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, “2021” refers to the 2020/21 CCAMLR fishing season (from 1 December 2020 to 30 November 2021).

Map of the management areas within the CAMLR Convention Area. The region discussed in this report is shaded in green. Throughout this report, “2021” refers to the 2020/21 CCAMLR fishing season (from 1 December 2020 to 30 November 2021).



1. Introduction to the fishery

1.1. History

This fishery report describes the licensed fishery for Patagonian toothfish (Dissostichus eleginoides) in the area of the Australian Fishing Zone (AFZ) in Division 58.5.2. The area includes the AFZ surrounding Heard Island and McDonald Islands, is located on the Kerguelen Plateau between 50\(^{\circ}\)–56\(^{\circ}\)S and 67\(^{\circ}\)–79\(^{\circ}\)E.

The fishery began in 1997 as a trawl fishery. Longline fishing was introduced in 2003 and both fishing methods continued to be used, with an increasing proportion of longline fishing in each year. Since 2015 almost the entire catch has been taken by longline.

The fishery is managed by the Australian Fisheries Management Authority (AFMA) in accordance with the Conservation Measures adopted by CCAMLR and Australian law. The annual catch limit is based on the management advice from CCAMLR. The current catch limits on the fishery for Dissostichus spp. in Division 58.5.2 are described in Conservation Measure 41-08.


1.2. Conservation Measures currently in force

The limits on the fishery for D. eleginoides in Division 58.5.2 are defined in Conservation Measure 41-08.

Figure 1: Map of the region discussed in this report.

Figure 1: Map of the region discussed in this report.


1.3. Active vessels

In 2021, 5 vessels participated in this fishery.


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 4267 tonnes in 2015. In 2021, 2994 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 IUU estimate available).
Season Longline Catch (tonnes) Trawl Catch (tonnes) Pot Catch (tonnes) Total Catch (tonnes) Number of vessels Catch limit (tonnes) Estimated IUU catch (tonnes)
1997 1808 1808 1 3800 7117
1998 2966 2966 3 3700 4150
1999 3341 3341 2 3690 427
2000 3030 3030 2 3585 1154
2001 2599 2599 2 2995 2004
2002 2514 2514 2 2815 3489
2003 286 2468 2754 3 2879 1274
2004 552 2327 2879 3 2873 531
2005 665 2266 2931 3 2787 265
2006 656 1769 72 2497 3 2584 74
2007 624 1714 2338 2 2427 0
2008 835 1445 2280 3 2500 0
2009 1164 1155 13 2332 3 2500 0
2010 1237 1135 30 2402 3 2550 0
2011 1381 1104 34 2518 3 2550
2012 1369 1302 2671 3 2730
2013 2149 563 41 2753 4 2730
2014 2646 107 2754 4 2730
2015 4062 205 4267 7 4410
2016 2624 158 2783 4 3405
2017 3345 24 3369 4 3405
2018 3083 53 3136 4 3525
2019 3334 68 3402 5 3525
2020 2895 119 3014 5 3030
2021 2891 99 4 2994 5 3030



2.2. By-catch

A number of Conservation Measures, which ensure that impacts on the target and other species are minimised, currently apply to this fishery. Conservation Measure 33-02 specifies that there should be no directed fishing other than for the target species, the by-catch limits for incidentally caught species and the move-on rules if the limits for any one haul are exceeded.

Catch limits for by-catch species groups are defined in Conservation Measure 33-02 and provided in Tables 2 and 3.

A quantitative risk assessment of the Caml grenadier (Macrourus caml) was undertaken in 2015 and WG-FSA-15 recommended a catch limit of 409 tonnes for M. caml and Whitson’s grenadier (M. whitsoni) combined based on the risk assessment in WG-FSA-15/63, and a catch limit of 360 tonnes for bigeye grenadier (M. holotrachys) and ridge-scaled grenadier (M. carinatus) combined based on the previous assessment from 2003. These by catch limits were introduced in 2016 and are reflected in Table 2.


