CCAMLR

ABSTRACT
Prior to the 2009/10 fishing season, the Secretariat allocated starting positions for research hauls in the exploratory fisheries in Subareas 48.6 and 58.4 (except on BANZARE Bank were positions were specified in Conservation Measure 41-07). For each of the 12 notifying vessels, up to 8 starting positions were provided for each stratum in each SSRU notified, and vessels were required to complete 5 research hauls in each stratum (total of 10 research hauls per SSRU). In all, 1133 starting positions were allocated for 84 vessel-SSRU combinations. As of June 2010, three vessels had fished in these exploratory fisheries in 2009/10, and had deployed a total of 129 research hauls in accordance with the conservation measures and allocated positions. Overall the vessels adhered to the research fishing protocol. Three types of difficulties and/or limitations were evident :

a) Sea-ice along the Antarctic coastline had prevented some vessels from reaching allocated positions in the continental SSRUs (e.g. 486D, 5841C and 5841G); however, the vessels were able to deploy research hauls in alternative positions determined by vessels.

b) The deployment of research hauls in alternative positions determined by vessels had resulted in some hauls being set in depths greater than 2500 m.

C) Some vessels did not achieve the required 5 hauls per stratum.

Observer data collected on longliners between 2003 and 2009 were analysed to look at the levels of depredation caused by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) around South Georgia. Since 2003, cetaceans have been observed on 22% of 14 300 observed lines, with killer whales present on 3.8% and sperm whales on 17.7% of lines. Killer whales appear in pod sizes normally of 4 to 10 animals, and often appear to actively seek out fishing vessels and ‘strip’ the line of a large number of toothfish, usually depressing CPUE by about 50%. Sperm whales occur in smaller pod sizes, normally between 1 and 4 animals and have a relatively lower impact on catches, depressing CPUE by up to 20%. Sperm whales have been more frequently encountered in recent years, occurring in larger pod sizes, whereas killer whale encounters and pod sizes have remained relatively constant. Most interactions from sperm whales occur during May at the start of the season with the sightings becoming fewer towards the end of the season in August. Killer whale interactions appear to be more consistent with no obvious pattern between months. Both species demonstrate an east to west migration throughout the season that is not related to the pattern of fishing effort. By comparing catch rates with and without the presence of cetaceans, accounting for other determinants of toothfish CPUE through a generalised linear model, it is estimated that the amounts of toothfish removed from longlines by cetaceans have varied between 1% and 8% of the declared catches over the period 2003–2009, with an average of 3.6%.

Patagonian toothfish (Dissostichus eleginoides) is a large notothenioid fish that supports valuable fisheries throughout the Southern Ocean. D. eleginoides are found on the southern shelves and slopes of South America and around the sub-Antarctic islands of the Southern Ocean. Patagonian toothfish are a long-lived species (> 40 years), which initially grow rapidly on the shallow shelf areas, before undertaking an ontogenetic migration into deeper water. Although they are active predators and scavengers, there is no evidence of large-scale geographic migrations and studies using genetics, biochemistry, parasite fauna and tagging indicate a high degree of isolation between populations in the Indian Ocean, South Georgia region and the Patagonian Shelf. Patagonian toothfish spawn in deep-water (circa. 1000 m) during the austral winter, producing pelagic eggs and larvae. Larvae switch to a demersal habitat at around 100 mm (1 yr old), and inhabit relatively shallow water (< 200m) until 6-7 years of age, when they begin a gradual migration into deeper water. As juveniles in shallow water, toothfish are primarily piscivorous, consuming the most abundant, suitably sized, local prey. With increasing size and habitat depth the diet diversifies and includes more scavenging. Toothfish have weakly mineralised skeletons and a high fat content in muscle, which helps neutral buoyancy, but limits swimming capacity. Toothfish generally swim with labriform motion, but are capable of more rapid sub-carangiform swimming when startled. Toothfish were first caught as a by-catch (as juveniles) in shallow trawl fisheries but, following the development of deep-water longlining, a fishery rapidly developed throughout the Southern Ocean. The initial rapid expansion of the fishery, which led to a peak of over 40,000 tonnes in reported landings in 1995, was accompanied by problems of bird by-catch and over-exploitation as a consequence of illegal, unreported and unregulated fishing. These problems have now largely been addressed, but continued vigilance is required to ensure the species is sustainably exploited and the ecosystem effects of the fisheries are minimised.

