Fishery Report 2022:
Dissostichus eleginoides at Heard Island (Division 58.5.2)
CCAMLR Secretariat
17 March 2023
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, “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 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, and 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 2013 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.
1.3. Active vessels
In 2022, 4 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 2022, 2766 tonnes of D. eleginoides were caught.
| 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 | 2995 | 5 | 3030 | – |
| 2022 | 2698 | 68 | – | 2766 | 4 | 3010 | – |
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, with by-catch limits and move-on rules if the by-catch 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.
| 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 | – | 0 | 0 | – | – | – | – | – | 0 | |||
| 1998 | – | <1 | <1 | – | – | – | – | – | 0 | |||
| 1999 | – | <1 | <1 | – | – | – | – | – | 0 | |||
| 2000 | – | 4 | 4 | – | – | – | – | – | 0 | |||
| 2001 | – | 1 | 1 | – | – | – | – | – | 0 | |||
| 2002 | 50 | – | 3 | 3 | – | – | – | – | – | 0 | ||
| 2003 | 465 | 3 | 1 | 4 | – | – | – | – | – | 0 | ||
| 2004 | 360 | 42 | 3 | 45 | – | – | – | – | – | 0 | ||
| 2005 | 360 | 72 | 2 | 74 | – | – | – | – | – | 0 | ||
| 2006 | 360 | 26 | <1 | 27 | – | – | – | – | – | 0 | ||
| 2007 | 360 | 61 | 5 | 66 | – | – | – | – | – | 0 | ||
| 2008 | 360 | 81 | 5 | 86 | – | – | – | – | – | 0 | ||
| 2009 | 360 | 110 | 2 | 112 | – | – | – | – | – | 0 | ||
| 2010 | 360 | 100 | 3 | 102 | – | – | – | – | – | 0 | ||
| 2011 | 360 | 147 | 4 | 151 | – | – | – | – | – | 0 | ||
| 2012 | 360 | 89 | 3 | 92 | – | – | – | – | – | 0 | ||
| 2013 | 360 | 154 | 3 | 157 | – | – | – | – | – | 0 | ||
| 2014 | 360 | 175 | 1 | 176 | – | – | – | – | – | 0 | ||
| 2015 | 360 | 299 | 4 | 303 | – | – | – | – | – | 0 | ||
| 2016 | – | – | – | 409 | 78 | 1 | 80 | 360 | 220 | 0 | 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 | 0 | 59 | |
| 2021 | – | – | – | 409 | 66 | <1 | 67 | 360 | 150 | <1 | 150 | |
| 2022 | – | – | – | 409 | 45 | <1 | 46 | 360 | 113 | <1 | 113 |
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.
| 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 | – | <1 | <1 | – | <1 | <1 | – | 4 | 4 | ||||
| 1998 | 120 | – | 2 | 2 | 0 | – | <1 | <1 | – | <1 | <1 | – | 31 | 31 | |||
| 1999 | – | 2 | 2 | 0 | – | 0 | 0 | – | <1 | <1 | – | 5 | 5 | ||||
| 2000 | – | 6 | 6 | 0 | – | <1 | <1 | – | <1 | <1 | – | 12 | 12 | ||||
| 2001 | 50 | – | 4 | 4 | 0 | – | <1 | <1 | – | 3 | 3 | – | 111 | 111 | |||
| 2002 | 50 | – | 3 | 3 | 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 | 0 | 3 | 3 | 50 | 106 | 58 | 164 |
| 2005 | 120 | 70 | 3 | 73 | 8412 | 150 | 0 | 2 | 2 | 80 | 0 | 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 | 0 | 20 | 20 | 50 | 94 | 13 | 107 |
| 2009 | 120 | 15 | 9 | 24 | 10290 | 150 | 0 | 46 | 46 | 80 | 0 | 26 | 26 | 50 | 130 | 13 | 143 |
| 2010 | 120 | 11 | 6 | 17 | 10382 | 150 | 0 | 26 | 26 | 80 | 0 | 48 | 48 | 50 | 114 | 9 | 123 |
| 2011 | 120 | 11 | 3 | 14 | 6838 | 150 | 0 | 23 | 23 | 80 | 0 | 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 | 0 | 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 |
| 2022 | 120 | 27 | <1 | 27 | 30003 | 1663 | 0 | <1 | <1 | 80 | <1 | 3 | 3 | 50 | 210 | <1 | 211 |
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), showed 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 km\(^2\).
