Antarctic toothfish, *Dissostichus mawsoni* Norman, 1937, and, Patagonian Toothfish, *Dissostichus eleginoides* Smitt, 1898.

Antarctic toothfish, Dissostichus mawsoni Norman, 1937, and, Patagonian Toothfish, Dissostichus eleginoides Smitt, 1898.


Map of the management areas within the CAMLR Convention Area. Subarea 48.4, the region discussed in this report is shaded in green. Throughout this report, “2022” refers to the 2021/22 CCAMLR fishing season (from 1 December 2021 to 30 November 2022).

Map of the management areas within the CAMLR Convention Area. Subarea 48.4, the region discussed in this report is shaded in green. Throughout this report, “2022” refers to the 2021/22 CCAMLR fishing season (from 1 December 2021 to 30 November 2022).



1. Introduction to the fishery

1.1. History

This report describes the longline fishery for Patagonian (Dissostichus eleginoides) and Antarctic (D. mawsoni) toothfish in Subarea 48.4.

The fishery for D. eleginoides in Subarea 48.4 was initiated as a new fishery in 1993 following notifications from Chile and the USA (SC-CAMLR-XI, Annex 5, paragraph 6.22), and the adoption of Conservation Measure 44/XI, which set a precautionary catch limit for D. eleginoides of 240 tonnes for that season. Subsequently, the USA withdrew from the fishery and the Chilean longline vessel abandoned fishing after one week of poor catches (SC-CAMLR-XII, Annex 5, paragraph 6.2). In addition, a Bulgarian-flagged longliner fished in November and December 1992 and reported a catch of 39 tonnes of D. eleginoides (SC-CAMLR-XII, Annex 5, paragraph 6.1).

There was no further fishing activity in Subarea 48.4 until 2005 when a mark-recapture experiment was initiated.


1.2. Conservation Measures currently in force

The limits on the established fishery for Dissostichus spp. in Subarea 48.4 are defined in Conservation Measure 41-03.

Figure 1: Location of the area of directed fishing in Subarea 48.4.

Figure 1: Location of the area of directed fishing in Subarea 48.4.


1.3. Active vessels

In 2022, 1 vessel participated in this fishery.


1.4. Timeline of spatial management

In 2008, the Commission agreed to divide Subarea 48.4 into a northern area (Subarea 48.4N) and a southern area (Subarea 48.4S) with directed longline fisheries of D. eleginoides in Subarea 48.4N and Dissostichus spp. in Subarea 48.4S with a single catch limit applied to both species.

In 2014, the management approach in this Subarea was changed and rather than using the northern and southern areas, separate catch limits were set for each species within the directed fishing area specified in Conservation Measure 41-03 (see Fig. 1).


2. Reported catch

2.1. Latest reports and limits

Reported catches of Dissostichus spp. are presented in Table 1. In this fishery, the catch of D. eleginoides reached a maximum of 98 tonnes in 2008. In 2022, 14 tonnes of D. eleginoides and 32 tonnes of D. mawsoni were caught.


Table 1. Catch (tonnes) and effort history in for Dissostichus spp. in this fishery. The separate catch limits for D. eleginoides and D. mawsoni from 2014 onwards are shown here separated by a semicolon (-: no IUU estimate available). Source: Fine scale data.
Season Number of vessels Catch limit (tonnes) D. eleginoides D. mawsoni Estimated IUU catch (tonnes)
1990 1 0 0 –
1992 1 27 0 –
1993 1 12 0 –
2005 1 100 27 0 –
2006 2 100 19 0 –
2007 2 100 54 0 –
2008 2 100 98 0 –
2009 2 150 74 59 –
2010 2 116 57 56 –
2011 2 70 39 15 –
2012 2 81 55 22 –
2013 2 115 72 40 –
2014 2 44 ; 24 44 24 –
2015 2 42 ; 28 42 28 –
2016 2 47 ; 39 42 28 –
2017 2 47 ; 38 28 19 –
2018 2 26 ; 37 17 32 –
2019 2 26 ; 37 17 33 –
2020 2 27 ; 45 19 44 –
2021 2 27 ; 45 16 43 –
2022 1 23 ; 50 14 32 –


2.2. By-catch

Catch limits for by-catch species groups (Macrourus spp., skates and rays, and other species) are defined in Conservation Measure 41-03.

As defined in Conservation Measure 41-03, if the by-catch of skates exceeded 5% of the catch of Dissostichus spp. in any one haul or set, or if the catch of Macrourus spp. reached 150kg and exceeds 16% of the catch of Dissostichus spp. 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.

In addition to the mitigation measures described in Conservation Measure 41-03, skates are handled and released following ‘Year-of-the-Skate’ protocols to maximise their survival.

