Fishery Report 2024:
Dissostichus mawsoni in Subarea 48.1
CCAMLR Secretariat
07 April 2025
Antarctic Toothfish, Dissostichus mawsoni Norman, 1937.
Map of the management areas within the CAMLR Convention Area. Subarea 48.1, 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 closed longline fishery for Antarctic toothfish (Dissostichus mawsoni) in Subarea 48.1. This fishery began as a new fishery in 1998, conducted by Chile (Conservation Measure 134/XVI). Following a prospecting longline cruise (SC-CAMLR-XVII/BG/07 Rev. 1) with limited yield, Chile concluded that a new fishery in this area would not be feasible (SC-CAMLR-XVII, paragraph 9.3). Consequently, the Commission prohibited direct fishing (other than for scientific research purposes) for finfish in Subarea 48.1 since 7 November 1998 (CCAMLR-XVII, p. 44; Conservation Measure 72/XVII, then Conservation Measure 32-02).
From 2019 to 2021 Ukraine conducted a research survey in accordance with Conservation Measure 24-01 (SC-CAMLR-XXXVII, paragraphs 3.117-3.122; SC-CAMLR-38, paragraphs 4.24-4.28; SC-CAMLR-40, paragraph 3.97). In 2019 the survey was interrupted due to heavy sea ice conditions, and, in 2020 and 2021 the survey was interrupted because the by-catch limit on Macrourus spp. was reached.
1.2. Conservation Measures currently in force
Directed fishing for Dissostichus spp. in Subarea 48.1 is prohibited under Conservation Measure 32-02 at least until further scientific information is gathered and reviewed by the Scientific Committee and the Working Group on Fish Stock Assessment (WG-FSA).
Figure 1: Location of Research Blocks in Subarea 48.1. The fishable depth range (600m-1800m) is highlighted in shades of green. Coastlines and ice shelves: UK Polar Data Centre/BAS and Natural Earth. Bathymetry: GEBCO. Projection: EPSG 6932 (rotated).
1.3. Active vessels
From 2019 to 2021, 1 Ukrainian-flagged vessel (Calispo) participated in this research survey. No fishing targeting D. mawsoni has taken place in this area since 2021.
1.4. Timeline of spatial management
In 2018, three research blocks (Fig. 1) were proposed by Ukraine in Subarea 48.1 to carry out a longline research survey (WG-FSA-18/20 Rev. 1). Noting the likely lack of accessibility in research block 481_3 due to sea ice, The Scientific Committee recommended that this research proceed in the two other research blocks (SC-CAMLR-XXXVII, paragraph 3.122; SC-CAMLR-38, paragraph 4.26).
2. Reported catch
2.1. Latest reports and limits
Reported catches of D. mawsoni since 2019 in Subarea 48.1 are shown in Table 1. Fishing did not take place in 2022.
| Season | Number of vessels | Catch limit (tonnes) | Catch | Estimated IUU catch (tonnes) |
|---|---|---|---|---|
| 2019 | 1 | 40 | 9 | – |
| 2020 | 1 | 43 | 15 | – |
| 2021 | 1 | 43 | 14 | – |
| 2022 | – | – | – | |
| 2023 | – | – | – | |
| 2024 | – | – | – |
The latest catches of D. mawsoni by research block are indicated in Table 2.
| Research Block | Catch limit | Catch (% of catch limit) |
|---|---|---|
| 481_2 | 43 | 14 (32.6%) |
2.2. By-catch
Catch limits for by-catch species groups (Macrourus spp., skates and rays, and other species) are defined in Conservation Measure 33-03 and shown at the Subarea scale for each fishing season in Table 3.
If the by-catch of any one species is equal to, or greater than, 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 (Conservation Measure 33-03).
Skates thought to have a high probability of survival are released at the surface in accordance with Conservation Measure 33-03.
