CCAMLR

A large sample of otoliths from Bigeye Grenadier (Macrouros holotrachys) caught as bycatch in the Toothfish (Dissostichus eleginoides) fishery in subarea 48.3 were measured and weighed and their usefulness as predictors of fish size was determined. Otolith mass provides a good measure of fish length whereas otolith length and width measurements provide less accurate estimates of fish length. Seasonal variations in fish mass with reproductive condition need to be considered if predictions of mass from otolith mass are undertaken. Otolith size/fish size models should be derived for each fish population under investigation. The length of fish chosen in such studies should be representative of the size range consumed by predators.

MtDNA and microsatellite loci were used to investigate the population structure of Patagonian toothfish at two Australian fishing locations (Macquarie Island, five collections; Heard and McDonald Islands (CCAMLR area 58.4.2), four collections) in the Southern Ocean. Additionally, a small sample of toothfish from the Shag Rocks/South Georgia fishing location (CCAMLR area 48.3) was also examined. Striking mtDNA heterogeneity was detected among the three fishing locations; spatial and temporal collections within the same fishing location were not significantly different. There was weak and inconsistent heterogeneity at several microsatellite loci among the ten collections, and no overall differentiation among the three fishing locations. The mtDNA heterogeneity suggests that gene flow between the two Australian fishing locations and more generally among the three locations within the Southern Ocean is restricted.

Two sequential groundfish surveys in January-February 2000 revealed very different distribution of Raja georgiana, rather abundant species on the South Georgia shelf. The adult rays longer 206 mm were not caught during the second survey, the first one did not reveal such anomaly. The reasons which may caused such an absence are discussed.

This research program compared seabird bycatch mitigation strategies over 2 years (1999 and 2000) in 2 major Alaska demersal longline fisheries: the Gulf of Alaska /Aleutian Island Individual Fishing Quota fishery for sablefish and halibut and the Bering Sea catcher-processor longline fishery for Pacific cod. We conducted tests over two years to account for inter-annual variation and allow for improvement and innovation. A key feature of this program was an industry-agency-academic collaboration to identify possible deterrents and test them on active fishing vessels under typical fishing conditions. We report the results of experimentally rigorous tests of seabird bycatch deterrents on the local abundance, attack rate, and hooking rate of seabirds in both fisheries. Based on our results, we recommend a suite of bycatch mitigation measures. Among all deterrents tested, paired streamer lines proved to be the most comprehensive solution. Paired streamer lines successfully reduced seabird bycatch in all years, regions, and fleets (88% to 100% relative to controls with no deterrent), despite the fact that we saw orders of magnitude variation in bycatch across years and in the case of the sablefish fishery, among regions. Paired streamer lines were robust in a wide range of wind conditions and required little adjustment as physical conditions changed. Functionally, paired streamer lines created a moving fence that precluded seabird attacks. Most significantly, this success came with no consequence to catch rates of target-fish or the rate of capture of other bycatch species, thus satisfying our primary goal. Several additional measures are discussed, including eliminating directed discharge of residual bait and offal while setting gear and the need for report card and peer-review systems, as well as the need for national and international action. The full report is available at http://www.wsg.washington.edu/pubs/seabirds/seabirdpaper.html Hard copies will be available at the meeting from Kim Rivera, NMFS, USA

The United States Antarctic Marine Living Resources (U.S. AMLR) program conducted a bottom trawl survey in March, 2001 of the South Shetland Islands. Information on species composition, size composition, spatial distribution, and dietary patterns are presented. Estimates of total stock biomass were computed for eight species: Champsocephalus gunnari, Chaenocephalus aceratus, Chionodraco rastrospinosus, Gobionotothen gibberifrons, Lepidonotothen larseni, Lepidonotothen squamifrons, Notothenia coriiceps, and Notothenia rossii. Biomass estimates were compared to the results from the 1998 U.S. AMLR Survey. For most species, the standing stock has decreased slightly, although in most cases the 95% confidence levels from the 2001 surveys were considerably decreased. The results indicate that stocks of N. rossii have not recovered even after commercial fishing has ceased for 20 years. The overall abundance of finfish in the South Shetland Islands has yet to reach a level at which commercial exploitation would be advisable. The potential role of habitat structure in demersal finfish assemblages in the South Shetland Islands is discussed.

Between March 2000 and April 2001 two commercial fishing vessels undertook trials at South Georgia of a method of fishing for toothfish (Dissostichus eleginoides) using pots. A significant bycatch of lithodid crabs (three species of Paralomis spp.) was encountered. Paralomis spinosissima occurred in shallow water, generally shallower than 700m. P. anamerae, not previously reported from this area, had an intermediate depth distribution from 400 – 800m. P. formosa was present in shallow waters but reached much higher catch levels (and, presumably, densities) between 800 and 1400m. Differences were also noted in depth distribution of the sexes and the size of crabs. Depth, soak time and area were found to significantly influence crab catch rates. Very few crabs (3% of P. spinosissima and 7% of P. formosa) were males above the legal size limit and could therefore be retained. All other crabs were discarded. Most crabs (>99% of P. formosa, >97% of P. spinosissima and >90% of P. anamerae) were lively on arrival on deck and at subsequent discard. Mortality rates estimated from re-immersion experiments indicated that on the vessel which emptied pots directly onto the factory conveyor belt 85% – 90% of crabs would survive discarding, whereas on the vessel where crabs were emptied down a vertical chute prior to being sorted, survivorship was 39% - 58%. P. anamerae was the most vulnerable of the three species to handling onboard and subsequent discarding. P. spinosissima seemed to be more vulnerable than P. formosa.

We conducted a preliminary analysis on the numbers of birds caught as a bycatch in the trawl fishery for icefish (Champsocephalus gunnari) in Subarea 48.3. From December 2000 – February 2001 92 birds were caught, principally black-browed albatross and white-chinned petrel, with 93% of the birds being caught in February. GAM/GLM analysis suggested that month and vessel were significant factors affecting the probability of a haul catching birds, but no significant factors were found that could explain the number of birds caught. Differences in the numbers caught in the last three years also suggest that there may be a year effect. We were unable, with the limited data available, to separate these various hypotheses and identify conclusively the causes of seabird bycatch in the icefish fishery. More work by scientific observers is required to enable effective mitigation measures to be designed for this potential problem. CCAMLR protocols and data formats for such observer studies need to be developed.