Challenges for the assessment of the UK stock of European eel, Anguilla anguilla

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The European eel stock is in a severely depleted state, and ICES continues to advise that it is outside safe biological limits. The European Commission's Eel Recovery Plan aims to restore the spawning stock, and a management target has been set as 40% of historic, potential silver eel emigration. Responsibility for selecting and effecting management actions has been devolved to Member States. A pseudo-stock/recruitment relationship has been hypothesized for the stock as a whole. However, our present inability to link maturing silver eel escapement with subsequent recruitment at management units relevant to national boundaries (e.g. river basins or districts), and the limited distribution of fisheries around the UK, precludes the use of conventional stock assessment methods. Furthermore, there is a paucity of historic and even recent data on eel populations in nearly all UK rivers, from which we could directly set management targets, assess present-day compliance and, if necessary, select from various management actions to restore silver eel escapement. In light of these challenges, one option being pursued is the development and application of habitat-based life history production models for eels. This paper outlines the challenges associated with this approach and describes recent developments for the proposed management of eels in the UK.