Continuous variation in the pattern of marine v. freshwater foraging in brown trout Salmo trutta L. from Loch Lomond, Scotland
Carbon stable-isotope analysis showed that individual brown trout Salmo trutta in Loch Lomond adopted strategies intermediate to that of freshwater residency or anadromy, suggesting either repeated movement between freshwater and marine environments, or estuarine residency. Carbon stable-isotope (13C) values from Loch Lomond brown trout muscle tissue ranged from those indicative of assimilation of purely freshwater-derived carbon to those reflecting significant utilization of marine-derived carbon. A single isotope, two-source mixing model indicated that, on average, marine C made a 33% contribution to the muscle tissue C of Loch Lomond brown trout. Nitrogen stable isotope, 15N, but not 13C was correlated with fork length suggesting that larger fish were feeding at a higher trophic level but that marine feeding was not indicated by larger body size. These results are discussed with reference to migration patterns in other species.
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Document Type: Regular Paper
Scottish Centre for Ecology and the Natural Environment, Institute of Biomedical and Life Sciences, Glasgow University, Rowardennan, Glasgow G63 0AW, U.K.
Scottish Natural Heritage, Caspian House, Clydebank Business Park, Clydebank, Glasgow G81 2NR, U.K.
Publication date: 2008-07-01