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On the potential impact of harbour seal predation on the cod population in the eastern North Sea
Hansen, B.J.L.; Harding, K.C. (2006). On the potential impact of harbour seal predation on the cod population in the eastern North Sea. J. Sea Res. 56(4): 329-337. dx.doi.org/10.1016/j.seares.2006.06.004
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101, more
Peer reviewed article  

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Keywords
    Age composition; Fisheries; Population dynamics; Predation; Predator prey interactions; Gadus morhua Linnaeus, 1758 [WoRMS]; Phoca vitulina Linnaeus, 1758 [WoRMS]; ANE, Kattegat [Marine Regions]; ANE, Skagerrak [Marine Regions]; Marine

Authors  Top 
  • Hansen, B.J.L.
  • Harding, K.C.

Abstract
    Increasing Scandinavian harbour seal populations during the last decades coincide in time with the collapse of the cod fishery. Assumptions of a causal relationship have led to claims favouring re-introduction of seal hunting. Proposals for 'adaptive management' often assume that decimating seal populations will automatically favour the fishery. This argument presupposes seal predation to be sufficiently large to have a measurable impact on the fish population. The potential magnitude of the cod-seal interaction was analysed using data on harbour seal abundance, feeding habits and compiled information on cod life history and cod landing statistics. A size-structured life history matrix for the cod population was applied and the size-specific prey preferences of harbour seals were taken into account. Estimated seal predation was small compared to both the landings by the fishery, and to minimum estimates of the total cod population. Furthermore, since the size classes of cod targeted by seals have low reproductive values, the impact of seal predation on cod production will be further reduced. Our analyses suggest harbour seals have a negligible impact on the cod fishery.

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