CCAMLR

Scales and whole otoliths were read for age determination of early stages of Notothenia rossii caught in Potter Cove, South Shetland Islands, in summer of years 2003-2006 and 2008. The sample was composed by blue phase fingerlings of 7-7.6 cm (TL) and age group 0 year and demersal young brown phase juveniles of 8.5-20.9 cm and predominant age groups 1-2 years. Counting of sclerites facilitated the interpretation of the rings, particularly in the central area of the scale. To clarify two issues of controversy in the literature: 1) we believe that the duration of the pelagic fingerling stage at sea is less than one year before migration to the demersal nearshore habitat; 2) the first well defined ring in scales corresponds to the first annulus, while a contiguous nearby ring is a secondary ring deposited after the first winter during the second year, attributable to a shift of habitat from pelagic to demersal. Our inferences, based on interpretation of the distinct sclerite structures that constitute the rings, are illustrated/supported by photographs. A von Bertalanffy growth curve was computed by combining age/length data of the juvenile phase of N. rossii from this and a previous study at Potter Cove, with literature data from the offshore adult population, resulting in the equation:

This paper summarized the chilean catch data for 1991. Especial emphasis is given to the analysis of haul-by-haul data and its use in understanding small scale spatial distribution of fishing grounds. The results show that the krill fishery in subarea 48.1 is particularly intense near CEMP sites. Other uses of haul-by-haul data are suggestted.

Length composition of krill in diurnal and night hauls of FV Lepus, off S. Orkneys in January and February 1991, generally show similar pattern. The proportion of bigger individuals of krill in night hauls was slightly higher than within diurnal hauls. CPUE values in February were higher than those in January. No larval fish were recorded in krill catches. Only few specimens of Electrona antarctica (of length range 53 - 103 mm) were found in some night hauls.

Four Polish commercial trawlers participated in the krill fishery in 1990/91 season on the fishing grounds in statistical Sub-areas 48.2 and 48.3. In total 9 333.7 tonnes of krill were harvested. As the fishery data were not fully analysed yet no clear trends in catch-per-unit-effort for different fishing grounds during the season could be detected.

Krill swarms were recorded acoustically along a 2340 Nm of the ice edge between Elephant Island and South Orkney Islands. Depth distributions and migration pattern were different for the three distinguished regions. It has been sugested that physical factors are the most important in both :horizontal and vertical krill distributions.

Midwater trawl catchability is variable depending both on fishing object behaviour and distributional pattern end trawl parameters. Data on trawl catchability distribution parameters and krill distributional pattern in the surveyed area enable to increase reliability of the biomass estimates.
Comparative analysis for catchability of fishery midwater trawls and small research trawls, when Isaaks-Kidd trawl was taken as an example, proved the latters not to be suitable for krill biomass estimation using method of trawling surveys on abundance. Small research trawls were found to have high catchability variations in the surveyed ground and the biomass estimates were characterized by high relative error.
Standard methods of trawling survey on krill abundance should be worked out. Optimum construction of midwater trawl can be selected on the base of mathematical modelling using models of the fishing trawl statistical theory and conducting hydroacoustic studies of trawl catchability properties. Selection of trawl construction should include studies on estimation of krill total exemption.