progress understanding of fish stocks and fishery dynamics for Divisions 58.5.1 and 58.5.2 is ongoing (see WG-SAM-11/20, WG-SAM-15/37).

In 2019, catch removals due to killer and sperm whale interactions across subantarctic fisheries were estimated (WG-FSA-2019/33). These estimates are routinely updated as part of the stock assessment (WG-FSA-2021/46).

In 2022, WG-FSA-2022/19 presented an analysis of skate handling practices and condition assessment methods in the longline toothfish fisheries operating in the southern Indian Ocean. Results provided clear guidelines for crew members operating on longline vessels to maximise the survival of released skates. WG-FSA-2022/20 presented a preliminary study on the use of the vertebrae centrum in the age determination of skates (Amblyraja taaf in Crozet, and, Bathyraja eatonii and B. irrasa in Kerguelen waters).

In 2023, WG-FSA-2023/11 presented results from an aging study using the centrum of 285 vertebrae for the three skate species caught as by-catch in the Kerguelen and Crozet Patagonian toothfish fisheries in Division 58.5.1 and Subarea 58.6. WG-FSA-2023/35 further presented length-at-maturity estimates for B. eatonii and B. irrasa in Kerguelen and A. taaf in Crozet. WG-FSA-2023/28 explored how different recruitment projections under potential regime shifts in Patagonian toothfish stocks might influence associated SSB calculations, and, an investigation into whether re-estimation of SSB0 according to stock productivity (dynamic SSB0) might impact historical, current and future stock status.

In 2024, WG-FSA-IMAF-2024 considered a large work program for integrated toothfish stock assessments, with a focus on the performance of the decision rules, the effects of spatial bias in tagging data, approaches to select recruitment data for stock status projections, and management strategy evaluations (WG-FSA-IMAF-2024, paragraphs 4.30–4.50). Papers summarising this work included WG-SAM-2024/17, WG-SAM-2024/22, WG-SAM-2024/23, WG-SAM-2024/24, WG-SAM-2024/25 and WG-FSA-IMAF-2024/47. The stock assessment for this fishery was updated a part of the stock assessment workplan (SC-CAMLR-43, paragraphs 3.7–3.8).

6. Stock status

6.1. Summary of current status

According to the 2024 assessment (WG-FSA-IMAF-2024/67), SSB0 is estimated at 188,460 tonnes (95% CI: 175,690–203,010 tonnes). The estimate of the current SSB status of the stock is 56.4% (95% CI: 54.2–60.2%).


6.2. Assessment method

The stock in this fishery was assessed using a fully integrated single-sex Casal2 model.


6.3. Year of last assessment, year of next assessment

Assessments are reviewed biennially during WG-FSA, the last assessment was in 2024.


7. Climate Change and environmental variability

In 2022, the Commission recognised that climate change is already having effects in the Convention Area (CCAMLR-41, paragraph 6.3) and agreed that it needed to act urgently to prepare for, and adapt to, the effects of climate change on the marine ecosystems within the Convention Area (CCAMLR-41, paragraph 6.5). The Commission noted (CCAMLR-41, paragraph 6.4) that the Scientific Committee had incorporated climate change into its advice (SC-CAMLR-41, paragraph 7.8) and through discussions at the SC-Symposium (SC-CAMLR-41, Annex 11) had also added climate change to the work plans and terms of reference of its Working Groups (SC-CAMLR-41, paragraph 7.14). The Commission adopted (CCAMLR-41, paragraph 6.28) Resolution 36/41.

In 2023, the Scientific Committee held a workshop on Climate Change (WS-CC-2023) which made recommendations regarding monitoring and management actions CCAMLR could progress to document and track the effects of climate change in the Convention Area. The recommendations were incorporated into the workplan of the Scientific Committee. Further, the Scientific Committee recommended that summaries of evidence for changes in stock assessment parameters or processes that could be due to the effects of environmental variability or climate change be developed for all fisheries (SC-CAMLR-42, paragraph 2.149).

In 2024, Members developed such summaries, in the form of tables, for fisheries in Subarea 48.3, Divisions 58.5.1 and 58.5.2 and in the Ross Sea region (Table 8).


