CCAMLR

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.