Fishery Report 2022:
Champsocephalus gunnari in Subarea 48.3
CCAMLR Secretariat
12 April 2023
Mackerel icefish, Champsocephalus gunnari Lönnberg, 1905.
Map of the management areas within the CAMLR Convention Area. Subarea 48.3, 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
Fishing for C. gunnari began in Subarea 48.3 in the late 1970s, with large catches taken by Eastern European vessels. Catches peaked in 1983 at a reported 178,824 tonnes. Following concerns about the depletion of stocks, CCAMLR closed the fishery in the early 1990s. The fishery was reopened in 1995, but with a highly conservative catch limit, and was restricted to pelagic trawling to avoid impacts on non-target species. Conservation measures, including requirements to clean nets and ensure that they sink quickly, also reduced incidental mortality of birds. By-catch and incidental mortality is now low.
Currently, the fishing activity in Subarea 48.3 focuses on an area to the northwest of South Georgia. Vessels use pelagic trawls with a minimum mesh size of 90mm. Although in recent years the catch limit for this fishery has been between 1,000 and 5,000 tonnes, there has been little commercial fishing activity.
1.2. Conservation Measures currently in force
The annual catch limit for this fishery (Table 1) is described in Conservation Measure 42-01.
Figure 1: Location of the Management Areas in Subarea 48.3.
1.3. Active vessels
In 2018, when fishing last occurred, 1 vessel participated in this fishery.
1.4. Timeline of spatial management
Catch limits for this fishery have been set biennially since 2012. Catch limits are based on a precautionary harvest control rule, assuming there is no recruitment in the second year of the assessment period. Annual catches, relative to the catch limit, are variable depending on the extent of participation in the fishery. They are also influenced by both interannual variation in the icefish population abundance and the availability of fish to the fishery (i.e., changes in the location and depth of fish). Specific size-based move-on rules apply in this fishery so that a vessel must move at least 5 nautical miles from a location where >10% of C. gunnari are less than 240mm, are detailed in Conservation Measure 42-01, paragraph 4.
The location of management areas in this Subarea is shown in Figure 1.
2. Reported catch
2.1. Latest reports and limits
Reported catches of C. gunnari are presented in Table 1. In
this fishery, since 1980, the catch of C. gunnari reached a
maximum of 178,824 tonnes in 1983. In 2018, 1 tonne of C.
gunnari was caught. There has been no fishing since 2018.
| Season | Number of vessels | Catch limit (tonnes) | Catch |
|---|---|---|---|
| 1980 | 1 | 8795 | |
| 1981 | 1 | 27903 | |
| 1982 | 1 | 54040 | |
| 1983 | 1 | 178824 | |
| 1984 | 1 | 35743 | |
| 1985 | 1 | 628 | |
| 1986 | 1 | 21008 | |
| 1987 | 1 | 80586 | |
| 1988 | 2 | 11473 | |
| 1989 | 1 | 0 | |
| 1990 | 1 | 8030 | |
| 1991 | 1 | 41 | |
| 1992 | 1 | 0 | |
| 1993 | 1 | 0 | |
| 1994 | 1 | 0 | |
| 1995 | 1 | 0 | |
| 1996 | 1 | 0 | |
| 1997 | 1 | 0 | |
| 1998 | 1 | 4520 | 6 |
| 1999 | 1 | 4840 | 265 |
| 2000 | 2 | 4036 | 4041 |
| 2001 | 5 | 6760 | 1433 |
| 2002 | 5 | 5557 | 2663 |
| 2003 | 3 | 2181 | 1972 |
| 2004 | 6 | 2887 | 2758 |
| 2005 | 7 | 3574 | 201 |
| 2006 | 5 | 2244 | 2177 |
| 2007 | 5 | 4337 | 4339 |
| 2008 | 5 | 2462 | 2479 |
| 2009 | 5 | 3834 | 1827 |
| 2010 | 3 | 1548 | 1 |
| 2011 | 2 | 2305 | 2 |
| 2012 | 3 | 3072 | 984 |
| 2013 | 3 | 2933 | 1326 |
| 2014 | 4 | 4635 | 33 |
| 2015 | 2 | 2695 | 270 |
| 2016 | 1 | 3461 | 2 |
| 2017 | 2 | 2074 | 110 |
| 2018 | 1 | 4733 | 1 |
| 2019 | – | 3269 | – |
| 2020 | – | 3225 | – |
| 2021 | – | 2132 | – |
| 2022 | – | 1457 | – |
| Total catches <5t reflect catches from research surveys only |
2.2. By-catch
Catch limits for the most common by-catch species; humped rockcod (Gobionotothen gibberifrons), marbled rockcod (Notothenia rossii), grey rockcod (Lepidonotothen squamifrons), South Georgia icefish (Pseudochaenichthys georgianus) and blackfin icefish (Chaenocephalus aceratus) are defined in Conservation Measure 33-01 and shown for each fishing season since 2004 in Table 2. Conservation Measure 33-01 sets by-catch limits for all fisheries in Subarea 48.3; for this reason the catch limits for by-catch species can be greater than the catch limits for the targets species. By-catch is consistently low in this pelagic fishery.
