CCAMLR

The stomach contents of 190 sub-adult (51-100 cm TL) Antarctic toothfish (Dissostichus mawsoni) captured by bottom longline in the western Ross Sea were analysed. Fish were sampled during the 2005 fishing (Dec 2004 to Jun 2005) season and caught in 398-1678 m depths. Sub-adult D. mawsoni are primarily piscivorous, feeding on a wide variety of small to medium sized fish. Icefish (Channichthyidae) were the most important prey by frequency, weight and IRI, while small notothens (Nototheniidae) were more numerous. Whitson’s grenadier (Macrourus whitsoni), dragonfish (Bathydraconidae), and eel cods (Muraenolepididae) were also important. Glacial squid (Psychroteuthis glacialis) were found in about 20% of stomachs, but only 6% by IRI.
Samples were collected mainly from the continental slope along the northern edge of the Ross Sea. Although the study provides an important comparison of diet of adult and sub-adult fish collected from the same area, the results may not reflect the diet of the main part of the subadult population which is thought to reside on the main shelf to the south. It is therefore recommended that further stomach samples be collected from further south on the Ross Sea shelf.

A toothfish species profile, covering aspects of the biology, fisheries and stock assessment of both toothfish species was completed by Everson (2002). Aspects of the biology of D. mawsoni were summarised by Hanchet et al. (2003), whilst more recent research has been reported in background documents to WG-FSA. The aim of the current work was to collate and summarise existing biological data on D. mawsoni. The report focuses primarily on data collected from the Ross Sea fishery because this is where most of the work has been carried out, but data from the other areas and fisheries have been included when available. It is intended that this report form the basis of a species profile of D. mawsoni as requested at the 2005 CCAMLR meeting (SC-CAMLR XXIV).

The long term monitoring program of demersal fish at inshore sites of the South Shetland Islands has continued at Potter Cove from 2000 to 2006, covering a continuous sampling period of twenty four years, and at Harmony Cove, Nelson Island, in the austral summers from 2001 to 2003. The decline in trammel net catches of fjord fishes of the species Notothenia rossii and Gobionotothen gibberifrons in relation to the non commercially fished Notothenia coriiceps, which was previously reported for the period 1983-1999, is still evident. At Potter Cove, despite an overall increasing trend of N. rossii catches from 1991 to 2006, the actual levels are half of those found in the early 1980s, while those of G. gibberifrons further declined and remain close to zero. At Harmony Cove, the relative abundance of N. rossii showed an increase in years 2002-2003, whereas G. gibberifrons was absent in the catches. These trends are consistent with those observed in scientific cruises on the offshore populations in a similar period. Commercial fishing off the South Shetland Islands in the late 1970s is the most likely explanation for the decrease in recruitment to the inshore sub-populations of N. rossii and G. gibberifrons. No recovery of the stocks of these two fish species was observed, even more than two decades after the end of the commercial fishery. Both, present results of inshore monitoring and those of the offshore cruises since 1998 show that the populations of N. rossii and G. gibberifrons in the South Shetland Islands region cannot, at present, sustain a commercial fishery.

Patagonian toothfish, Dissostichus eleginoides, collections (n-186) from three ocean basins were analysed for Hg concentration and comparisons were made by gender, total length (TL), wet weight (WW), and basin. There was no difference between TL-WW relationships by gender within any basin across the range examined. However, fish were significantly smaller within the Atlantic basin (mean=84.52 cm; 5.57 kg; n=142) than the Pacific (99.07 cm; 9.12 kg; n=15) and Indian (102.72 cm; 14.0 kg; n=29) basins, which were not different from each other. Similarly, Hg concentration did not differ by gender or size across the range examined and was less for Atlantic basin fish ) mean=0.23 ppm) than either Pacific (0.73 ppm) or Indian basin (0.80 ppm) fish, which did not differ.
The Pacific and Indian basin fish had Hg concentrations within the range found for other fish like shark, swordfish, tilefish, and king mackerel, that are considered high in Hg concentration by the U.S. Food and Drug Administration. In contrast, those from the Atlantic basin were found to have similar lower values in fish like haddock, halibut, cod, albacore tuna, and orange roughy.
Explanation of these geographical differences in Hg may be 1) the noted size differences among basins, or 2) the actual sample locations and associated hydrogeographical and oceanographical conditions. For example, sampling sites for the Pacific Ocean lie well outside the Antarctic Convergence whereas the Indian Ocean sites straddle the Convergence. The Atlantic sites lie well within the Antarctic Convergence, suggesting that the Polar Front may provide some type of hydrographic barrier, as suggested in other studies on Patagonian toothfish, to anthropogenic sources of contamination. With a steady global market demand for Dissostichus this could pose a human health risk that has yet to be adequately explored.

