Fishery Report 2020:
Dissostichus eleginoides and Dissostichus mawsoni in Subarea 48.4
CCAMLR Secretariat
16 March 2021
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, “2020” refers to the 2019/20 CCAMLR fishing season (from 1 December 2019 to 30 November 2020).
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.
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.
According to the Stock Assessment of this fishery, observed recruitment is characterised by a larger 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.
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.
1.3. Active vessels
In 2020, 2 vessels 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 both species within the directed fishing area specified in Conservation Measure 41-03.
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 2020, 19 tonnes of D. eleginoides and 44 tonnes of D. mawsoni were caught.
| Season | Number of vessels | Catch limit (tonnes) | D. eleginoides | D. mawsoni | Estimated IUU catch (tonnes) |
|---|---|---|---|---|---|
| 1990 | 1 | 0 |
|
||
| 1992 | 1 | 30 |
|
||
| 1993 | 1 | 10 |
|
||
| 2005 | 1 | 100 | 27 |
|
|
| 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 |
|
2.2. By-catch
Catch limits for by-catch species groups (macrourids, skates (Rajids) 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 (macrourids, skates (Rajids) 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: from 2005 to 2008 there were no specified limits, from 2009 to 2013 there was an overall by-catch limit for macrourids and skates in Subarea 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.
| Season | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) | Number Released | Catch Limit (tonnes) | Reported Catch (tonnes) |
|---|---|---|---|---|---|---|---|
| 1990 | 0 | <1 | 0 | <1 | 0 | 0 | <1 |
| 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 |
The distribution of skates and macrourids in Subarea 48.4 has been investigated and their distributions described in WG-FSA-09/17 and 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 almost entirely comprise Whitson’s grenadier (Macrourus whitsoni). Subsequent taxonomic studies (including genetic analyses) now indicate that the Macrourus 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 vulnerable marine ecosystems (VMEs), including benthic communities and benthos such as seamounts, hydrothermal vents and cold-water corals.
2.4. Incidental mortality of seabirds and marine mammals
In 2017, one Southern giant petrel (Macronectes giganteus) was killed in the fishery in Subarea 48.4. 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. Length frequency distributions
The recent length frequency distributions of D. eleginoides and D. mawsoni caught in this fishery are presented in Figures 2 and 3. 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 2). A second mode of smaller fish (75cm) is evident in 2010 and develops throughout the remainder of the time series, indicating a recruitment pulse.
The length frequency distribution of D. mawsoni (Figure 3) 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 2. 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.
Figure 3. 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.
4.3. 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 also followed this requirement, and both vessels fishing in 2015 achieved tag-overlap statistics of 83-90%.
To date in this area, 2401 D. mawsoni have been tagged and released (125 have been recaptured, 111 of which were released in this area; Table 3), and, 4036 D. eleginoides have been tagged and released (511 have been recaptured, 480 of which were released in this area; Table 4).
One tagged D. eleginoides has also moved into Subarea 48.4 from Subarea 48.3 (WG-FSA-14/29 Rev. 1; 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, 09/18 and 16/40 Rev. 1 provided a comprehensive analysis of the catch distribution of the two Dissostichus species in Subarea 48.4.
| Season | Tagged | 2009 | 2010 | 2011 | 2012 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 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 | 6 | |||||||||
| 2018 | 161 | 3 | 1 | 1 | 5 | ||||||||
| 2019 | 168 | 2 | 6 | 8 | |||||||||
| 2020 | 229 | ||||||||||||
| Total | 2401 | 111 |
| Season | Tagged | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 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 | 73 | ||
| 2009 | 558 | 3 | 16 | 12 | 11 | 8 | 2 | 5 | 3 | 3 | 1 | 4 | 68 | |||
| 2010 | 418 | 2 | 12 | 2 | 12 | 4 | 1 | 4 | 2 | 2 | 2 | 3 | 46 | |||
| 2011 | 222 | 2 | 3 | 4 | 2 | 1 | 1 | 1 | 14 | |||||||
| 2012 | 302 | 7 | 3 | 2 | 2 | 2 | 5 | 3 | 1 | 25 | ||||||
| 2013 | 470 | 23 | 19 | 15 | 7 | 1 | 4 | 3 | 72 | |||||||
| 2014 | 223 | 20 | 12 | 9 | 1 | 2 | 2 | 46 | ||||||||
| 2015 | 226 | 11 | 12 | 7 | 4 | 1 | 35 | |||||||||
| 2016 | 225 | 5 | 1 | 4 | 3 | 13 | ||||||||||
| 2017 | 159 | 1 | 1 | 1 | 2 | 5 | ||||||||||
| 2018 | 87 | 1 | 3 | 4 | ||||||||||||
| 2019 | 73 | 3 | 3 | |||||||||||||
| 2020 | 102 | |||||||||||||||
| Total | 4036 | 480 |
5. Research
Historically, 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-19/27).
6. Stock status
6.1. Summary of current status
A CASAL based assessment of D. eleginoides indicated that the stock was at 67% of B0 in 2019 (WG-FSA-19/29).
The five-year (2015-2019) average biomass of D. mawsoni in this Subarea, estimated from mark-recapture data was 1,187 tonnes (WG-FSA-19/27).
6.2. Assessment method
The stock of D. eleginoides in this Subarea is assessed using a combined-sex, single-area integrated CASAL stock assessment (WG-FSA-19/29).
A Preliminary tag-recapture based population assessment of D. mawsoni was presented in 2019 (WG-FSA-19/27).
6.4. Year of last assessment, year of next assessment
Assessments are reviewed biennially, the last assessment for D. eleginoides was in 2019.
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. 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.
There is no formal evaluation of the impacts of climate change and environmental variability available for this particular fishery.
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.