Specific by-catch related move-on rules (whereby a vessel must move at least 5 nautical miles from a location where significant amounts of by-catch were hauled) are detailed in Conservation Measure 42-01, paragraph 6.
| Season | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) | Catch Limit (tonnes) | Reported Catch (tonnes) |
|---|---|---|---|---|---|---|---|---|---|---|
| 2004 | 1470 | 0 | 300 | 0 | 300 | 0 | 300 | 2 | 2200 | <1 |
| 2005 | 1470 | <1 | 300 | <1 | 300 | <1 | 300 | 25 | 2200 | 1 |
| 2006 | 1470 | 0 | 300 | 1 | 300 | 0 | 300 | 6 | 2200 | <1 |
| 2007 | 1470 | <1 | 300 | 0 | 300 | 0 | 300 | <1 | 2200 | 0 |
| 2008 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | <1 | 2200 | <1 |
| 2009 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | <1 | 2200 | <1 |
| 2010 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | <1 | 2200 | 0 |
| 2011 | 1470 | 0 | 300 | 0 | 300 | 0 | 300 | <1 | 2200 | 0 |
| 2012 | 1470 | <1 | 300 | <1 | 300 | 24 | 300 | <1 | 2200 | <1 |
| 2013 | 1470 | <1 | 300 | <1 | 300 | <1 | 300 | <1 | 2200 | <1 |
| 2014 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | 2 | 2200 | 1 |
| 2015 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | <1 | 2200 | <1 |
| 2016 | 1470 | 0 | 300 | 0 | 300 | 0 | 300 | 0 | 2200 | 0 |
| 2017 | 1470 | <1 | 300 | <1 | 300 | 0 | 300 | <1 | 2200 | <1 |
| 2018 | 1470 | 0 | 300 | 0 | 300 | 0 | 300 | <1 | 2200 | 0 |
| 2019 | 1470 | – | 300 | – | 300 | – | 300 | – | 2200 | – |
| 2020 | 1470 | – | 300 | – | 300 | – | 300 | – | 2200 | – |
| 2021 | 1470 | – | 300 | – | 300 | – | 300 | – | 2200 | – |
| 2022 | 1470 | – | 300 | – | 300 | – | 300 | – | 2200 | – |
2.3. Incidental mortality of seabirds and marine mammals
A summary of seabird mortality in this fishery in recent years is presented in Table 3. The three most common species injured or killed in this fishery were white-chinned petrel (Procellaria aequinoctialis), grey-headed albatross (Thalassarche chrysostoma) and black-browed albatross (Thalassarche melanophris).
The level of risk of incidental mortality of birds in Subarea 48.3 remains at category 5 (high) (SC-CAMLR-XXX, Annex 8, paragraph 8.1).
Conservation Measure 25-03 applies to this fishery. It sets out technical measures to minimise bird by-catch and relates to: net monitoring cables, vessel lighting, discarding of offal, net cleaning, net sinking (nets are most likely to trap birds when they are on the surface of the water) and streamer lines (bird scarers).
Conservation Measure 42-01 has a further mitigation measure whereby, should any vessel catch a total of 20 birds, it shall cease fishing and shall be excluded from further participation in the fishery in that year.
| Season | Procellaria aequinoctialis | Thalassarche chrysostoma | Thalassarche melanophris | Other |
|---|---|---|---|---|
| 2001 | 6 | 1 | 10 | |
| 2003 | 14 | 3 | ||
| 2004 | 34 | 1 | 6 | |
| 2005 | 1 | 6 | 1 | |
| 2006 | 18 | 1 | 18 | 2 |
| 2007 | 3 | 1 | ||
| 2008 | 3 | 2 | ||
| 2009 | 3 | 2 | 4 | 2 |
| 2010 | 1 | 1 | ||
| 2013 | 1 | |||
| 2017 | 3 |
There were no observations of mammal mortalities reported by vessels in this fishery.
3. Illegal, Unreported and Unregulated (IUU) fishing
There has been no evidence of illegal, unreported and unregulated IUU fishing activity in this fishery.
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 by-catch by coarse taxonomic groups given the taxonomic expertise required to discriminate similar species. Observers collect biological information on icefish and by-catch specimens at a finer taxonomic resolution, as well as data on individual specimens such as size and maturity.
Summaries of data reported to CCAMLR for the past five years are given in Tables 4 and 5.
| Data source | Data class | Variable | 2018 | 2019 | 2020 | 2021 | 2022 |
|---|---|---|---|---|---|---|---|
| Vessel crew | by-catch | taxa identified | 2 | – | – | – | – |
| records | 2 | – | – | – | – | ||
| Observer | mackerel icefish | specimens examined | 274 | – | – | – | – |
| length measurements | 274 | – | – | – | – | ||
| weight measurements** | 124 | – | – | – | – | ||
| sex identifications** | 184 | – | – | – | – | ||
| maturity stage identifications** | 184 | – | – | – | – | ||
| gonad weight measurements** | 0 | – | – | – | – | ||
| otolith samples** | 0 | – | – | – | – | ||
| **: Voluntary records | |||||||
| *: Species-dependent records |
| By-catch group | Variable | 2018 | 2019 | 2020 | 2021 | 2022 |
|---|---|---|---|---|---|---|
| Last data in 2017 |
4.3. Length frequency distributions
Recent length frequency distributions of the catches of C. gunnari across the entire subarea and in Management Areas 483B and 483C are shown in Figure 2. 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.