Table 2. Reported catch and catch limits in tonnes for by-catch of Macrourids in this fishery (see Conservation Measure 33-02 for details). Source: fine-scale data.
Macrourus spp.
M. caml and M. whitsoni
M. holotrachys and M. carinatus
Season Catch Limit Longline Catch Trawl Catch Total Catch Catch Limit Longline Catch Trawl Catch Total Catch Catch Limit Longline Catch Trawl Catch Total Catch
1997
1998
<1 <1
1999
<1 <1
2000
4 4
2001
1 1
2002 50 3 3
2003 465 3 1 4
2004 360 42 3 45
2005 360 72 2 74
2006 360 26 <1 27
2007 360 61 5 66
2008 360 81 5 86
2009 360 110 2 112
2010 360 100 3 102
2011 360 147 4 151
2012 360 89 3 92
2013 360 154 3 157
2014 360 175 1 176
2015 360 299 4 303
2016
409 78 1 80 360 220 220
2017
409 89 <1 90 360 235 <1 235
2018
409 100 4 104 360 253 <1 253
2019
409 101 4 105 360 250 <1 250
2020
409 48 <1 48 360 59 59
2021
409 66 <1 67 360 150 <1 150

An analysis of the by-catch species unicorn icefish (Channichthys rhinoceratus) and grey rockcod (Lepidonotothen squamifrons) indicated that both species are widespread over the plateau in depths of <1,000m (WG-FSA-15/50). Up to 2015, the catch limits of C. rhinoceratus and L. squamifrons, 150 tonnes and 80 tonnes respectively, were based on assessments carried out in 1998 (SC-CAMLR-XVII, Annex 5). Catches of each of these species since 2004 have been well below the limits set by CCAMLR (Table 3). A quantitative risk assessment of C. rhinoceratus was undertaken in 2015 and WG-FSA-15 recommended a by-catch limit of 1,663 tonnes for C. rhinoceratus.

Table 3. Reported catch and catch limits in tonnes for by-catch (Skates and rays, C. rhinoceratus, L. squamifrons and other species) in this fishery (see Conservation Measure 33-02 for details). Source: fine-scale data.
Skates and rays
C. rhinoceratus
L. squamifrons
Other species
Season Catch Limit Longline Catch Trawl Catch Total Catch Number Released Catch Limit Longline Catch Trawl Catch Total Catch Catch Limit Longline Catch Trawl Catch Total Catch Catch Limit Longline Catch Trawl Catch Total Catch
1997
2 2 0
0 <1 <1
<1 <1
4 4
1998 120 2 2 0
0 <1 <1
<1 <1
31 31
1999
2 2 0
0
<1 <1
5 5
2000
6 6 0
0 <1 <1
<1 <1
12 12
2001 50 4 4 0
0 <1 <1
3 3
111 111
2002 50 3 3 0
0 1 1
1 1
51 51
2003 120 5 7 13 0
0 <1 <1
<1 <1 <1
9 12 20
2004 120 62 11 73 155 150 0 1 1 80 3 3 50 106 58 164
2005 120 70 3 73 8412 150 0 2 2 80 2 2 50 144 8 152
2006 120 17 12 29 3814 150 0 3 3 80 <1 5 5 50 43 18 61
2007 120 8 10 18 7882 150 0 12 12 80 <1 10 10 50 70 17 86
2008 120 13 8 21 9155 150 0 29 29 80 20 20 50 94 13 107
2009 120 15 9 24 10290 150 0 46 46 80 26 26 50 130 13 143
2010 120 11 6 17 10382 150 0 26 26 80 48 48 50 114 9 123
2011 120 11 3 14 6838 150 0 23 23 80 26 26 50 163 8 171
2012 120 7 3 9 8484 150 0 42 42 80 <1 34 34 50 99 11 110
2013 120 13 11 24 12602 150 0 25 25 80 <1 44 44 50 172 67 239
2014 120 16 <1 16 19565 150 0 <1 <1 80 <1 2 2 50 196 2 198
2015 120 19 5 24 37863 150 0 1 1 80 2 2 50 344 9 353
2016 120 20 1 22 32287 1663 0 9 9 80 <1 3 3 50 331 10 341
2017 120 30 2 31 43848 1663 0 2 2 80 <1 2 2 50 371 17 388
2018 120 21 1 23 31187 1663 0 2 2 80 <1 4 4 50 387 6 393
2019 120 25 <1 25 47657 1663 0 2 2 80 <1 <1 1 50 390 7 397
2020 120 6 <1 6 20769 1663 0 <1 <1 80 <1 4 4 50 121 2 123
2021 120 13 <1 14 28658 1663 0 2 2 80 <1 3 3 50 248 12 260