Catches of by-catch species groups (Macrourus spp., skates and rays, and other species) and number of skates released alive, are summarised in Table 2. The by-catch limits in Subarea 48.4 (as set out in Conservation Measure 41-03) have changed with the development of the fishery research: prior to 2009 there were no specified limits, from 2009 to 2013 there was an overall by-catch limit for macrourids and skates in area 48.4N and a move-on rule provision in Subarea 48.4S, and in 2014, with the introduction of species-specific catch limits for the two target species, whole-fishery catch limits for macrourids and skates were introduced.


Table 2. Reported catch and catch limits for by-catch species (Macrourus spp., skates and rays, and others) in this fishery (see Conservation Measure 41-03 for details). Source: fine-scale data.
Macrourus spp.
Skates and rays
Other catch
Season Catch Limit (tonnes) Reported Catch (tonnes) Catch Limit (tonnes) Reported Catch (tonnes) Number Released Catch Limit (tonnes) Reported Catch (tonnes)
1990 <1 <1 0 <1
1992 0 0 0 0
1993 0 0 0 0
2005 3 0 0 <1
2006 5 1 4359 <1
2007 14 2 6515 <1
2008 16 4 8276 <1
2009 26 2 9767 1
2010 16 2 6183 1
2011 5 <1 4680 <1
2012 7 <1 5582 <1
2013 6 <1 3115 <1
2014 11 3 3.5 <1 1124 <1
2015 11.2 4 3.5 <1 624 <1
2016 13.8 3 4.3 <1 1203 <1
2017 13.6 4 4.3 <1 1549 <1
2018 10.1 5 3.2 2 1768 <1
2019 10.1 4 3.2 <1 1750 <1
2020 11.5 3 3.6 <1 2322 <1
2021 11.5 8 3.6 <1 2016 <1
2022 12 10 4 <1 3784 <1

The distribution of skates and macrourids in Subarea 48.4 has been investigated and their distributions described in WG-FSA-09/17 and WG-FSA-09/18.

Catch rates for macrourids in the north of Subarea 48.4 were high at the start of the fishery. Vessels subsequently altered their fishing techniques and areas to avoid macrourid by-catch and rates dropped (Table 2).

Macrourid catches were previously thought to be almost entirely comprised of Whitson’s grenadier (Macrourus whitsoni). Subsequent taxonomic studies (including genetic analyses) now indicate that the Macrourid population comprises two species, including M. whitsoni and the recently described species Caml grenadier (M. caml) (WG-FSA-10/33; McMillan et al., 2012).


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 48.4. There are fishery-specific restrictions in place to mitigate the impact of the fishery on VMEs, including benthic communities and benthos such as seamount and hydrothermal vent communities and cold-water corals.

2.4. Incidental mortality of seabirds and marine mammals

In 2017 one Southern giant petrel (Macronectes giganteus), and in 2022 one grey-headed albatross (Thalassarche chrysostoma) were killed in this fishery. There have been no reported mammal mortalities reported by vessels in this fishery.

The level of risk of incidental mortality of birds in Subarea 48.4 is category 3 (medium) (SC-CAMLR-XXX, Annex 8, paragraph 8.1).

Conservation Measure 25-02 on minimisation of the incidental mortality of birds in longline fishing applies to this Subarea. Conservation Measure 41-03 also stipulates that if any vessel catches three seabirds in a season then that vessel must only set longlines at night.


3. Illegal, Unreported and Unregulated (IUU) fishing

Data on potential illegal, unreported and unregulated (IUU) fishing in this Subarea is limited to sightings from licenced vessels (including fishing vessels, expedition yachts and research ships). There has been no recorded evidence of IUU fishing activities in Subarea 48.4 since 2006.


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 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.

Conservation Measures 22-06 and 22-07 do not apply to this fishery.

Summaries of data reported to CCAMLR for the past five years are given in Tables 3 and 4.

