Reduced bycatch of red king crab ( Paralithodes camtschaticus) in the gillnet fishery for cod ( Gadus morhua) in northern Norway

Abstract

Bycatches of red king crab ( Paralithodes camtschaticus) in stationary fishing gears, especially gillnets, are a growing problem for inshore fishermen in northern Norway. Large bycatches of king crabs cause extra work for the fishermen and damage their gear and catch. In the cod ( Gadus morhua) gillnet fisheries, the problem could be solved by designing gillnets that float above the seabed (“norsel-mounted” nets). Norsel-mounted nets floating 0.5 m above the seabed were compared with standard nets in the Varangerfjord (eastern Finnmark) in three periods. In the first period crab catches were generally small and the norsel nets caught 52% fewer cod than standard nets; it was also shown that norsel nets needed more floats than standard nets to stand properly in the sea. By using extra flotation (rings) on certain of the norsel nets during the second period, bycatches of king crab were reduced to an acceptable level, with a catch per unit effort (CPUE) of 0.5 crabs compared with 3.0 crabs with standard placement. Norsel nets with extra floats caught 66% fewer cod than standard nets. During the third period, extra floats were used on both norsels and standard nets. Norsel nets had a CPUE of 0.7 crabs, standard nets 2.4 crabs; norsel nets caught 31% fewer cod than standard nets. In the second and third period norsel nets caught larger cod, thus the catch differences between net types were less in terms of weight. Additional data collected by three coastal fishing vessels operating under different conditions (area and bottom topography), showed that norsel nets fished about the same number of cod and 58% fewer king crab than standard nets. This study indicates that the gear configuration was capable of reducing the bycatch of red king crab. Reduction in fish catches was the largest in periods with poor fishery, and area and bottom conditions may have influenced the catchability of norsel nets to a greater degree than standard nets.