Length-weight relationships, length-at-maturity data and estimates of abundance from survey data for rajids were presented in WG-FSA-05/70. An analysis of the skate tagging program (WG-FSA-13/22) indicated a recapture rate of <1% and an average distance between release and recapture of 4 nautical miles. An analysis of catch rates from 1997 to 2014 of the three skate species (Nowara et al., 2017) shows a decrease in the average total length of Eaton’s skate (Bathyraja eatonii), but little evidence of depletion on the main trawl grounds. One of the skate species, the Kerguelen sandpaper skate (B. irrasa), shows a slight decline in catch rates in the deeper waters around Heard Island and McDonald Islands where the longline fishery operates. This study also calculated a growth rate of ca. 20mm per year, and a maximum age >20 years for B. eatonii, as estimated from tag returns.

2.3. Vulnerable marine ecosystems (VMEs)

Fishing gear deployed on the seabed can have negative effects on sensitive benthic communities. The potential impacts of fishing gear on the benthic communities in Division 58.5.2 are limited by the small size and number of commercial trawl grounds and the protection of large representative areas of sensitive benthic habitats from direct effects of fishing within the Heard Island and McDonald Islands Marine Reserve, an IUCN Category 1a reserve where fishing is prohibited (SC-CAMLR-XXI/BG/18). The marine reserve covers a total area of 71,000 km2.

By-catch of benthos has been monitored by observers since the early stages of the development of the fishery and the rate of benthos by-catch is generally lower in areas that have subsequently become the main fishing grounds as opposed to locations sampled in the Random Stratified Trawl Survey.

As Conservation Measure 22-06 does not apply to this subarea there are no CCAMLR VMEs or VME Risk Areas designated in Division 58.5.2.


2.4. Incidental mortality of seabirds and marine mammals

Seabird mortality rates during longline operations in this fishery remains low (WG-FSA-2019/31); The three most common species injured or killed in the fishery were Cape petrel (Daption capense), white-chinned petrel (Procellaria aequinoctialis) and grey petrel (P. cinerea) (Table 4).

The level of risk of incidental mortality of birds in Division 58.5.2 is category 4 (average-to-high) (SC-CAMLR-XXX, Annex 8, paragraph 8.1). Longline fishing is conducted in accordance with Conservation Measures 24-02 and 25-02 for the protection of birds so that hook lines sink beyond the reach of birds as soon as possible after being put in the water. Between them, these measures specify the weight requirements for different longline configurations and the use of streamer lines and a bird exclusion device to discourage birds from accessing the bait during setting and hauling. Fishing season and season extensions are specified in Conservation Measure 41-08. If three seabirds are caught during the season extension by a given vessel, fishing during the season extension is to cease immediately for that vessel.

Table 4. Number of reported birds caught (killed or with injuries likely to substantially reduce long-term survival) in this fishery in each fishing season.
Season Daption capense Procellaria aequinoctialis Procellaria cinerea Thalassarche melanophris Other
1998 2
2003 5
2004 2
2005 1
2009 1
2010 2
2012 2
2013 1
2014 1
2015 1
2016 1 2
2017 1
2018 1 1
2019 3
2020 3 1
2021 3 1 1


Mammal mortalities reported in the longline fishery in Division 58.5.2 (Table 5) mainly consist of southern elephant seal (Mirounga leonina).

Low levels of sperm whale depredation have been observed in Division 58.5.2 since 2011 (WG-FSA-15/53). Sperm whale sightings occur exclusively in the April-June period.

