Modelling fishers' response to discard prevention strategies: the case of the North Sea saithe fishery

Designing effective management plans requires understanding fishers’ behaviour under that plan, because fishers change their behaviour in response to economic and management incentives, which in turn will lead to different fishery outcomes. This study presents a modelling framework for management strategy evaluations which takes into account the response of fishers to management schemes. Based on the upcoming discard ban, two discard prevention strategies were tested for the North Sea saithe fishery, where fleet segments have either no or a generally lowquota for cod. Costs and benefits were assessed under the current management, a non-flexible system, where fleet segments had to stop fishing once the cod quota was reached and a flexible system where quota of saithe could be used to cover over-quota catch of cod at a ratio 1:5. The flexible scenario was beneficial both in protecting the North Sea saithe and cod stock and in increasing net profits of fleet segments in the long term. The avoidance behaviour of fleet segments to over-quota catch led to a high SSB level of saithe and cod in the long term, ensuring high long-term catches and profits. A non-flexible scenario had a negative impact on the saithe stock, because mainly juvenile saithe before spawning were caught reducing the spawning-stock biomass in the longer term. A non-flexible scenario was costly in terms of up to 29% lower net profits for individual fleet segments generating little economic incentive to be compliant.