CCAMLR

This paper summarises seabird bycatch during the fourth year (July 1999-June 2000) of sanctioned longline fishing for Patagonian toothfish Dissostichus eleginoides in the Exclusive Economic Zone around South Africa's Prince Edward Islands. Data were obtained from fishery observers aboard all 11 sanctioned fishing trips. Fishing effort was 7.4 million hooks, a 45% increase on the number of hooks set in 1998199. Observers reported 268 birds of six species killed. White-chinned Petrels Procellaria aequinoctialis predominated (92.2%), followed by Eastern Yellow-nosed Mollymawks Thalassarche [chlororhynchos] bassi (3.5%), Grey Pretrels P. cinerea (l.8%), Grey-headed Mollymawks Thalassarche chrysostoma (1.5%) and giant petrels Macronectes spp. (1.1%). Average seabird bycatch rate by sanctioned vessels was 0.036 birds per 1 000 hooks, more than double that reported in 1998/99, but still considerably less than that reported in either 1996/97 or 1997/98. The absolute number of birds killed increased more than threefold compared to 1998/99 due to the marked increase in fishing effort.
Variance in bird bycatch rates among trips ranged from 0.000 to 0.142 birds killed per 1 000 hooks. Birds were killed on 7.7% of sets, with most (68%) birds killed on only 49 sets that had multiple casualties (2.8% of sets). As in previous years, much of the variance could be explained in terms of fishing season (higher bycatch rate in summer), time of setting (higher during the day), and distance from the Prince Edward Islands (higher within 200 km of the islands).

We tested the efficacy of a Mustad underwater setting funnel to reduce seabird bycatch in a demersal longline fishery for Patagonian toothfish Dissostichus eleginoides. The funnel, which deploys the longline 1-2 m beneath the sea surface, was used on 52% of 1714 sets (total effort 5.12 million hooks) over a two-year period. There was no evidence for lower catches or significantly higher bait loss on sets through the funnel. Overall bird bycatch rate was low (0.022 birds per 1000 hooks), and was dominated by White-chinned Petrels Procellaria aequinoctialis (88% of the 114 birds killed). Bycatch rate was three times lower when the funnel was used both by day and at night. Daytime catch rates with the funnel were less than those attained during night sets without the funnel. Underwater setting offers a significant reduction in seabird mortality and could increase fishing efficiency by allowing daytime setting. However, small numbers of albatrosses were caught during daytime sets with the funnel, and its use for daytime sets should be closely monitored.

Historical information is assessed on the distribution of spawning and larval mackerel icefish within subarea 48.3 (South Georgia). This is considered alongside other new data from commercial fisheries and research surveys. It is concluded that there is strong evidence for inshore spawning during April within and close to the bays on the north side of the island. Some spawning at much lower intensity almost certainly occurs over much of the shelf although the intensity appears to be small in comparison with inshore spawning. There is some evidence for spawning at Shag Rocks although the precise location is unknown and there are indications that there may be a second limited spawning season in October although the evidence is weak.

A tagging programme for toothfish (Dissostichus eleginoides)w as undertaken around South Georgia during early 2000. Details of the programme are given. A total of 359 toothfish were tagged during a trawl survey on the Shag Rocks shelf and a further 135 were tagged on the continental slope around South Georgia and Shag Rocks. The programme has been advertised widely amongst industrial fishermen operating in the region.

To undertake the 'ecosystem approach' to fisheries management recommended by CCAMLR, an understanding of the trophic relationships of exploited species is vital. Toothfish, (Dissostichus eleginoides), represents an important target species for fisheries not only in the study area around South Georgia (CCAMLR Sub-area 48.3), but also in other CCAMLR areas. To improve the knowledge on the trophic relationships of this species, stomach analyses were performed on individuals caught during the toothfish pot fishery trials undertaken in the area during the period March to May 2000. 3,640 individuals were examined and their stomach contents identified. The proportion of individuals found with empty stomachs was greatly reduced in fish caught using pots rather than longlines, increasing sample sizes. This was hypothesised to result from fish caught in pots suffering reduced levels of trauma. The most common prey item for fish caught using pots was prawns. This prey category was localised in location and depth. However prawns were not common in the stomachs of fish caught from this location using longlines. The next most common prey category was fish, as found in previous studies of this species. This confirms that D. eleginoides s an opportunistic carnivore, whose feeding habits vary dependent on the availability of food items as well as Factors such as depth.

Trials of a method of fishing for toothfish using pots were undertaken by FV Argos Georgia from March to May 2000. A significant bycatch of crabs was encountered. Paralomis spinosissima occurred in shallow water, generally shallower than 800m. P. anamerae, which has not been reported for this area previously, had an intermediate depth distribution from 400 – 800m. P. formosa was present in shallow waters but reached much higher catch levels (and, presumably, densities) between 800 and 1400m. There were some differences in catch rate5 between areas, with lowest catch rates being encountered between Shag Rocks and South Georgia, and highest for P. formosa in deep water north of South Georgia. Few crabs (3% of P. spinosissima and 10.5% of P. .formosa) were males above the legal size limit and could be retained. All other crabs were discarded. Mortality rates estimated from re-immersion experiments indicated that about 10% of apparently lively discarded crabs would die.

During the period March to May 2000, the UK undertook trials of a pot fishing method to catch D. eleginoides around South Georgia (Sub-area 48.3). This method has the potential to minimise, or eliminate, incidental bird mortality when compared to the standard longline method. This paper describes the trial, the results, and discusses the commercial viability of this fishing method for toothfish fisheries in the CCAMLR area. While the method successfully caught D. eleginoides, there was a large bycatch of crab species. The catch rate of toothfish was notably lower than that achieved in the longline fishery. Importantly, the use of pots eliminated bird bycatch. To capitalise on this feature, there is a need to improve the commercial viability of the method and minimise the quantity of bycatch. A number of potential changes are suggested to this end.

Morphological information is given on specimens of Raja georgiana that were caught during a demersal trawl survey in Subarea 48.3, South Georgia. It is concluded that, in spite of allometric growth, proportional measurements are best referenced to total length rather than disc width. Additional biological information is given: total mass=0.00000646x(total length)3.06. Based on data from male fish, they are thought to mature at about 800mm total length.

A survey was conducted by the UK around South Georgia and Shag Rocks, Subarea 48.3, from 11 January to 2 February 2000, using the FV Argos Galicia. The design followed similar surveys by the UK conducted throughout the late 1980s and 1990s. The swept area estimates of the standing stock of Champsocephalus gunnari were about 24,800 t. Estimates for other major species are given.