The new continuous krill fishing system uses both a small-meshed midwater trawl and a powerful pumping system for continuous pumping the catch out of the trawl bag. It was discussed the potential threats of new technology to Antarctic marine ecosystem. It was shown that application of this fishing technology may result in considerable by-catch of the juvenile fish and larvae in krill fishery.

The Spanish system is used in a range of demersal and semi-pelagic longline fisheries throughout the southern hemisphere and has been the source of a large number of seabird fatalities. An experiment was conducted on a chartered Spanish-rig vessel to improve the sink rate of longlines to reduce interactions with seabirds. The benchmark sink rate was that of integrated weight (IW) longlines, as used by autoline vessels, that are effective in reducing the mortality of white-chinned petrels, one of the world’s most difficult seabird species to deter from baited hooks. Results to shallow depth (0-2 m) were given priority because Spanish system gear, while fast to deeper depths (10-20 m), is slow to clear surface waters. The experiment determined the effect of setting speed (6 knots, 8 knots and 10 knots), distance between weights on longlines (30 m, 40 m and 50 m) and mass of the weights (4 kg, 6 kg and 8 kg) on sink time profiles of longlines. The variable was the sink time to six target depths from 1-20 m as determined by time-depth recorders attached to lines. Separately, a trial was conducted to determine differences in sink rates between traditional Spanish system line weights (netting bags of rocks) and elliptically-shaped steel weights. In the vessel charter experiment there was a statistically significant interaction between setting speed and distance between weights to ? 10 m depth. Overall, distance between weights and mass of the weights were the principal determinants of sink times to target depths. Longlines with weights 30 m apart and either 6 kg or 8 kg traditional weighs, or 40 m and 8 kg weights, most closely approximated the sink profile of IW-autoline in the shallow depth ranges irrespective of setting speed. In the weight-comparison trial 4 kg steel weights and 8 kg traditional weights sank at comparable rates and are considered to be interchangeable. Best practice seabird bycatch mitigation for line setting operations would involve a) setting longlines with weights 30 m apart (minimizes lofting in propeller turbulence), b) use of 5-6 kg elliptical steel weights instead of traditional weights, c) limiting setting speed to the 6-8 knots range, d) lining bait compartments of setting baskets and stern setting surfaces of vessels with marine grade stainless steel (to reduce incidences of hook-ups and line tension astern), e) releasing line weights before line tension occurs (eliminates a source line tension astern), f) use of dual, hydraulically-driven bird scaring streamer lines (to reduce crew work load and improve compliance) to CCAMLR standards and with 50-60 m aerial extent, g) attaching streamer lines to vessels ?5 m either side of the position the hook line leaves the vessel and use of a ‘lazy’ line to increase effectiveness in cross winds and to enable streamer lines to be positioned according to the weather conditions each time longlines are set. Strict compliance to the recommendations above has the potential to eliminate albatross mortality and reduce mortality of deep diving seabird species to very low levels.

F/T Saga Sea is a Norwegian registered factory trawler owned by the Aker Seafoods Antarctic AS, and is licensed to fish krill in Area 48.1-4. Aker has developed a patented new environmental friendly continuous trawling system, named Aker Eco Harvesting System. The system is described in the paper and is based on a conventional trawl with a connected rubber hose to the cod end of the trawl. The catch is brought onboard continuously through a suction driven system. The system is completely closed. The vessel has a processing plant onboard, which is approved for manufacturing food and feed grade products from Antarctic Krill. Approved product categories are krill meal, krill oil, round frozen krill, krill mince and krill protein concentrates. The vessel has so far carried out two fishing trips since 19 June 2006. The last trip started in September. The vessel carries an UK (MRAG) international scientific observer onboard. There is an agreement between the Aker Seafood Antarctic and The Institute of Marine Research in Norway to use Saga Sea as platform for collecting scientific data, and laboratory facilities are installed.

This paper presents an analysis of the distribution of albatrosses and petrels in the area under the jurisdiction of the Western and Central Pacific Fisheries Commission (WCPFC), using data from the BirdLife Global Procellariiform Tracking Database.
• The WCPFC area includes 41% of the global breeding distribution of albatrosses and petrels.
• Albatross distribution is concentrated north of 20ºN and south of 30ºS.
• WCPFC longline fisheries set approximately 100 million hooks each year north of 20ºN and below 30ºS, representing 16% of WCPFC’s total longline fishing effort.
• Some species spend a significant proportion (>40%) of their time in high seas areas. Key high seas areas include the Tasman Sea and areas north of the Hawaiian Islands. The distribution in high seas areas emphasises the importance of WCPFC in bringing about a collaborative approach to reducing seabird bycatch.
• Few tracking data are available for giant-petrels, petrels and shearwaters in the WCPFC area. Range maps indicate that several, including species known to be vulnerable to bycatch, have ranges that span the tropical Pacific

Report from the second meeting of the WCPFC Ecosystem and Bycatch Specialist Working Group 2006, with background on draft seabird recommendations