Table 3. Summary of by-catch and biological data reported by vessels crew and observers in each of the last five seasons. By-catch records correspond to the number of observations of total weight and count of individuals for each taxon identified. Observers may take further biological measurements on toothfish and by-catch taxa. Taxonomic identification may occur at different levels.
Data source Data class Variable 2018 2019 2020 2021 2022
Vessel crew by-catch taxa identified 12 7 5 9 7
records 273 225 183 242 273
Observer toothfish specimens examined 1346 1270 1050 910 1186
length measurements 1346 1268 1050 910 1186
weight measurements 1345 1265 1047 819 751
sex identifications 1346 1270 1048 829 769
maturity stage identifications 1342 1259 1044 825 768
gonad weight measurements 1340 1256 1035 823 678
otolith samples 739 758 622 465 365
by-catch specimens examined 833 917 517 351 621
taxa identified 8 6 8 8 9
length measurements 833 915 212 351 620
weight measurements** 831 912 515 348 613
standard length measurements* 0 0 27 0 0
wingspan measurements* 142 95 31 63 31
pelvic length measurements* 142 95 31 64 31
snout to anus measurements* 474 591 424 157 387
sex identifications** 815 917 334 347 30
maturity stage identifications** 789 916 299 342 26
gonad weight measurements** 246 1 0 197 0
otolith samples** 2 0 223 0 0
**: Voluntary records
*: Species-dependent records
Table 4. 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.
By-catch group Variable 2018 2019 2020 2021 2022
Macrourus spp. specimens examined 474 591 414 157 387
taxa identified 3 2 2 3 3
length measurements 474 590 119 157 387
weight measurements** 474 591 412 157 387
snout to anus measurements* 474 591 414 157 387
sex identifications** 464 591 252 157 0
maturity stage identifications** 462 591 232 153 0
gonad weight measurements** 146 0 0 107 0
otolith samples** 0 0 207 0 0
Skates and rays specimens examined 142 95 31 64 31
taxa identified 1 1 1 1 1
length measurements 142 95 31 64 30
weight measurements** 142 90 31 61 23
wingspan measurements* 142 95 31 63 31
pelvic length measurements* 142 95 31 64 31
sex identifications** 135 95 31 62 30
maturity stage identifications** 112 94 31 63 26
gonad weight measurements** 0 1 0 19 0
Other fish specimens examined 217 231 72 130 203
taxa identified 4 3 5 4 5
length measurements 217 230 62 130 203
weight measurements** 215 231 72 130 203
standard length measurements* 0 0 27 0 0
sex identifications** 216 231 51 128 0
maturity stage identifications** 215 231 36 126 0
gonad weight measurements** 100 0 0 71 0
otolith samples** 0 0 16 0 0
**: Voluntary records
*: Species-dependent records


The counts of by-catch taxa reported above (Table 4) 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 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.

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.



4.3. Length frequency distributions

The recent length frequency distributions of D. eleginoides and D. mawsoni caught in this fishery are presented in Figures 4 and 5. 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.

The length frequency distribution of D. eleginoides caught in Subarea 48.4 shows a shifting mode from around 120 cm at the beginning of the time series to 140 cm in recent years (Figure 4). A second mode of smaller fish (75cm) is evident in 2013 and develops throughout the remainder of the time series, indicating a recruitment pulse.

The length frequency distribution of D. mawsoni (Figure 5) is dominated by a single strong mode around 150cm and does not show any cohort progression between years as observed in the length frequency distributions of D. eleginoides.


Figure 4. Annual length frequency distributions of *D. eleginoides* caught in Subarea 48.4. 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.

Figure 4. Annual length frequency distributions of D. eleginoides caught in Subarea 48.4. 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.

Figure 5. Annual length frequency distributions of *Dissostichus mawsoni* caught in Subarea 48.4. 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.

Figure 5. Annual length frequency distributions of Dissostichus mawsoni caught in Subarea 48.4. 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.


4.4. Tagging

In 2005, the UK conducted a pilot tagging program using a longline fishing vessel. Following the pilot study, the Commission agreed to continue the tagging experiment in Subarea 48.4.

Since 2012, vessels have been required to tag and release Dissostichus spp. at a minimum rate of 5 fish per tonne of green weight caught. All vessels which have fished in Subarea 48.4 have exceeded the minimum required tagging rate. Tagging data now underpin stock assessments for Subarea 48.4.

The tag-overlap statistic estimates the similarity between the size distributions of those fish that are tagged by a vessel and of all the fish that are caught by that vessel. In exploratory fisheries since 2015, each vessel releasing more than 30 tagged fish of each species of Dissostichus is required to achieve a minimum tag-overlap statistic of 60% (Annex 41-01/C). Vessels fishing in Subarea 48.4 have exceeded this requirement.

To date in this area, 2790 D. mawsoni have been tagged and released (181 have been recaptured, 164 of which were released in this area; Table 5), and, 4226 D. eleginoides have been tagged and released (567 have been recaptured, 535 of which were released in this area; Table 6).

One tagged D. eleginoides has also moved into Subarea 48.4 from Subarea 48.3 (WG-FSA-14/29 Rev. 1; WG-FSA-17/06). One D. mawsoni tagged in Subarea 48.4 was reported recaptured in Subarea 88.2 after three years at liberty. During the survey in the south of Subarea 48.4, 85 D. mawsoni were tagged and none recaptured.

