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    Fish and invertebrate by-catch from Australian fisheries for
    D. eleginoides and C. gunnari in Division 58.5.2

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    Numéro du document:
    E.M. van Wijk and R. Williams (Australia)
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    Currently, three Australian commercial fisheries operate around Heard and McDonald Islands in CCAMLR Statistical Division 58.5.2. These comprise a trawl and a longline fishery for the Patagonian toothfish, Dissostichus elegionoides and a trawl fishery for mackerel icefish, Champsocephalus gunnari. This paper presents available by-catch information for the three fisheries including estimates of total removals by fishing season and ground, and length composition of rajids and macrourids. Preliminary results from a rajid tagging program are also presented. Total removals of by-catch in the trawl fisheries are estimated to be very low. From 1996/1997 to 2002/2003, a total of 115 tonnes of by-catch was caught in the D. eleginoides trawl fishery and 107 tonnes in the C. gunnari trawl fishery. These values represent less than 1% and 2% respectively, of the total catch weight (target and non-target species) in each fishery. During the 2002/03 season of the longline fishery for D. eleginoides, 23 tonnes of by-catch was caught representing 8% of the total catch. The length range of macrourids and rajids caught in the trawl and longline fisheries is discussed and compared to the length range of the population sampled by research surveys. Eight Bathyraja eatonii have been recaptured to date, resulting in a recapture rate of 1.9% for this species. Tagged rajids exhibit little movement between release and recapture with distances travelled ranging between 1 and 7 nautical miles. The time at liberty varied between 208 and 823 days, with most skates at liberty for approximately one year. Estimates of growth were very low, with average increments of 12 mm per year in total length, 17 mm per year in disk width and 0.1 kg per year in weight. The results presented here, indicate that this species is likely to be very slow growing and/or that the trauma of capture results in at least one year of very slow growth. Growth estimates were lower than those estimated for similar sized species from the northern hemisphere.