WG-FSA-98

The absolute and relative fecundity of Patagonian toothfish inhabiting areas of South Georgia Island and Shag Rocks were studied. The absolute individual fecundity of toothfish in relation to the size of specimens ranged from 56,3 to 567.5 thousands of eggs, averaging 152,9 thousands of eggs. Values of relative individual fecundity of toothfish varied from 4,1 to 13,0 thousands of eggs ( Read More
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Bathymetric maps of two major areas within the South Shetland Islands were generated using several integrated bathymetric databases. These areas comprise the lower South Shetland Island chain from King George Island to Smith Island, and the region around Elephant Island. From the integrated data sets, areas of seabed within the 500 m isobath for six levels of depth strata (0-50 m, 51 - 100 m, Read More
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Bottom trawl surveys were conducted by the United States Antarctic Marine Living Resources program in two major regions of the South Shetland Islands: Elephant Island and the lower South Shetland Islands from King George Island to Livingston Island. Information on species composition, catch levels, size composition, and condition are described and compared between the two regions. Maturity Read More
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Maturity data information obtained by the scientific observers on board the ships Argos Helena and Cisne Verde during August of 1997 -and utilized by the WG-FSA-97 to build the maturity ogives- were age transformed applying the age-size relationship obtained from the specific equations for each sex in samples coming from South Georgia Islands. The results show that the differences are due to Read More
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The United States Antarctic Marine Living Resources (U.S. AMLR) program conducted bottom trawl surveys in March, 1998 of the two major regions of the South Shetland Islands: Elephant Island and the lower South Shetland Islands from King George Island to Livingston Island. Estimates of total stock biomass and spawning stock biomass were computed for six species: Champsocephalus gunnari, Read More
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A 43-day cruise on FV Tierra del Fuego took place in February and March 1997, as part of the New Fisheries Project developed by Chile in Statistical Subareas 88.3, 48.1 and 48.2. During this research study every measure currently in force was used to prevent incidental seabird mortality, carrying out bird observations in each one of the 52 castings with the Spanish-designed longlines as well. Read More
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Results of the February-March 1998 exploratory and experimental fishing operations using pots are described. This research took place during the New Fisheries Project carried out by Chile, with the purpose of determining the presence of Dissostichus spp. in Subareas 48.1, 48.2 and 88.3. In each location where industrial bottom longlines were used, six pots were lowered, three at each end of Read More
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Seabird bycatch arising from longline fishing is known to kill tens of thousands of seabirds each year, and is now acknowledged as representing the most pervasive threat to seabirds, particularly albatrosses, causing widespread declines in populations across the world. However the extent of seabird mortality is poorly known for most of the world's longline fisheries. Information on bird Read More
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Large numbers of seabirds are killed each year within the Australian Fishing Zone (AFZ) by Japanese longline vessels targeting tuna. In recent years the estimated rate of seabird bycatch in the AFZ has been in the order of 0.15 birds 1000 hooks, translating to mortalities of 1000-3500 birds per year. These estimates are absolute minima because not all birds killed remain on hooks to be Read More
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Long term fisheries observer data were used to analyse the influence of a range of environmental variables and mitigation measures upon catch rates of seabirds in the Japanese pelagic longline fishery. In the Australian Fishing Zone (AFZ) seabirds were most likely to be caught on longlines that were set during summer, in southern areas of the zone, and during daylight hours. However, Read More
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Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedea cauta breeding at two sites off Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island Read More
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Various elements of the Generalized Linear Model (GLM) used to standardise toothfish CPUE in Subarea 48.3 are investigated. Problems with crossover between the essentially summer fishery of 1992-1993 prosecuted by Russian vessels and the winter fishery of 1995 onwards prosecuted by other nationalities, coupled with the existence of the experimental fishery in 1994, lead us to suggest that Read More
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Results of published studies on the biology, biomass and distribution of the Antarctic toothfish (Dissostichus mawsoni) were reviewed. The review focused on those aspect of the species which are of importance for the assessment of its biomass and identification of its stocks. The trophodynamics of D. mawsoni are mentioned only in brief. Most published materials refer to studies conducted in Read More
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Studies on DNA microsatellites and a tagging programme both provide information on the degree of interchange of Dissostichus eleginoides (Patagonian Toothfish) between two sites 40 nautical miles apart near Macquarie Island. Five DNA microsatellite loci were identified that showed polymorphism levels appropriate for population structure analysis, and two of these gave results that suggest Read More
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Longline fishing for Patagonian toothfish Dissostichus eleginoides in the South African Exclusive Economic Zone around the Prince Edward Islands commenced in 1996. This paper summarises seabird bycatch during the year July 1997-June 1998. Data on seabird bycatches were obtained from fishery observers aboard all 11 sanctioned fishing trips, representing a fishing effort of 4.3 million hooks. Read More
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A bottom-longline research cruise was carried out between 22 of October and 1 of December 1997. During this experience several submarine mountains were surveyed south to Africa close to the Antarctic Convergence (Meteor) and in the CCAMLR region (Shona, Spiess, western slope of the Bouvet Island, Ob and Lena). The general objective of the cruise was to study the fish populations inhabiting Read More
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Longline sink rates were investigated using Time Depth Recorders on a bottom autoline vessel F.V. San Aotea in New Zealand. The objective of the project was to determine line sink rate, and the effect that adding weights to the line had on its sink rate. The vessel used Mustad autoline equipment that is designed to sink without weights, so non-weighted longline line sink rate data were Read More
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A prerequisite for validation of an aging technique is a clear set of consistent aging criteria to test. Two sets of criteria ate presented for aging the otoliths of Dissostichus eleginoides, one (C1) developed from previous work on the same species; the other (C2) adapted from generalized criteria used to age high latitude fish from the north-west Pacific Ocean. Growth structures were found Read More
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During the 1 997198 season, one vessel, Chilean registered stern trawler Betanzos, fished commercially for mackerel icefish at South Georgia (Subarea 48.3) using a midwater trawl for ten days between 25 December 1997 and 5 January 1998. The total catch of C. gunnari was 5.04 tonnes in 34 hauls. 67% of this catch was taken in just two hauls, confirming the patchy distribution of this species. Read More
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A random stratified trawl survey of Mackerel icefish in 2 populations (Plateau and Shell Bank) in the vicinity of Heard Island enabled a revised estimate of yield for the coming 2 seasons in 1999 and 2000. While the abundances of icefish are lower in 1998 than in 1997, the Age 3 and Age 4 cohorts are still sufficiently strong to provide for a yield greater than estimates of the long term Read More
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A monitoring program of demersal fish in inshore sites of the South Shetland Islands has continued in Potter Cove from 1991 to 1998, covering a continuous sampling period of 15 years and in Harmony Cove, Nelson Island, in the austral summer 1995/96. The decline in trammel net catches of fjord fishes of the species Notothenia rossii and Gobionotothen gibberifrons in relation to the non Read More
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Trends in mean length and maturity stage of toothfish were examined using observer data from the 1998, 1997 and 1996 toothfish seasons. Toothfish are distributed down the shelf slope in relation to their size, an approximately linear relationship existing between depth and fish length. A statistically significant pattern of changing mean length at depth with month was found in both 1997 and Read More
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