Gear selectivity and bycatch reduction in the Norwegian Red King Crab (Paralithodes camtschaticus) fishery. A study on size-selective performances of different escape openings

Abstract

This thesis aims to investigate ways to improve the size selective performances of the fishing gear that is currently employed in the fishery for Red King Crab, Paralithodes camtschaticus, in Northern Norway. High bycatch rates of undersized crabs are a source of concern since these individuals have to be sorted out and dicarded into the sea, a procedure that increases the risk for injuries and unaccounted mortality. Bycatch-related problems and knowlegde of king crabs’ behavior in relation to fishing gear are explained in detail. Escape vents which are implemented into the side panels of the presently used rectangular pots can faciliate the egress of captured sublegal-sized animals while the pot is on the seafloor and are regarded as a commom tool to reduce their unintentional retention. Comparative fishing trials have been carried out during February and March 2016 in the Varangerfjord in order to compare the catch compositions of traps equipped with escape vents of different shapes and sizes. Their abilities to sort out undersized crabs while keeping legal-sized ones inside the gear have been analysed by running Kruskal-Wallis H-tests. The results of these experiments did not reveal one of the tested escape opnenings to be superior to the others in all terms, though certain tendencies are recognisable.