Th-303B-10
Annual and Ontogenetic Variation in the Diet of Lake Trout (Salvelinus namaycush) Using Stable Isotope Mixing Model

Thursday, August 21, 2014: 11:50 AM
303B (Centre des congrès de Québec // Québec City Convention Centre)
Lingbo Li , Fisheries Centre, The University of British Columbia, Vancouver, BC, Canada
Paul J. Blanchfield , Experimental Lakes Area, Fisheries and Oceans Canada, Winnipeg, MB, Canada
Stomach contents have long been used to obtain fish diets. However, for small lakes, this lethal method may significantly influence the population of the sampled fish and alter the whole lake ecosystem. Here we apply the stable isotope mixing models, based on nonlethal samples such as fin clips, to reconstruct the diet composition of lake trout in Lake 373 in Experimental Lakes Area, Ontario, Canada. We applied δ15 N and δ13 C analyses for the whole lake from plants to the top predator lake trout.  Based on fin clip samples during 2007 and 2012, we find that δ15 N value of lake trout increases as a function of fish length. Lacking covariance in δ15 N of lake trout and minnows may suggest no large changes in δ15 N signatures at the base of the lake and no large anthropogenic nutrient inputs during this time period. We model lake trout diets and discuss the difference between years and between body size classes.  Application of Bayesian mixing model to stable isotope analysis, using nonlethal samples, provides an excellent tool to estimate fish diets.