CCAMLR

In stocks that have been depleted by overfishing, the benefits of additional fisheries removals for research purposes need to be evaluated against the risks that such catches may contribute to delaying the recovery of such stocks. Through simulating a Dissostichus eleginoides stock that has been subjected to varying levels of overfishing and research catches, this study show that stocks can take decades to recover even in the absence of fishing, and apparently low levels of research catches can significantly delay the recovery of a stock. Research catches in excess of 0.6% of B0 should be avoided to ensure that research doesn’t significantly impact on the recovery of depleted stocks in the long term.

Attempts to estimate natural mortality, as a single constant M, simultaneously with other model parameters in integrated assessments via CASAL for the Heard and McDonald Islands (HIMI, CCAMLR Division 58.5.2) Patagonian toothfish (Dissostichus eleginoides) fishery have been unsuccessful. An alternative strategy was adopted whereby the catch-at-age and mark-recapture data were restricted to the main trawl ground in which the longest time series of catches and the great majority of releases and recaptures of tagged fish were available. Catch and releases by age class for this fishery were obtained using proportions-at-length and fishery and year specific age length keys (ALKs) for years 1998 to 2008. A large proportion of the recaptures of fish released in this fishery were aged and these were used to obtain recapture numbers by age class. Two alternative estimation models were programmed in R, based on alternative ordinary differential equations (ODE) for within-year population dynamics. These are the BODE model (Baranov ODE) and the CCODE model (constant catch ODE). Previous studies of the properties of these two models for estimation of M used simulation. In application to the data obtained for the HIMI main trawl fishery, the CCODE model, gave a well-behaved profile for the log-likelihood with the corresponding estimate of M of 0.155, however, the 95% confidence bounds of the estimate were very wide ranging from 0.055 to 0.250 (based on a Poisson over-dispersion estimate of 3). In contrast, the BODE model gave unrealistic estimates of M and the annual fishing mortality rates both when the model was or was not conditioned on the total numbers caught in each year.

A three‐year tagging study in the South of Subarea 48.4 was initiated in the 2008/09 fishing season with the aims of  providing the data required for assessments of the population structure, size, movement and growth of both Dissostichus eleginoides and Dissostichus mawsoni in the South of 48.4; A total of 186 D. eleginoides and 202 D. mawsoni were tagged and released in 2010, leaving a total of 794 tagged fish in the water, respectively. A total of 13 D. eleginoides and 22 D. mawsoni were recaptured in the latest season, including three and six within‐season recaptures, respectively. Macrourids and rajids again dominated bycatch, comprising 15.4% and 1.2% of toothfish catch, respectively. A total of 238 Amblyraja georgiana were tagged and released in 2010 and 3 were recaptured; Approximately 20% of sets were undertaken during daylight hours and no bird entanglements or mortalities were reported; Preliminary stock assessments by different methods estimate a lower stock size of Dissostichus spp. in the South than previously anticipated. In addition there are signs of significant stock depletion towards the northern boundary of the Southern management area. The UK proposes to complete the mark‐recapture experiment in the South of Subarea 48.4 in 2010/11 with a reduced TAC of 30 tonnes.

The target tagging rate of 5 fish per tonne was exceeded by both vessels, with 232 D. eleginoides tagged and released in 2009/10, bringing the total to 1,547 in all seasons; There were 18 D. eleginoides tag recaptures in 2009/10, a total of 72 in all seasons; The length-frequency of 2009/10 captures is consistent with the theory that the bulk of the biomass is dominated by a small number of cohorts. CASAL estimates a large recruitment event in early the early 1990s and faster growth rates than those currently assumed for the 48.3 population CASAL estimates of D. eleginoides population size in the North of 48.4 are very similar to that from the previous season with a B₀ of 1,123 t (compared to 1,127 t in the 2009 assessment) and B₂₀₁₀/B₀ of 92.8%. Sustainable yield calculated according to the CCAMLR decision rules is 41 tonnes. A lower than anticipated number of tag recaptures have come from 2007/08 releases. Removing these from the CASAL assessment reduced B₀ to 963 tonnes though had a minimal effect on B₂₀₁₀/B₀ (89.7%). Sustainable yield omitting 2007/08 tags is 37 tonnes.