Table 8. Table summarising evidence for changes in stock assessment and population parameters or processes that could be due to the effects of environmental variability or climate change in the Patagonian toothfish fishery in Division 58.5.1 (WG-FSA-IMAF-2024/63).
Parameter or process Evidence for trends and potential drivers
Recruitment The assessment model shows decreasing trends of recruitment since 2007 (Massiot-granier et al., 2024a). This trend could be a sign of a regime shift and a change of productivity. Further investigation is needed to confirm this hypothesis and assess the causes of this decrease (fishing; climate change; etc).
Age at maturity (2024 stock assessment values: a50 = 9.25; ato95 = 8.07) Patterns of age at maturity from 2007 to 2023 show no evidence of trends over time (WG-FSA-IMAF-2024/63; Figure 3 and 4). However estimations of a50 for females and males separately indicate that females become mature long after the males. In the stock assessment models maturity is common to males and females. Therefore maturity parameters might change over time due to changes in sex ratio.
Stock-recruit relationship Recruitment is assumed to follow a Beverton-Holt relationship whereby the stock recruitment (SR) is a function of the spawning stock biomass (SSB) the pre-exploitation equilibrium unfished spawning stock biomass (B0) and the parameter steepness h defined as h=SR(0,2B0) and SR=(SSB/B0) / (1-((5h-1)/4h)(1-SSB/B0)). Series of recruitment is too short to analyse potential changes of the stock-recruitment relationship due to climate change. Furthermore comparing recruitment estimates with a recruitment series obtained with surveys (fishery-independent) would help to investigate variations of the stock-recruitment relationship.
Natural mortality Not known.
Growth rates (2024 stock assessment values: k = 0.0662; t0 = -1.12; Linf = 170) Except for years 2013; 2014 and 2015 for which estimated values of t0 are lower there is no temporal trend of growth (WG-FSA-IMAF-2024/63; Figures 7 and 8).
Length-weight Patterns of length-weight relationship show that females tend to have a higher condition (higher weight/length ratio) in the most recent years. This pattern may result from increased sampling of mature females during the reproductive period and will be investigated further. No evidence or variability over time of length-weight relationship is showed for the males (WG-FSA-IMAF-2024/63; Figure 11).
Sex ratio changes Since 2016 inter-annual changes of sex-ratio can be observed with males-biased catches in the most recent years (2020-2022) Figure 12. However the proportion of males in the catch does not exceed 57% during the period 2007-2022 and 54.8% in the last three years.
Spatial distribution Recent analysis of fishing effort data was conducted (Le Clech 2024; Masere et al. 2024). Further investigation is needed to assess if the spatial distribution itself has changed.
Stock structure There is no evidence to suggest that the stock structure for Patagonian toothfish in Kerguelen has changed.
Locations of spawning and site fidelity Ongoing work is conducted to assess spawning locations. Data are too poor to estimate a site fidelity among the years.
Depredation mortality No significant trend has been observed, with the depredation rate fluctuating around 4.5%.


Additional Resources

References

Duhamel, G. and M. Hautecoeur. 2009. Biomass, abundance and distribution of fish in the Kerguelen Islands EEZ (CCAMLR Statistical Division 58.5.1). CCAMLR Science, 16: 1-32.

Duhamel G., P. Pruvost, M. Bertignac, N. Gasco and M. Hautecoeur. 2011. Major fisheries events in the Kerguelen Islands: Notothenia rossii, Champsocephalus gunnari, Dissostichus eleginoides. Current distribution and status of stocks. In: Duhamel, G. and D. Welsford (Eds). The Kerguelen Plateau: marine ecosystem and fisheries. Société française d’ichtyologie, Paris: 275-286.

Duhamel G., Péron C., Sinègre R., Chazeau C., Gasco N., Hautecœur M., Martin A., Durand I., Causse R. Important re-adjustements in the biomass and distribution of groundfish species in the northern part of the Kerguelen Plateau and Skiff bank (2019). CCAMLR Science special issue Kerguelen Plateau Symposium 2017. pp 135-184.

Williams, R., G.N. Tuck, A.J. Constable and T. Lamb. 2002. Movement, growth and available abundance to the fishery of Dissostichus eleginoides Smitt, 1898 at Heard Island, derived from tagging experiments. CCAMLR Science, 9: 33-48.