FISH BEHAVIOR STUDIES AS AN AID TO IMPROVED LONGLINE HOOK DESIGN

The responses of cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.) to baited hooks were analysed to determine behaviour patterns which could form the basis for improved longline hook design. The most important behaviour pattern observed for successful hooking of fish was when the fish accelerated rapidly with the baited hook in its mouth (termed "rush" behaviour). A hypothesis for hook design was formed, proposing that a longline hook with its point towards the line of pull would catch more fish than a typical Atlantic longline hook with its point parallel to the line of pull. Two experimental hooks conforming to this hypothesis were compared with a standard hook in fishing experiments. Altogether 19 500 hooks were fished. One experimental hook caught significantly (P < 0.01 and P < 0.001) more cod than the standard hook in two fishing experiments, with insignificant results in the third. It also caught significantly more haddock (P < 0.01). The other experimental hook also caught significantly more cod and haddock than the standard hook (P < 0.001 and P < 0.01, respectively). Improved catch rates ranging from 10 to 33% were experienced. © 1990.