The by-catch in Subarea 48.1 consists predominantly of Macrourus spp (Table 3). In 2020 and 2021 the survey was concluded prior to reaching the catch limit allocated to D. mawsoni due to the by-catch of Macrourus spp.
| Season | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) | Number Released | Catch Limit (tonnes) | Reported Catch (tonnes) |
|---|---|---|---|---|---|---|---|
| 2019 | 6 | 3 | 2 | <1 | 11 | 6 | <1 |
| 2020 | 7 | 7 | 2 | <1 | 3 | 7 | <1 |
| 2021 | 7 | 7 | 2 | <1 | 6 | 7 | <1 |
| 2022 | – | – | – | – | |||
| 2023 | – | – | – | – | |||
| 2024 | – | – | – | – |
2.3. Vulnerable marine ecosystems (VMEs)
All Members are required to submit, within their general new (Conservation Measure 21-01) and exploratory (Conservation Measure 21-02) 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. For research fisheries notified under Conservation Measure 24-01, exemptions from specific Conservation Measures can be made, as recorded each year under Conservation Measure 24-05. All of the VMEs in CCAMLR’s VME Registry are currently afforded protection through specific area closures.
In 2019, Ukraine indicated that CCAMLR standard methods for the identification of VMEs will be applied on board during the survey (WG-SAM-2019/28).
There are currently 34 VMEs and 3 VME Risk Areas designated in Subarea 48.1.
2.4. Incidental mortality of seabirds and marine mammals
The requirements of Conservation Measure 25-02, including the ‘Minimisation of the incidental mortality of seabirds in the course of longline fishing or longline fishing research in the Convention Area’ apply to this fishery.
The risk level for birds in Subarea 48.1 is category 4 (average to high) (SC-CAMLR-XXX, Annex 8, paragraph 8.1).
There have been no observed seabird mortality reported by vessels in Subarea 48.1 in this research survey.
There have been no observed mammal mortality reported by vessels in Subarea 48.1 in this research survey.
3. Illegal, Unreported and Unregulated (IUU) fishing
IUU fishing activity has not been reported in Subarea 48.1.
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.
Following Conservation Measure 22-07, vessels participating in this fishery must report the occurrence of VME indicator organisms on hauled lines. To do so, the vessel’s crew observe lines in segments (1000-hook sections or 1200m sections, whichever is the shorter) and report the number of VME indicator units (either one litre of those VME indicator organisms that can be placed in a 10-litre container, or one kilogram of those VME indicator organisms that do not fit into a 10-litre container). Depending on the number of VME indicator units landed, vessels must immediately report and potentially cease fishing in the area (termed a Risk Area) until further review of the data is completed (see Conservation Measure 22-07). Based on the portion of the line monitored, observers further identify VME indicator organisms to the lowest taxonomic level possible.
The vessel’s crew report total catch of non-VME by-catch (mostly fishes) 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, as well as data on individual specimens such as size and maturity.
Summaries of data reported to CCAMLR for the past five years are given in Tables 4 and 5.
