Reduced Catch of Under-Sized Cod (Gadus morhua) in Longlining by Using Artificial Bait

Abstract

Three sizes of artificial bait incorporating shrimp flavour into polyurethane foam were compared with natural shrimp bait of the size used in commercial longlining. Fishing trials were conducted during the spring fishery for Atlantic cod (Gadus morhua) off the coast of Northern Norway. The small artificial bait gave almost the same catch rate as natural shrimp bait, whereas artificial baits of larger sizes compared poorly. The length distribution of the catch was influenced by both bait type and bait size. Fewer small cod were caught on the artificial baits. There was no difference in the number of large cod. Mean cod length was therefore higher on the artificial baits and increasing the artificial bait size accentuated the difference. These effects are explained by different preferences with regard to prey species and size between small and large cod. The size selective effects of bait type and bait size are discussed in relation to conservation aspects.