WG-FSA-01

The history of the fishery for Patagonian toothfish in the Prince Edward Islands EEZ is reviewed briefly. It is characterised by very large illegal catches and a sharply declining longline CPUE trend. Application of a simple age-structured production model provides robust indication that the spawning biomass has been depleted to at most a few percent only of its pre-exploitation level. Read More
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New Zealand has undertaken a tag recapture study of skates (Family Rajidae) in Subarea 88.1. The objective of the programme is to determine the probability of released skates surviving. Skates have been tagged in the 1999/00 and 2000/01 seasons. Results from 1999/00 were presented in WG-FSA-00/55. This paper provides a brief update on the 2000/01 results and the tagging protocol in use.

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.

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 Read More
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Breeding grey-headed albatross Thalassarche chrysostoma, tracked from Marion Island (Prince Edward Islands) during November–December 1997 and January–February 1998, showed a strong association with mesoscale oceanographic features, as identified by sea surface height anomalies, in the southern Indian Ocean. During incubation, most birds foraged to the north of the island, at the edges of Read More
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Concerning numbers of Wandering Albatrosses Diomedea exulans are killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and large chick-rearing, birds foraged farther away from Read More
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The foraging range and principal feeding areas of White-chinned Petrels breeding at South Georgia were determined using satellite telemetry. Foraging trips during incubation lasted 12–15 days and covered 3000–8000 km and 2–11 days and 1100–5900 km during chick-rearing. Adults covered less distance per day during chick-rearing (71 km) than during incubation (91 km) but the proportion covered at Read More
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Commercial fishing is having an increasingly negative impact on marine biodiversity with over 70% of the world’s fish stocks being fully exploited and in many cases overexploited. On top of this, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has granted commercial fishing permits in the most remote marine environment on earth, the high latitude Southern Read More
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The population structure of black-browed (Thalassarche melanophris and T. impavida) and grey-headed (T. chrysostoma) albatrosses was examined using both mitochondrial DNA (mtDNA) and microsatellite analyses. mtDNA sequences from 73 black-browed and 50 grey-headed albatrosses were obtained from five island groups in the Southern Ocean. High levels of sequence divergence were found in both taxa Read More
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This paper considers a class of survey patterns for a toothfish long lining fishery. These survey patterns are characterised by a minimum mutual separation distance and a shot selection criteria. The shot selection criteria can be either that locations of known good quality are preferentially selected or that locations are selected at random. The landscape and fishery are simulated in a Read More
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The fishery for Patagonian toothfish is one of the most valuable in the CCAMLR Area. Age based models are used to assess the status of the stocks of this species. Although age can be estimated using otoliths it has proven difficult for these to be validated. During a recent trawl survey the length density of juvenile toothfish in the catches had a clearly defined polymodal distribution. The Read More
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Tristan da Cunha and Gough Islands in the central South Atlantic Ocean support globally important seabird populations. Two longline fisheries occur within Tristan's Exclusive Economic Zone: a pelagic fishery for tunas and a demersal fishery for bluefish and alfoncino. Fishery observers have accompanied all three licensed demersal cruises. Despite attracting considerable numbers of birds and Read More
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A series of longline sink-rate trials were conducted with and without weights, from an autoline fishing vessel working the New Zealand ling (Genypterus blacodes) longline fishery on the Chatham Rise, New Zealand during July and August 1998. The autoline equipment is designed to sink without weights, and non-weighted longline line sink data were collected first to provide baseline information. Read More
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1. Several albatross species, including the wandering albatross Diomedea exulans , have shown marked declines in abundance throughout their range. These seabirds are frequently taken as by-catch in longline fisheries and this mortality has been implicated in the population declines.
2. We developed a deterministic, density-dependent, age-structured model for assessing the effects of Read More
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Revisions to the Generalised Yield Model provide for re-estimating the recruitment series from survey data for each value of natural mortality used in the assessments, whenever it is altered over the range of uncertainty in M factored into the assessment process. Data from outputs from mixture analyses from surveys are input to the GYM in raw form. An example file is provided. Consequently, Read More
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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. Read More
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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 Read More
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We report on the population changes of five species of Procellariiform seabirds breeding at Marion Island: wandering albatross (Diomedea exulans), grey-headed albatross (Thalassarche chrysostoma), northern giant petrel (Macronectes halli), southern giant petrel (M. giganteus), and white-chinned petrel (Procellaria aequinoctalis). The four large surface-nesting species (wandering albatross, Read More
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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 Read More
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Age based fishery population models require information on size at age of the fished population and the commercial catch. Age-length keys can be produced by standardised random sampling of the commercial catches. This information does not necessarily reflect the size at age of the fished population and may be seriously biased. Through the use of a model, and using the Patagonian toothfish as Read More
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A large body of data and techniques are available for re-assessing the biological parameters and recruitment of Patagonian toothfish, Dissostichus eleginoides, in the Heard Island region. A new survey of the Heard Island Plateau was undertaken in May - June 2001, providing the sixth survey over 11 years on this stock with other surveys including part of this stock. This paper describes the Read More
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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 Read More
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Interactions between seabirds and longline fishing can cause incidental bird mortality and reduced gear efficiency. The potential for solving these problems by using a bird-scaring streamer line and a line shooter was investigated in commercial longlining in the northern Atlantic off the coast of Norway. We compared the bycatch rate of northern fulmars Fulmarus glacialis, the loss rate of Read More
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The incidental mortality of seabirds in tuna longline fisheries is estimated for the continental South African Exclusive Economic Zone (EEZ). Fishery observers accompanied 13 fishing trips and observed 108 sets (143 260 hooks) during the period 1998–2000. Despite most lines being set at night, seabird bycatch rates were high, with a mean of 1.6 birds killed per 1 000 hooks. Japanese vessels (1 Read More
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Seabird by-catch is summarised for the period July 2000-June 2001 for sanctioned longline fishing for Patagonian toothfish Dissostichus eleginoides in South Africa’s Exclusive Economic Zone around the Prince Edward Islands. There was a slight increase in the number of fishing trips and hooks set in 1999/2000. The number of seabirds killed dropped dramatically from 268 in 1999/2000 to 76 in Read More
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Sanctioned longline fishing for Patagonian toothfish around the Prince Edward Islands (a globally important seabird breeding site) commenced in 1996 following high levels of Illegal, Unregulated and Unreported (IUU) fishing. Independent fishery observers accompanied all but two sanctioned trips between 1996 and 2000, allowing a thorough excellent understanding of the impact of this fishery on Read More
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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 Read More
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The white-chinned petrel (Procellaria aequinoctialis) is an abundat, widespread petrel breeding in tussock grassland at sub-Antarctic islands. Over the last decade it has been killed in large numbers in temperate and sub-tropical longline fisheries. However, no data are available on the global population status. We assessed the status of white-chinned petrels at Bird Island, South Georgia by Read More
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A bottom trawl survey was conducted in the northern half of the South African EEZ around the Prince Edward Islands in April 2001. Due to the paucity of bathymetric data, it was not possible to design a statistically rigid survey, consequently this first survey is regarded as a pilot study to ascertain the feasibility of conducting future trawl surveys, and to collect relevant data to aid in Read More
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At its last meeting, WG-FSA noted a declining trend in the mean lengths of toothfish caught around South Georgia and Shag Rocks over the period 1995 – 1999. We re-analysed the mean lengths of fish taken on individual longline sets from which length frequencies were sampled by observers and found the same declines in mean lengths for the period 1997 – 1999 as previously noted by WG-FSA, but Read More
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