Speaker: Vanessa Trijoulet


Date: Dec 14




"It has been several decades that groundfish stocks have decreased around the UK. Meanwhile, grey seal population has increased. This has created a controversy between fishers and conservationists regarding the role grey seals have played in the stock depletion. Currently, opinions are still divided, and further studies need to be done to mitigate these conflicts.

A bioeconomic model able to quantify the economic impact of grey seal predation on West of Scotland demersal fisheries for cod, haddock and whiting was developed. The biological part of the model accounts for seal predation and fishing catches and is linked to an economic model accounting for fleet revenues and costs.


Three scenarios are tested. The “status quo F” model assesses seal predation impacts on fleet revenues at the biological equilibrium. Two dynamic models are also studied to determine seal impacts when fleet behaviour is considered: the maximum economic yield scenario (MEY) where the fishery net profit is maximized and the bioeconomic equilibrium (BE) model where the profits are dissipated in the long-run.


Cod is the fish the most impacted by grey seal predation so is the key stock in evaluating fishery effects. While the biological impacts can be important, seal predation is not economically important at the fishery level but some fleets are more sensitive than others. The large whitefish trawlers are likely to be the only fleet that could benefit from a reduction in grey seal predation. The following increase in its revenues would be certainly improved by fishery regulations."