Conservation Measure 25-03 is in force to minimise the incidental mortality of birds and mammals during trawl fishing. Measures include developing gear configurations which minimise the chance of birds encountering the net, and the prohibition of discharge of offal and discards during the shooting and hauling of trawl gear.

Table 5. Number of reported mammals killed in this fishery in each fishing season.
Season Arctocephalus gazella Mirounga leonina Otaria byronia Otariidae, Phocidae Phocidae
1998 2
2003 1 3 1
2004 2 1
2005 1 1
2006 1 2
2007 1 1
2008 1 1
2009 2
2012 1
2013 5
2014 1 1
2015 2 2
2016 7 2
2017 4 2
2018 5
2019 3
2020 4
2021 7

3. Illegal, Unreported and Unregulated (IUU) fishing

No illegal, unreported and unregulated (IUU)-listed vessels were sighted in Division 58.5.2 inside the Heard Island and McDonald Islands exclusive economic zone (EEZ) since 2006. However, surveillance reports indicate that IUU fishing activities did occur in Division 58.5.2 outside the Heard Island and McDonald Islands EEZ, and therefore brief fishing forays into the EEZ cannot be discounted. IUU fishing gear was also recovered in 2006 and 2011, indicating IUU fishing activities have potentially occurred in the region. Information from satellite surveillance trials indicated the presence of unidentified vessels in this division outside the Heard Island and McDonald Islands EEZ in 2016. In May 2017, a section of gillnet was recovered during fishing operations in Division 58.5.2. 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. Data are collected during commercial fishing trips and during Random Stratified Trawl Surveys (RSTS). The surveys cover a geographic area over the whole of the plateau shallower than 1,000 m in Division 58.5.2 to determine abundance of D. eleginoides. These surveys have been conducted since 1990 with survey designs described in detail in WG-FSA-06/44 Rev. 1 and in WG-FSA-2021/19 for the 2021 survey.


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 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, 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 6 and 7.

Table 6. 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 2017 2018 2019 2020 2021
Vessel crew by-catch taxa identified 46 62 65 61 100
records 8322 7686 8491 4763 7238
Observer toothfish specimens examined 60683 61569 64564 29149 43151
length measurements 60591 61531 64432 29103 43036
weigth measurements 59613 60726 64371 28856 42861
sex identifications 58790 59942 64564 29149 43151
maturity stage identifications 58764 54200 55991 22200 34878
gonad weight measurements 21 9 33 0 7
otolith samples 6130 6450 6551 3157 4258
by-catch specimens examined 52706 56032 47863 19246 37044
taxa identified 25 22 26 18 27
length measurements 52269 55655 47653 19146 36920
weigth measurements** 52062 46868 47609 19115 36871
standard length measurements* 0 950 3223 3117 7111
wingspan measurements* 10251 9953 13412 2701 5510
pelvic length measurements* 0 0 0 0 0
snout to anus measurements* 31198 35402 31150 13393 24356
sex identifications** 35843 51591 47863 19246 37044
maturity stage identifications** 32119 38948 38255 10209 27833
gonad weight measurements** 0 0 1 0 0
otolith samples** 2045 1777 1300 252 862
**: Voluntary records
*: Species-dependent records
Table 7. 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 2017 2018 2019 2020 2021
Macrourus spp. specimens examined 31409 35550 31195 13425 24399
taxa identified 6 6 6 6 7
length measurements 31073 35260 31055 13340 24301
weigth measurements** 31181 34483 31117 13371 24299
snout to anus measurements* 31197 35402 31149 13393 24354
sex identifications** 20890 35128 31195 13425 24399
maturity stage identifications** 20886 28900 29187 7252 20693
gonad weight measurements** 0 0 1 0 0
otolith samples** 1685 1360 1203 70 752
Skates and rays specimens examined 10319 9984 13436 2703 5521
taxa identified 5 5 4 6 4
length measurements 10226 9902 13372 2690 5499
weigth measurements** 10226 9886 13402 2689 5509
wingspan measurements* 10251 9953 13412 2701 5510
pelvic length measurements* 0 0 0 0 0
sex identifications** 10316 9984 13436 2703 5521
maturity stage identifications** 6597 4481 7769 1495 3327
gonad weight measurements** 0 0 0 0 0
Other fish specimens examined 10978 10498 3232 3118 7124
taxa identified 14 11 16 6 16
length measurements 10970 10493 3226 3116 7120
weigth measurements** 10655 2499 3090 3055 7063
standard length measurements* 0 950 3223 3117 7111
sex identifications** 4637 6479 3232 3118 7124
maturity stage identifications** 4636 5567 1299 1462 3813
gonad weight measurements** 0 0 0 0 0
otolith samples** 360 416 95 182 110
**: Voluntary records
*: Species-dependent records


