Size-selective effects of increasing bait size by using an inedible body on longline hooks

Abstract

Larger minimum legal sizes and other regulations recently enforced in the Norwegian fisheries for gadoids have increased the need to improve the selectivity of fishing gear. In longlining, bait size is regarded as the most important factor affecting size selectivity, and the potential for improving the size selectivity of longlines by using a plastic body attached to the hook shank, causing the bait to appear larger, was therefore tested on pelagic longlines for haddock ( Melanogrammus aeglefinus), and on bottom longlines for torsk ( Brosme brosme) and ling ( Molva molva). The results showed that baited hooks with a plastic body attached to the shank caught a lower proportion of under-sized haddock (under 44 cm) than hooks with bait only. Catch rates and mean lengths of torsk and ling were similar for the two types of hook, indicating that an inedible body in combination with bait did not affect catching efficiency or size selectivity for these fish. In pelagic longlining, the baited hooks are more readily seen than hooks set on the seabed, and the differences observed may be explained by better visibility rather than in terms of species differences in behaviour.