A method to evaluate selection of Antarctic krill in towed fishing gears

The pelagic trawlers involved in the fishery for Antarctic krill (Euphausia superba) apply different trawl designs. Very little information exists on the size selectivity of E. superba. Size selectivity describes a given trawls designs ability to catch different sizes of a population and is valuable information for the management of harvested marine stocks. Size selectivity data is traditionally collected during timely and costly fishing experiments in the field where one design is tested at the time. FISHSELECT is developed as an alternative method, and is based on thorough measurements of the morphology of the species in quest and the shapes of the relevant mesh types, to predict the size selectivity by mathematical modeling. After making modifications with the procedures in FISHSELECT to parameterize morphology, the method proved applicable to determine size selectivity in different trawl designs for E. superba. We present design guides that predict the basic selective properties for E. superba in all relevant sizes of diamond meshes 5 - 40 mm and the opening angles of 10 - 90 degrees. Our predictions are based on the species morphology only, and do not take into account potential behavioral effects. Finally, we discuss how our result can be utilized for management purposes to increase the understanding of the catching process of E. superba and the selective properties in different fishing gear.