4.3. Length frequency distributions

Dissostichus eleginoides occurs throughout the Heard Island and McDonald Islands area of the Kerguelen Plateau in Division 58.5.2, from shallow depths near Heard Island to at least 3,000 m depth around the periphery of the plateau. Fish smaller than 60cm total length (TL) are predominantly distributed on the plateau in depths less than 500m, where a small number of areas of persistently high local abundance have been discovered. As fish grow, they move to deeper waters and are recruited to the fishery on the plateau slopes in depths of 450 to 800m where they are vulnerable to trawling. Some areas of high local abundance comprise the main trawling grounds where the majority of fish caught are between 50 and 75cm Total Length. Larger fish are seldom caught by trawling and there is evidence from tag recaptures and size distribution of the catch by depth that fish, as they grow, move into deeper water (>1,000m depth) where they are caught by longline.

The length frequency distributions of D. eleginoides caught by trawl and by longline in Division 58.5.2 are shown in Figures 2 and 3 respectively. Since the start of the fishery >500,000 fish have been measured in this division.


Figure 2. Annual length frequency distributions of *D. eleginoides* caught by trawl 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 2. Annual length frequency distributions of D. eleginoides caught by trawl 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 3. 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 3. 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.


The majority of D. eleginoides caught by trawl measured between 25 and 100cm with a mode around 40-50cm, while those caught by longline measured between 50 and 125cm with a mode around 75cm. The length frequency distribution for the longline fishery includes larger fish because of gear selectivity and because the longline fishery occurs in deeper water where larger toothfish occur. 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.

4.4. Tagging

A tagging study has been undertaken in Division 58.5.2 since the start of the commercial fishery in 1998.

To date, 76712 D. eleginoides have been tagged and released (7114 have been recaptured, 12871 of which were released in this area; Table 8).

Table 8. Recent numbers of Dissostichus eleginoides tagged and recaptured in the area for each fishing Season.
Recaptured
Season Tagged 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Total
1998 1073 72 66 24 10 10 4 2 1 1 2 1 193
1999 757 56 71 19 2 1 1 1 1 1 153
2000 1777 125 101 66 12 8 2 1 1 1 1 318
2001 1599 199 94 48 14 2 1 1 1 1 1 362
2002 1534 255 149 41 12 4 1 2 1 1 466
2003 1576 169 124 24 18 2 6 2 2 3 1 3 1 1 1 357
2004 1562 287 135 25 10 8 7 2 5 2 3 7 2 493
2005 1701 266 88 16 5 9 8 4 3 5 6 11 1 1 1 1 425
2006 2430 220 179 51 26 13 11 12 19 9 11 4 6 1 1 1 2 566
2007 1841 199 120 35 21 13 6 12 10 13 8 3 2 1 1 444
2008 1759 50 61 25 14 9 31 20 25 10 5 5 1 2 1 259
2009 2446 92 101 52 15 28 40 51 14 24 5 9 8 1 440
2010 1769 55 66 14 18 55 37 10 18 14 13 8 1 309
2011 2398 124 150 54 46 46 32 32 32 23 9 6 554
2012 2986 161 124 53 48 40 57 46 28 19 27 603
2013 2003 31 58 100 45 49 52 22 23 11 391
2014 2126 12 87 61 85 46 52 37 23 403
2015 8347 85 273 345 288 251 176 101 1519
2016 5947 49 221 287 265 158 131 1111
2017 6903 56 327 406 328 253 1370
2018 6167 49 438 218 348 1053
2019 6819 107 232 412 751
2020 5106 42 240 282
2021 6086 49 49
Total 76712 12871