Antarctic silverfish (Pleuragramma antarcticum) is a key link between plankton and the community of top predators in the shelf waters of the Ross Sea. In spite of their abundance and important role in Antarctic food chains, very little is known of many ecological and biological aspects of this species. A combined trawl and acoustic survey of silverfish was carried out on the western Ross Sea shelf during the New Zealand International Polar Year Census of Antarctic Marine Life research voyage on R.V. Tangaroa in February–March 2008. Multi-frequency acoustic data (12, 38, 70 and 120 kHz) allowed discrimination of silverfish marks from those of krill and other associated species. Mark identification was achieved using targeted midwater trawls. Additional midwater and demersal trawls were carried out at randomly selected locations over the shelf as part of the core biodiversity survey. Silverfish were widely distributed over the Ross Sea shelf. Adult silverfish tended to form layers at 100–400 m depth and were some times present close to the bottom, where they were frequently caught in demersal trawls shallower than 500 m. A weak layer at about 80 m depth was associated with juvenile silverfish of 50–80 mm standard length. Acoustic backscatter strength from both silverfish and krill marks increased with increasing frequency (i.e., was highest at 120kHz), which is characteristic of species without an air-filled swimbladder. Acoustic target strengths (TS) for silverfish at 12, 18, 38, 70, and 120 kHz were estimated from anatomically detailed scattering models based on computed tomography (CT) scans of frozen specimens. The relationship between TS and fish length at 38 kHz was sensitive to estimates of density and sound speed contrast within the fish, especially for small specimens (less than 110 mm SL). Our best estimate of the acoustic biomass of silverfish in the study area was 592 000 t (95% confidence interval 326 000–866 000 t). However, the biomass of juvenile silverfish was highly uncertain due to large differences between TS model results.

Demersal fishes were sampled using a large fish trawl during two surveys carried out in February and March 2004 and 2008 in the Ross Sea, and around seamounts and islands just to the north at 66°S. The distribution and abundance of 65 species collected in these surveys were examined to determine if demersal fish communities varied throughout the area, and what environmental factors might influence this. Species accumulation with sample frequency did not reach an asymptote, but the rate of new species was low suggesting data were adequate for describing the main components of the communities. Three broad assemblages were identified, in the southern Ross Sea (south of 74°S), central–northern Ross Sea (between latitudes 71°–74°S), and the seamounts further north (65°–68°S) where some species more typical of sub-Antarctic latitudes were observed. Multivariate analyses indicated that environmental factors of seafloor rugosity (roughness), temperature, depth, and current speed were the main variables determining patterns in demersal fish communities.

We measured the otolith chemistry of adult Scotia Sea icefish (Chaenocephalus aceratus), a species with a long pelagic larval phase, along the Antarctic Circumpolar Current (ACC) and compared the chemistry with simulated particle transport using a circulation model. Material laid down in otolith nuclei during early life showed strong heterogeneity between the Antarctic Peninsula and South Georgia consistent with a population boundary, and evidence of finer-scale heterogeneity between sampling areas on the Antarctic Peninsula. At South Georgia, the nucleus chemistry was similar between the eastern and northern shelves, indicating a single, self-recruiting population. Consistent with the otolith chemistry, simulations of the large-scale circulation predicted that particles released at 100-300m depth on the Antarctic Peninsula shelf during spring, corresponding to hatching of icefish larvae from benthic nests, are transported in the southern ACC, missing South Georgia but following trajectories along the south Scotia Ridge instead. These results suggest the timing of release and position of early life stages in the water column substantially influence the direction and extent of connectivity. Used in complement, the two techniques promise an innovative approach to generate and test predictions, and resolve early dispersal and connectivity of populations related to the physical circulation of oceanic systems.

Incidental seabird mortality associated with longline commercial fishing is a worldwide conservation concern. To build conservation strategies it is essential to estimate likelihood of seabird bycatch and amount of overlap between bird’s foraging and commercial fishing areas. We tracked 21 adult white-chinned petrels (Procellaria aequinoctialis) breeding on Kerguelen Island, Southern Indian Ocean, during breeding period in 2006 and 2008. At-sea foraging distribution of white-chinned petrels was mainly confined in Antarctic waters. Commercial longline fisheries targeting toothfish were operating in both French Exclusive Economic Zone (EEZ) and other Commission for the Conservation of Antarctic Marine Living Resources areas during the study. We analysed concurrent data on the position of both birds and vessels to estimate overlap. Static analysis using indices (home range and utilization distribution overlap) revealed that at a large scale spatial and temporal overlap occurred and varied among areas and with breeding stage. Dynamic analysis (detection for each bird location of any operating vessel within a time/space window) revealed few overlap at a small scale. Our study revealed a mismatch between large and small scale overlap estimates, suggesting that birds and vessels occupy the same overall zone with infrequent co-occurrence (19% of birds in the vicinity of vessels). This result was confirmed by the relatively low occurrence of fishery-related items (4 to 22%) in chick food samples. However given the large size of seabirds populations, overall large numbers of birds overlap with vessels and Management Authorities should maintain and promote strict mitigation measures implementation to further reduce bycatch.