Mixed fisheries management: protecting the weakest link

Abstract

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 métiers. 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 discarding.

High-grading and over-quota discarding in mixed fisheries

“…These results are in line with previous studies showing the adaptability of fishers in a mixed fishery to reallocate effort in space and time thereby optimizing their catch composition relative to the size of the quota (Poos et al 2010;Batsleer et al 2013). Our model results indicate that substantial high-grading may occur at the beginning of the year, long before quota are exhausted as a result of seasonal variation in the price of plaice.…”

“…Gillis et al 1995;Poos et al 2010;Batsleer et al 2013). Some simplifying assumptions, however, still remain.…”

“…Dynamic state variable models have been applied in a variety of fisheries to analyse vessel fishing behaviour (Gillis et al 1995;Poos et al 2010;Dowling et al 2012;Batsleer et al 2013). In such models, the optimal annual strategy of fishing vessels operating in fisheries under individual quotas and in a stochastic environment is evaluated.…”

Adaptive responses of tropical tuna purse-seiners under temporal regulations

“…Understanding both the incentives and behaviour of fishers is a crucial step towards designing management measures. Simulation analyses can help to evaluate possible fishers' responses before implementing management measures (Dorn 1998;Batsleer et al 2013). In this regard, the indicators used in this study can be used as input data to perform simulations.…”

Mixed fisheries management: Is the ban on discarding likely to promote more selective and fuel efficient fishing in the Dutch flatfish fishery?

“…This discard ban aims at stopping discarding for commercially valuable species, much like in other countries such as Norway (Diamond and Beukers-Stewart, 2011), Iceland (Arnason, 1995) and NewZealand (Annala,1996). If properly implemented and enforced, a discard ban could reduce discarding by encouraging the use of more selective gears and by forcing fishers to select fishing areas with lower discard catch rates (Condie et al, 2013;Batsleer et al, 2013). As the catch of undersized fish may not be completely avoided, a discard ban is expected to reduce the economic value of the landings for fisheries operating under catch quotas since part of the landings will consist of undersized fish that cannot be sold for human consumption but will likely be sold at a lower price for fish meal (Diamond and Beukers-Stewart, 2011;Buisman et al, 2013).…”