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 area there are no CCAMLR VMEs or VME Risk Areas designated in Division 58.5.2.
2.4. Incidental mortality of seabirds and marine mammals
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.
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).
| 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 | ||
| 2022 | 3 |
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.
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.
| 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 | ||||
| 2022 | 13 |
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-2022/07 for the 2022 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.
| Data source | Data class | Variable | 2018 | 2019 | 2020 | 2021 | 2022 |
|---|---|---|---|---|---|---|---|
| Vessel crew | by-catch | taxa identified | 62 | 65 | 61 | 100 | 85 |
| records | 7686 | 8491 | 4763 | 7238 | 7114 | ||
| Observer | toothfish | specimens examined | 61569 | 64564 | 29149 | 43151 | 49811 |
| length measurements | 61531 | 64432 | 29103 | 43036 | 49513 | ||
| weight measurements | 60726 | 64371 | 28856 | 42861 | 49448 | ||
| sex identifications | 59942 | 64564 | 29149 | 43151 | 49811 | ||
| maturity stage identifications | 54200 | 55991 | 22200 | 34878 | 43323 | ||
| gonad weight measurements | 9 | 33 | 0 | 7 | 4486 | ||
| otolith samples | 6450 | 6551 | 3157 | 4258 | 5813 | ||
| by-catch | specimens examined | 56032 | 47863 | 19246 | 37044 | 38707 | |
| taxa identified | 22 | 26 | 18 | 27 | 57 | ||
| length measurements | 55655 | 47653 | 19146 | 36920 | 38542 | ||
| weight measurements** | 46868 | 47609 | 19115 | 36871 | 38600 | ||
| standard length measurements* | 950 | 3223 | 3117 | 7111 | 3715 | ||
| wingspan measurements* | 9953 | 13412 | 2701 | 5510 | 10052 | ||
| pelvic length measurements* | 0 | 0 | 0 | 0 | 0 | ||
| snout to anus measurements* | 35402 | 31150 | 13393 | 24356 | 24794 | ||
| sex identifications** | 51591 | 47863 | 19246 | 37044 | 38707 | ||
| maturity stage identifications** | 38948 | 38255 | 10209 | 27833 | 28173 | ||
| gonad weight measurements** | 0 | 1 | 0 | 0 | 7 | ||
| otolith samples** | 1777 | 1300 | 252 | 862 | 588 | ||
| **: Voluntary records | |||||||
| *: Species-dependent records |
| By-catch group | Variable | 2018 | 2019 | 2020 | 2021 | 2022 |
|---|---|---|---|---|---|---|
| Macrourus spp. | specimens examined | 35550 | 31195 | 13425 | 24399 | 24818 |
| taxa identified | 6 | 6 | 6 | 7 | 6 | |
| length measurements | 35260 | 31055 | 13340 | 24301 | 24700 | |
| weight measurements** | 34483 | 31117 | 13371 | 24299 | 24770 | |
| snout to anus measurements* | 35402 | 31149 | 13393 | 24354 | 24771 | |
| sex identifications** | 35128 | 31195 | 13425 | 24399 | 24818 | |
| maturity stage identifications** | 28900 | 29187 | 7252 | 20693 | 20179 | |
| gonad weight measurements** | 0 | 1 | 0 | 0 | 0 | |
| otolith samples** | 1360 | 1203 | 70 | 752 | 353 | |
| Skates and rays | specimens examined | 9984 | 13436 | 2703 | 5521 | 10080 |
| taxa identified | 5 | 4 | 6 | 4 | 5 | |
| length measurements | 9902 | 13372 | 2690 | 5499 | 10040 | |
| weight measurements** | 9886 | 13402 | 2689 | 5509 | 10036 | |
| wingspan measurements* | 9953 | 13412 | 2701 | 5510 | 10052 | |
| pelvic length measurements* | 0 | 0 | 0 | 0 | 0 | |
| sex identifications** | 9984 | 13436 | 2703 | 5521 | 10080 | |
| maturity stage identifications** | 4481 | 7769 | 1495 | 3327 | 6200 | |
| gonad weight measurements** | 0 | 0 | 0 | 0 | 0 | |
| Other fish | specimens examined | 10498 | 3232 | 3118 | 7124 | 3809 |
| taxa identified | 11 | 16 | 6 | 16 | 46 | |
| length measurements | 10493 | 3226 | 3116 | 7120 | 3802 | |
| weight measurements** | 2499 | 3090 | 3055 | 7063 | 3794 | |
| standard length measurements* | 950 | 3223 | 3117 | 7111 | 3715 | |
| sex identifications** | 6479 | 3232 | 3118 | 7124 | 3809 | |
| maturity stage identifications** | 5567 | 1299 | 1462 | 3813 | 1794 | |
| gonad weight measurements** | 0 | 0 | 0 | 0 | 7 | |
| otolith samples** | 416 | 95 | 182 | 110 | 235 | |
| **: Voluntary records | ||||||
| *: Species-dependent records |
The counts of by-catch taxa reported above (Table 7) 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.