| Data source | Data class | Variable | 2020 | 2021 | 2022 | 2023 | 2024 |
|---|---|---|---|---|---|---|---|
| Vessel crew | VME | line segments | 72 | 120 | – | – | – |
| VME indicator units > 5 and < 10 | 0 | 0 | – | – | – | ||
| VME indicator units > 10 | 0 | 3 | – | – | – | ||
| by-catch | taxa identified | 9 | 10 | – | – | – | |
| records | 48 | 76 | – | – | – | ||
| Observer | VME | line segments | 72 | 120 | – | – | – |
| taxa identified | 6 | 6 | – | – | – | ||
| weight or volume measurements | 0 | 2 | – | – | – | ||
| toothfish | specimens examined | 554 | 607 | – | – | – | |
| length measurements | 554 | 607 | – | – | – | ||
| weight measurements | 554 | 607 | – | – | – | ||
| sex identifications | 554 | 607 | – | – | – | ||
| maturity stage identifications | 554 | 607 | – | – | – | ||
| gonad weight measurements | 554 | 607 | – | – | – | ||
| otolith samples | 340 | 473 | – | – | – | ||
| by-catch | specimens examined | 736 | 1548 | – | – | – | |
| taxa identified | 12 | 10 | – | – | – | ||
| length measurements | 711 | 1468 | – | – | – | ||
| weight measurements** | 736 | 1548 | – | – | – | ||
| standard length measurements* | 0 | 0 | – | – | – | ||
| wingspan measurements* | 0 | 0 | – | – | – | ||
| pelvic length measurements* | 0 | 0 | – | – | – | ||
| snout to anus measurements* | 418 | 880 | – | – | – | ||
| sex identifications** | 711 | 1469 | – | – | – | ||
| maturity stage identifications** | 711 | 1446 | – | – | – | ||
| gonad weight measurements** | 0 | 13 | – | – | – | ||
| otolith samples** | 160 | 300 | – | – | – | ||
| **: Voluntary records | |||||||
| *: Species-dependent records |
| By-catch group | Variable | 2020 | 2021 | 2022 | 2023 | 2024 |
|---|---|---|---|---|---|---|
| Macrourus spp. | specimens examined | 426 | 880 | – | – | – |
| taxa identified | 2 | 2 | – | – | – | |
| length measurements | 426 | 880 | – | – | – | |
| weight measurements** | 426 | 880 | – | – | – | |
| snout to anus measurements* | 418 | 880 | – | – | – | |
| sex identifications** | 426 | 880 | – | – | – | |
| maturity stage identifications** | 426 | 880 | – | – | – | |
| gonad weight measurements** | 0 | 12 | – | – | – | |
| otolith samples** | 160 | 300 | – | – | – | |
| Other fish | specimens examined | 285 | 589 | – | – | – |
| taxa identified | 8 | 6 | – | – | – | |
| length measurements | 285 | 588 | – | – | – | |
| weight measurements** | 285 | 589 | – | – | – | |
| standard length measurements* | 0 | 0 | – | – | – | |
| sex identifications** | 285 | 589 | – | – | – | |
| maturity stage identifications** | 285 | 566 | – | – | – | |
| gonad weight measurements** | 0 | 1 | – | – | – | |
| otolith samples** | 0 | 0 | – | – | – | |
| **: Voluntary records | ||||||
| *: Species-dependent records |
The counts of by-catch taxa reported above (Table 5) 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.
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).
4.3. Length frequency distributions
The length frequency distributions of the catches of D. mawsoni for 2019-2021 across the entire Subarea and in each Research Block are presented in Figure 4. 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, and the spatial and temporal distributions of fishing.
The majority of D. mawsoni caught in the Subarea 48.1 fishery ranged from 50 to 175 cm in total length (Fig. 4).
Figure 4. Annual length frequency distributions of Dissostichus mawsoni caught in Subarea 48.1 (top panel) and in each Research Block (lower panels). 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 in a given season/area.
4.4. Tagging
Since 2012, vessels have been required to tag and release Dissostichus spp. at a rate of 5 fish per tonne of total catch (Table 6). The tag-overlap statistic estimates the similarity between the size distributions of the fish that are tagged and those that are caught by a vessel. Each vessel catching more than 10 tonnes of each species of Dissostichus is required to achieve a minimum tag-overlap statistic of 60% (Conservation Measure 41-01 Annex C).
| Flag State | Vessel name | 2019 | 2020 | 2021 |
|---|---|---|---|---|
| Ukraine | Calipso | 4.4 (63.1,-) | 5.3 (78.7,NC) | 5.1 (67.9,-) |
To date in this area, 192 D. mawsoni have been tagged and released (1 has been recaptured; Table 7).