Differences in length distribution have been noted between Shag Rocks and South Georgia, although these differences are not thought to represent separate stocks for stock assessment purposes.
Figure 2. Annual length frequency distributions of Champsocephalus gunnari caught in Subarea 48.3. The number of hauls from which fish were measured (N) and the number of fish measured (n) in each year are indicated. Note: length frequency distributions are only shown where more than 150 fish were measured in a given season/area.
5. Research
5.1. Status of the science
Champsocephalus gunnari play an important role in the ecosystem of the South Georgia shelf as predators of krill (Euphausia superba), other euphausiids and the hyperiid amphipod (Themisto gaudichaudii) and as prey species of fur seals and gentoo penguins. Champsocephalus gunnari may also be consumed by juvenile toothfish in years of high C. gunnari abundance at Shag Rocks.
Estimates of C. gunnari standing stock have been shown to vary in relation to krill abundance at South Georgia, and in years of poor krill availability, C. gunnari condition is poorer and larger quantities are likely to be consumed by both fur seals and gentoo penguins, which are normally krill-dependent predators.
Preliminary analysis of long-term data series from UK trawl surveys (since 1986) indicates that abundance of previously overexploited fish (C. gunnari and N. rossi) may now be slowly increasing (WG-FSA-17/44). Time-series analysis of length-frequency data of C. gunnari from five Argentine surveys between 1993 and 2013 also indicates a steady increase in densities of adult fish (WG-FSA-13/65).
The UK undertook a groundfish survey of CCAMLR Subarea 48.3 on the FV Sil between the 27th January and 5th February 2019 (WG-FSA-2019/20). A total of 73 random and representative hauls were completed covering depths of between 108 and 352m. Overall biomass of Chamsocephalus gunnari was calculated at 50,897 tonnes with a lower 1-sided 95% interval estimate of 30,288 tonnes. This is lower than in 2017, but is comparable with the long term average. The highest catches were on the moraine banks of the two northern strata and at the western end of Shag Rocks, with one high catch recorded in the South West stratum. Clear regional differences in C. gunnari diet composition were observed. At Shag Rocks Euphausid spp. made the largest contribution to icefish diet, however the amphipod Themisto sp. dominated the diet around South Georgia. Based on the Index of Relative Importance, the importance of E. superba as a prey species varied across the four regions at South Georgia, ranging from 10.48% IRI in the South West to 33.49% IRI in the South East.
The UK undertook a groundfish survey of CCAMLR Subarea 48.3 on the FV Robin M Lee from 7th to 17th May 2021 (WG-FSA-2021/12). Seventy-seven random trawls were completed covering depths of 105 to 354m. The biomass of mackerel icefish, Chamsocephalus gunnari, was estimated at 18,013 tonnes with a lower 1-sided 95% interval estimate of 10,627 tonnes. This is one of the lowest biomass estimates in the survey series. The highest catches were in the SW area, with low catches in the NW area, which are the main commercial fishing grounds and usually have the largest survey catches.
5.2. Advice by the Scientific Committee
The limits on the fishery for C. gunnari in Subarea 48.3 for the forthcoming season are defined in Conservation Measure 42-01.
6. Stock status
6.1. Summary of current status
A stratified bootstrap of the UK 2021 demersal fish survey icefish catch density and catch rate data indicate a precautionary biomass estimate of 22,047 tonnes (lower one sided 5th percentile: 13,279 tonnes) within Subarea 48.3 (see Stock Assessment Report). Projections for the 2022 and 2023 seasons applying the CCAMLR Decision Rule lead to a recommendation from Working Group FSA to the Scientific Committee that the catch limit for C. gunnari in Subarea 48.3 should be set at 1,457 tonnes for 2022 and 1,708 tonnes for 2023.
6.2. Assessment method
The use of a length-based model to set catch limits for C. gunnari in Subarea 48.3 was endorsed at the 2010 meeting of the Working Group on Fish Stock Assessment (WG-FSA-10) (SC-CAMLR-XXIX, Annex 8, paragraph 5.164). The assessment used survey data on length densities and biomass density without the need to identify age-specific cohorts. Methods of aggregating the length distributions from multiple hauls using a mean of positive values (as previous assessments in this subarea), or a sum (equivalent to a mean of all values) were considered by WG-FSA-17 (WG-FSA-17/51). It was agreed that the assessment should change to using the sum, which reduces the likelihood of over-representing young fish in the population length distribution when small fish are clustered in particular survey strata.
The CCAMLR harvest control rule, using a length-based approach, has been demonstrated to provide robust precautionary estimates of catch limits and exploitation rates for C. gunnari in Subarea 48.3 (WG-SAM-13/31 Rev. 1).
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.