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 4 and 5 respectively. Since the start of the fishery >500,000 fish have been measured in this division.
Figure 4. 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 5. 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, 82054 D. eleginoides have been tagged and released (14436 have been recaptured; Table 8).
| 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 | 2022 | 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 | 1 | 567 | ||||||||
| 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 | 100 | 52 | 15 | 28 | 40 | 51 | 14 | 24 | 5 | 9 | 8 | 1 | 1 | 440 | |||||||||||
| 2010 | 1769 | 55 | 66 | 14 | 18 | 55 | 37 | 10 | 18 | 13 | 13 | 8 | 1 | 2 | 310 | ||||||||||||
| 2011 | 2398 | 124 | 150 | 54 | 46 | 46 | 32 | 32 | 32 | 23 | 9 | 6 | 3 | 557 | |||||||||||||
| 2012 | 2986 | 161 | 124 | 53 | 48 | 40 | 57 | 46 | 28 | 19 | 27 | 5 | 608 | ||||||||||||||
| 2013 | 2003 | 31 | 58 | 99 | 45 | 49 | 52 | 22 | 23 | 11 | 9 | 399 | |||||||||||||||
| 2014 | 2126 | 12 | 87 | 61 | 84 | 46 | 52 | 37 | 23 | 8 | 410 | ||||||||||||||||
| 2015 | 8347 | 85 | 273 | 345 | 287 | 251 | 176 | 101 | 71 | 1589 | |||||||||||||||||
| 2016 | 5947 | 49 | 221 | 287 | 265 | 158 | 131 | 77 | 1188 | ||||||||||||||||||
| 2017 | 6903 | 56 | 332 | 406 | 328 | 253 | 173 | 1548 | |||||||||||||||||||
| 2018 | 6167 | 51 | 438 | 218 | 348 | 180 | 1235 | ||||||||||||||||||||
| 2019 | 6819 | 107 | 232 | 412 | 331 | 1082 | |||||||||||||||||||||
| 2020 | 5106 | 42 | 240 | 244 | 526 | ||||||||||||||||||||||
| 2021 | 6086 | 49 | 393 | 442 | |||||||||||||||||||||||
| 2022 | 5342 | 65 | 65 | ||||||||||||||||||||||||
| Total | 82054 | 14436 |
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 (300m 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 2022, a new set of randomly selected haul stations were included in the RSTS (WG-FSA-2022/07). The catch of Patagonian toothfish (Dissostichus eleginoides) was 36.2 t. The catch of mackerel icefish (Champsocephalus gunnari) was 71 t. which is the largest catch in the history of the survey. Biomass estimates for most of the managed by-catch species were similar to the survey averages in recent years whilst the biomass of Bathyraja murrayi has declined.
In 2019, catch removals due to killer and sperm whale interactions across subantarctic fisheries were estimated (WG-FSA-2019/33).
In 2022, WG-FSA-2022/09 presented an update on stock parameters, including recruitment indices from the random stratified trawl survey, and Chapman estimates of vulnerable biomass from tag-recapture data. These data indicated that the stock trajectory was consistent with that predicted by the 2021 stock assessment model. Recent high survey biomass and strong cohorts of young fish in the survey catch composition also indicated the potential for a recruitment pulse between 2016 and 2018.
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
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.
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.