Size selection of Antarctic krill (Euphausia superba) in a commersial codend and trawl body

Abstract

During fishing, many fish species are able to avoid the net walls of the trawl body and so the majority of size selection occurs in the codend of the net. Antarctic krill (Euphausia superba) are regarded as true planktonic organisms passively drifting with currents, but they also display self-locomotion by active swimming. There is a lack of knowledge regarding the behavior of krill during the fishing process, and extrapolating results obtained for other species to krill is of limited value. In the case of krill, it is largely unknown to what extent the codend versus the trawl body contributes to the size selection process. The current study aims to quantify the size selection of krill in a commercially applied codend during experimental fishing. Combining these results with a model for full trawl size selectivity it was possible to provide an insight to the size selection process in the trawl body. Specifically, the study applied a two-step approach by first estimating the size selectivity of a commercial codend and second used the codend size selectivity obtained in this study to estimate the trawl body size selectivity of a commercial trawl based on entire trawl-selectivity obtained in a previous study. The results of this two-step analysis revealed that the trawl body contributes significantly to the total size selection process, demonstrating that size selectivity of Antarctic krill in commercial trawls is affected by both the trawl body and the codend.

Size selection of Antarctic krill (Euphausia superba) in a commersial codend and trawl body