| Flag State | Vessel name | 2019 | 2020 | 2021 |
|---|---|---|---|---|
| Ukraine | Calipso | 39 (0) | 79 (1) | 74 (0) |
5. Research
5.1. Status of the science
Catch limits for CCAMLR’s fisheries for D. mawsoni and D. eleginoides for the ‘assessed’ fisheries in Subareas 48.3, 88.1 and 88.2 and Division 58.5.2 are set using fully integrated stock assessments; more basic approaches are used for the ‘data-limited’ fisheries (in Subarea 48.6 and in Area 58 outside the exclusive economic zones (EEZs)). The management of data-limited fisheries has been a major focus of attention in CCAMLR in recent years after the acknowledgement that commercial fishing and routine observer data collection had resulted in too few data to develop a full assessment of the targeted stocks in these areas. CCAMLR has developed a framework for designing and undertaking research fishing designed to lead to an assessment of these toothfish stocks in the short to medium term, established under the provisions of Conservation Measure 41-01. This research planning framework has three phases: a prospecting phase, a biomass estimation phase and an assessment development phase, with a set of decisions and reviews for the progression between stages.
In order to obtain the data necessary for a stock assessment, catch limits for research fishing by commercial vessels are set at a level intended to provide sufficient information (including sufficient recaptures of tagged fish) to achieve a stock assessment within a time period of 3 to 5 years. These catch limits are also set so that they provide reasonable certainty that exploitation rates at the scale of the stock or research unit will not negatively impact the stock. Appropriate exploitation rates are based on estimates from areas with assessed fisheries and are not more than 3-4% of the estimated stock size.
The outcomes of this research survey were presented in WG-SAM-2019/33, WG-SAM-2021/17 and WG-FSA-2021/44, including valuable information on pelagic and benthic ecosystems and underwater footage.
In 2019, WG-FSA-2019/38 presented results of oceanographic research conducted by Ukraine in this area and Subareas 48.2, 88.1 and 88.2.
In 2021, WG-FSA-2021/01 presented results of underwater video observation of benthic fauna including fish, squid and Antarctic krill.
In 2022, WG-FSA-2022/32 presented results of an age determination study focused on Antarctic and Patagonian toothfish and two species of grenadiers. Also, a study led by Chilean scientists and in collaboration with Ukrainian scientists (WG-FSA-2022/18), presented results on an analysis of D. mawsoni trophodynamics including prey composition and fatty acids profile.
5.2. Research plans
5.2.1. Background
Due to a lack of suitable data, robust stock assessment models able to yield advice on catch limits in accordance with CCAMLR decision rules have not yet been developed for a toothfish fishery in Subarea 48.1.
A proposal for this research survey was first presented in WG-SAM-18/11 by Ukraine. Subsequently, following advice from the Scientific Committee and its working groups, the proposal was improved over the years and its updated objectives and results were presented in WG-FSA-2021/44. The Scientific Committee noted (SC-CAMLR-XXXVII, paragraph 3.119) that this initiative could provide important information that would assist in testing population hypotheses developed during the Workshop for the Development of a D. mawsoni Population Hypothesis for Area 48 (WS-DmPH-18).
5.2.2. Objectives
Objective 1: To determine the distribution and abundance of Dissostichus spp. in this part of the subarea 48.1.
Objective 2: To obtain a better understanding of the stock structure of toothfish in the north-western part of the Weddell Sea and adjacent waters.
Objective 3: To collect data on the spatial and depth distributions of the by-catch species to inform the by-catch mitigation measures, and, improve the understanding of the by-catch distribution and trophic relationships and ecosystem function.
Objective 4: To trial monitoring of the hauling process and process of release of tagged fish using video cameras.
5.3. Advice by the Scientific Committee
Research plans for research survey for subarea 48.1 were adopted by the Scientific Committee in 2019 (SC-CAMLR-XXXVII, paragraphs 3.117-3.122). Then in 2020 and 2021 research survey continued (SC-CAMLR-38, paragraphs 4.24-4.28; and SC-CAMLR-40, paragraph 3.97).
6. Stock status
6.1. Summary of current status
As a data-limited fishery, this fishery does not yet have such estimates.
6.2. Assessment method
Stock biomass and catch limits in data-limited fisheries are estimated using the trend analysis. This research survey was conducted as effort-limited and catch limits were set by the Scientific Committee and its working groups.
6.3. Year of last assessment, year of next assessment
The most recent evaluation was in 2021.
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.