In January 2010, the UK carried out the annual groundfish survey in CCAMLR Sub-Area 48.3 on the FV Sil. Seventy-five random hauls were completed with good coverage across the shelf, representing an increase in effort overall compared with surveys carried out in 2008 and 2009 on the same vessel. Catch-weighted length frequencies of mackerel icefish indicated that although 3+ sized fish dominated the population, 2+ and 1+ sized fish were also present, and in larger proportions than in 2009. A mean biomass of 52,329 tonnes was estimated for mackerel icefish, with a lower 1-sided 95% CL of 24,334 tonnes, an increase on the biomass estimate for 2009. Considering the anomalous environmental conditions and low availability of krill to mackerel icefish in the area (evidenced by dietary analysis) in 2009, this increase in biomass was unexpected. The importance of krill in the mackerel icefish diets was greater in 2010 than in 2009 but still remained low compared to historical data, and Themisto gaudichaudii dominated diets in Northern area strata where the largest numbers of mackerel icefish were caught. As seen during the 2009 survey, mackerel icefish remained close to the bottom and very few acoustic marks were observed in the water column during the survey. Catches of Patagonian toothfish were greater than in 2009, but still low compared with historical survey catches. There was however, the first evidence since 2003/04 of a recent recruitment of evident at Shag Rocks, with presence of putative age 2+ fish (29-39cm). Very large catches of marble rockcod were experienced during the 2010 survey, with increased catches across all areas of shelf surveyed around South Georgia and Shag Rocks compared with previous surveys. The mean biomass estimate was 173,223 tonnes, more than ten-fold the estimate for 2008. Catches and biomass estimates for Scotia Sea icefish and South Georgia icefish were also greater than estimates for 2008 and 2009. Exploration of historical marble rockcod catch data and environmental variables is underway, but careful monitoring of all three species should be carried out to determine whether these estimates represent population recovery.

A length based projection model is employed to estimate catch limits for the 2011/12 fishing season for Champsocephalus gunnari in CCAMLR sub area 48.3. The model is initialised using estimated numbers at length derived from survey length  density and biomass density data, removing the need for cohort identification associated with the age based projection model used in previous assessments. Application of the harvest control rule ensuring 75% escapement after a two year projection period yielded a total allowable catch of 2349 tonnes.

The analysis of catch size composition, statistical data on catches and distribution of Antarctic tooth-fish, and tagging data showed that the existing system of fishing subarea partition into SSRUs, open and closed for fishery, resulted in a lack of overall picture of population structure state, quantitative toothfish distribution over the whole aquatory in Divisions 88.1 and 58.4 and did not give an idea of toothfish migrations by tagging results. The mentioned system shortcomings require its revision and conducting of fishery, investigations on toothfish distribution over the whole areal and account of the stock state.

This research makes a contribution to the Agenda Item 8 of the WG-FSA. (Biology, ecology and demography of target and by-catch species) and shows the response of the local population of Dissostichus eleginoides (TOP) from the Area management A (subarea 48.3), after 4 year of closure (2004 to 2008). We noted an increase in the CPUE overtime, mainly associate with the increase in the median size of fish caught, at a mean rate of approximately 1 kg per year/per individual. This result suggests that the sampling in this area should not stop because of its high interest in the monitoring of the recovery of the spawning biomass of the local population in relation to the BOFFFF hypothesis (Big Old Fat Fecund Female Fish), which is very important for strengthening CCAMLR precautionary management in this species.

This paper describes spatial and bathymetric distribution of fish bycatches inside the French EEZ for the longline fishery.

The genus Macrourus is a small group of bentho-pelagic fishes with three species recognized in the Southern Ocean and one in cold temperate to Arctic waters in the North Atlantic Ocean. DNA barcoding revealed low intra-species (0.0-0.002) and inter-species (0.006-0.020) sequence divergences, with four well supported clades among the three Southern Ocean species. Additional specimens collected in the Ross Sea region, and provisionally identified as M. whitsoni, were divided into two COI haplotypes, based on a Restriction Fragment Length Polymorphism (RFLP) test. Three characters counted/scored in the same Ross Sea region specimens classified individuals into two groups: one with 9 pelvic fin rays, pale body colour, and a single row of relatively long teeth, and a second group with 8 pelvic fin rays, dark body colour, and 2 or more rows of finer teeth, that corresponded with the DNA haplotypes. The COI divergence coupled with the meristic and morphometric differences among specimens provisionally identified as M. whitsoni from the Ross Sea region provided strong evidence for two sympatric species: M. whitsoni pale and M. sp dark. The shallow sequence divergences likely indicate either recent evolutionary divergence or slow nucleotide substitution at COI in this genus.