CCAMLR

Breeding wandering albatrosses Diomedea exulans at South Georgia have a relatively low level of potential risk of interaction with Patagonian toothfish Dissostichus eleginoides longline fisheries at South Georgia between late November through February and between late May and October. From March through mid-May birds of both sexes spend most of their time at sea over the South Georgia continental shelf in very similar areas to where the longline fishery operates and are therefore at serious risk from these fisheries at this time. We recommend that the South Georgia longline fishery for Dissostichus should be managed so as to avoid fishing between March and mid-May.

En este trabajo, se reunió la información de mortalidad incidental de aves marinas ocurridas en los buques argentinos y chilenos que operaron en la temporada de pesca del Dissostichus eleginoides en la subarea 48.3 entre el 1 de marzo y el 16 de mayo de 1995. Los datos tienen su origen en los informes de escala fina entregados por los capitanes de las naves a las autoridades pesqueras de ambos paises y en los informes presentados por los Observadores Científicos. De esta manera, se pudo evaluar cerca del 100 % de la mortalidad ocurrida durante la temporada. Se encontró una mortalidad total de 954 aves, cuyo 69% es Procelaria aequinoctialis, seguida por Phoebetria fusca ( 13%), Macronectes .giganteus (8%), Diomedea melanophris (4%)) Diomedea epomophora (3%) y Diomedea exulans (0,3%). También se registro un total de 537 aves capturadas durante los virados y liberadas vivas, entre las cuales dominaron Phoebetria fusca ( 61 %) y Macronectes giganteus ( 18 %). Se estudiaron las variables que podrían afectar esta mortalidad encontrándose que: 1) la distancia a las islas , 2) el ciclo lunar ( ya que la casi totalidad de los lances fueron nocturnos) 3) el uso de las lineas espantapájaros y 4) el tamaño de los anzuelos, son importantes fuentes de variación tanto en el análisis global BPUE por barco como en escala de lance por lance.

This paper presents a flexible structure for a general yield model, which provides flexibility for assessing the influence of different patterns of growth, natural mortality, spawning and fishing on the estimates of yield per recruit. Also, it can be used to evaluate the performance of a stock under a specified catch regime. The model uses an adaptive Runge-Kutta procedure to evaluate stock trajectories and catch rates over a simulation period. In particular, this procedure calculates catches over each year by integrating a set of differential equations which incorporate functions that specify the rate of change or magnitude of parameters, such as growth, mortality, age dependent selectivity and seasonal patterns in fishing mortality, at specified time intervals during the year. This general approach also includes an option for a stock to experience a known catch history before the constant catch regime is introduced.

A final report of scientific observations conducted aboard the Japanese krill fishing vessel Chiyo Maru No. 2 was presented to the first meeting of WG-EMM. The WG-EMM welcomed the report but noted that the results for reporting fish bycatch were not presented in CCAMLR's standard format. This manuscript presents a brief reanalysis of the bycatch data collected onboard the Chiyo Maru No. 2; means and variances are calculated according to the methods of Aitchison (1955) and Pennington (1983). In numbers, an average of about 20 fish were caught per ton of krill, and an average of about 23 fish were caught per hour of towing. In weight, an average of about 1.5 kg of fish were caught per ton of krill, and an average of about 2 kg of fish were caught per hour of towing. Confidence intervals for mean bycatch estimates are wide.

An age-length key was prepared for Champsocephalus gunnari from the Subarea 48.3, based on the readings of otoliths collected during the R/V Holmberg survey in February 1995. Small and medium sized fish (total length 12-34 cm) predominated in the samples at South Georgia, while larger specimens (>34 cm) were scarce. Age groups 1-5 and 2-4 were well represented at South Georgia and Shag Rocks respectively. At South Georgia, a good agreement between modes in the size distribution and mean length at age was found for age groups one and two. Mean lengths at age reported here for South Georgia are in line with previous results.

About 1300 stomach contents of the icefish Champsocepha1us gunnari caught in the Subarea 48.3 in February 1995, were analyzed using the frequency of occurrence (%) method. Krill (Euphausia superba) (58%) and the amphipod hyperiid Themisto gaudichaudii (55%) occurred similarly at South Georgia and constituted the main food. At Shag Rocks, T. gaudichaudii was the main prey item (52%), followed in importance by the mysid Thysanoessa sp. (35%) and krill (24%). The picture around SG was found to be similar to that observed in the E. Holmberg survey in February/March 1994: common levels of krill availability indicated by frequency of occurrence, but, on the other hand, high proportions of empty stomachs (also at Shag Rocks), close to the values reported for years of krill scarcity. While no krill aggregations were found in the South Georgia shelf during the Holmberg Cruise in Feb-March/1994, an acoustic survey carried out in the same area in March 1995 detected such aggregations. It is suggested that krill availability for C. gunnari around South Georgia in the 1995 summer season, was somewhat below the historical years of high abundance, but above than in 1994.