WG-FSA-09/17, WG-FSA-09/18 and WG-FSA-16/40 Rev. 1 provided a comprehensive analysis of the catch distribution of the two Dissostichus species in Subarea 48.4.

Table 5. Number of Dissostichus mawsoni tagged and recaptured in the area for each fishing season.
Recaptured
Season Tagged 2009 2010 2011 2012 2014 2015 2016 2017 2018 2019 2020 2021 2022 Total
2006 10
2007 1
2009 193 2 15 3 2 22
2010 202 6 4 1 11
2011 83 1 1 2
2012 147
2013 179 1 1 1 2 5
2014 191 13 1 1 1 16
2015 584 12 5 1 1 19
2016 149 8 5 2 1 1 17
2017 104 3 3 1 7
2018 161 3 1 1 1 6
2019 168 2 6 3 11
2020 229 16 3 19
2021 224 12 15 27
2022 165 2 2
Total 2790 164


Table 6. 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 Total
2005 42 2 2 1 1 6
2006 134 2 8 5 2 1 1 2 2 1 24
2007 291 13 12 1 4 5 4 2 1 2 2 46
2008 504 8 11 7 11 10 4 3 6 6 2 3 2 1 74
2009 558 3 16 12 11 8 2 5 3 3 1 4 1 69
2010 418 2 12 2 12 4 1 4 2 2 2 3 1 47
2011 222 2 3 4 2 1 1 1 1 15
2012 302 7 3 2 2 2 5 3 1 1 26
2013 470 23 19 15 7 1 4 3 2 4 78
2014 223 20 12 9 1 2 2 1 2 49
2015 226 11 12 7 4 1 5 2 42
2016 225 5 1 4 3 9 5 27
2017 159 1 1 1 2 5 1 11
2018 87 1 3 2 6
2019 91 3 3 1 7
2020 102 3 3
2021 97 5 5
2022 75
Total 4226 535


5. Research

A precautionary approach has been applied in treating the Subarea 48.4 D. mawsoni as a separate stock. Based on the biological characteristics of the catches in Subarea 48.4, and the surrounding regions, the D. mawsoni around the southern South Sandwich Islands are now hypothesised as being part of a much larger stock that extends south into Subarea 48.2, 48.6 and possibly 48.5 (WG-FSA-2019/27).

According to the Stock Assessment of D. eleginoides in this fishery, observed recruitment is characterised by a large pulse from the early 2000s, followed by low background levels of recruitment. The stock hypothesis currently used in the assessment assumes a single stock unit for this subarea. The characteristics of the growth and maturity do not provide evidence for localised spawning activity.

The UK conducted a multi-year (2017-2019) effort-limited research program to the south of the directed fishery area in Subarea 48.4 examining the linkages between D. mawsoni in Subarea 48.2 and the adjacent area of Subarea 48.4. The results provided evidence linking D. mawsoni with the Antarctic continental shelf and a potential spawning region in Subarea 48.2 (WG-FSA-2021/22). The movements of tagged fish indicated potential connections with the Lazarev Sea (Subarea 48.6) as well as the southern South Sandwich Islands (WG-FSA-2021/22).

6. Stock status

6.1. Summary of current status

A CASAL based assessment of D. eleginoides indicated that the stock was at 65% of B0 in 2021 (see Stock Assessment Report).

The five-year (2018-2022) average biomass of D. mawsoni in this Subarea, estimated from mark-recapture data was 1110 tonnes (see Stock Assessment Report).


6.2. Assessment method

The stock of D. eleginoides in this Subarea is assessed using a combined-sex, single-area integrated CASAL stock assessment (see Stock Assessment Report).

The stock of D. mawsoni in this Subarea is assessed using a tag-recapture based population assessment (see Stock Assessment Report).


6.4. Year of last assessment, year of next assessment

Assessments are reviewed biennially, the last assessments were in 2021.


7. Climate Change and environmental variability

In 2018, a summary of the potential impacts of climate change on Southern Ocean fisheries (FAO 2018) highlighted 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.

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 also welcomed (CCAMLR-41, paragraph 6.8) the Scientific Committee’s agreement to hold a workshop on climate change in the first half of 2023 (SC-CAMLR-41, paragraph 7.10) and encouraged the inclusion of a range of scientific experts as well as policy makers to foster integration of the best available science into management actions. The Commission adopted (CCAMLR-41, paragraph 6.28) Resolution 36/41.


References

McMillan, P., T. Iwamoto, A. Stewart and P.J. Smith. 2012. A new species of grenadier, genus Macrourus (Teleostei, Gadiformes, Macrouridae) from the southern hemisphere and a revision of the genus. Zootaxa, 3165: 1-24.

Additional Resources