Investigating patterns of straying and mixed stock exploitation of sea trout, Salmotrutta, in rivers sharing an estuary in south-west England

For effective management, information on the stock composition of a fishery is essential. Here, the utility of a resident trout, Salmontrutta L, microsatellite baseline to determine the origins of sea trout entering the rivers Tamar, Tavy and Lynher in south-west England is highlighted - all share a common estuary and have major runs of sea trout. There is a high degree of geographical structuring of the genetic variation in the baseline rivers. Testing with simulated and real data sets showed fish can be assigned to reporting group with a high degree of accuracy. Mixed stock analysis of >1000 sea trout showed that fish entering the Tamar and Tavy constituted mixed stocks. Significantly, in the Tamar, non-natal origin sea trout are restricted to the lower catchment. As well as providing insight into sea trout behaviour, this study also has important implications for the management of recreational rod and line fisheries.