Mixed fisheries management: protecting the weakest link

Batsleer, J.; Poos, J.J.; Marchal, P.; Vermard, Y.; Rijnsdorp, A.D.


North Sea cod Gadus morhua stock is outside safe biological limits, and total allowable catch (TAC) management has proved ineffective to rebuild the stock. The European Commission is considering the imposition of a discard ban to preserve vulnerable and economically important fish stocks. We explored the potential effects of a discard ban in mixed fisheries management using the French mixed fisheries in the Eastern English Channel as a model system. We examined in particular the performance of 2 different management scenarios: (1) individual quota management with a tolerance for discarding and (2) individual quota management in combination with a discard ban, using a dynamic state variable model. The model evaluates a time series of decisions taken by fishers to maximize profits within management constraints. Compliance to management was tested by applying an in-height varying fine for exceeding the quota. We then evaluated the consequences of individual cod quota in both scenarios with respect to over-quota discarding, spatial and temporal effort allocation and switching between m├ętiers. Individual quota management without a discard ban hardly influenced fishers' behaviour as they could fully utilise cod quota and continue fishing other species while discarding cod. In contrast, a discard ban forced fishers to reallocate effort to areas and weeks in which cod catch is low, at the expense of lower revenue. In general, a restrictive policy for individual quota for cod needs to be combined with a discard ban and a high fine (>20 times the sale price) to reduce over-quota discardin