Historically, the tagging program had been largely restricted to releases and recaptures of fish caught by trawl on the main trawl ground (WG-FSA-14/43). Tagging data from the main trawl ground were used to estimate natural mortality independently of the CASAL assessment as described in Candy et al. (2011), while the limited spatial extent of the program and mixing of the population to other areas initially restricted the ability to include tagging data as an unbiased index of abundance in the stock assessment. With the start of longlining in 2003, tagging and recapturing of fish has become more widespread. However, the spatial distribution of longline fishing and tagging of fish has been highly variable between years and the level of fish movement and the period of complete mixing is still unknown. Tagging data have been included into the stock assessment since 2014 to inform stock abundance.

5. Research

In each year since 1997, a random stratified trawl survey (RSTS) is conducted to assess the abundance and biology of fish and invertebrate species. The survey provides information for input into the stock assessments for the two target species in this area, D. eleginoides and C. gunnari. Surveys have been conducted as consistently as possible each year to ensure a continuous time series of data from the fishery. The random stratified trawl surveys have two long-term aims:

  • to assess the abundance of juvenile and adult D. eleginoides on the shallow and deep parts of the Heard Island Plateau (300 to 1000m); and

  • to assess the abundance of C. gunnari on the Heard Island Plateau.

In 2021, the catch of Patagonian toothfish (Dissostichus eleginoides) was 77.9 t - the second highest catch since the RSTS began and the catch of mackerel icefish (Champsocephalus gunnari) was 35.7 t which represents an almost 5-fold increase in catch from 2020 (WG-FSA-2021/19). Biomass estimates for the managed by-catch species unicorn icefish (Champsocephalus rhinoceratus) showed a steady increase in catch whereas grey rockcod (Lepidonotothen squamifrons) was relatively similar to last year and the catch of Macrourus spp. has declined. All three species of skate were caught in lower numbers than has been the case in recent years (WG-FSA-2021/19).

In 2019, catch removals due to killer and sperm whale interactions across subantarctic fisheries were estimated (WG-FSA-2019/33).

6. Stock status

6.1. Summary of current status

The 2021 assessment model (see Stock Assessment Report) led to a slightly smaller estimate of the virgin spawning stock biomass B0 than that obtained in 2019, with an MCMC estimate of 69,210 tonnes (95% CI: 64,811-74,758 tonnes). The estimated SSB status at the end of 2021 was 0.45 (95% CI: 0.44-0.47), in line with the projection from the 2019 stock assessment.


6.2. Assessment method

The assessment model in 2021 was a single-sex, single-area, age-structured CASAL integrated stock assessment model (see Stock Assessment Report).


6.3. Year of last assessment, year of next assessment

Assessments are reviewed biennially, the last assessment was in 2021.


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.

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.


Additional Resources

References

Candy, S.G., D.C. Welsford, T. Lamb, J.J. Verdouw and J.J. Hutchins. 2011. Estimation of natural mortality for the Patagonian toothfish at Heard and McDonald Islands using catch-at-age and aged mark-recapture data from the main trawl ground. CCAMLR Science, 18: 29-45.

Francis, R.I.C.C. 2011a. Data weighting in statistical fisheries stock assessment models. Can. J. Fish. Aquat. Sci., 68: 1124-1138.

Francis, R.I.C.C. 2011b. Corrigendum: Data weighting in statistical fisheries stock assessment models. Can. J. Fish. Aquat. Sci., 68: 2228.

Nowara, G.B., P. Burch, N. Gasco, D.C. Welsford, T.D. Lamb, C. Chazeau, G. Duhamel, P. Pruvost, S. Wotherspoon and S. Candy. 2017. Distribution and abundance of skates (Bathyraja spp.) on the Kerguelen Plateau through the lens of the toothfish fisheries. Fish. Res., 186: 65-81.