Organochlorine accumulation and stable isotope ratios in an Atlantic salmon ž Salmo salar/ population from the Baltic Sea

We investigated the organochlorine accumulation Ž p, p -DDE and ÝPCB. and stable isotope ratios ŽN and C. in a migrating salmon ŽSalmo salar. population in the Baltic Sea. 15N in the entire population ranged from 11.7 to 13.7‰ and 13C ranged from 22.0 to 19.6‰. In the entire population, 15N were weakly related to p, p -DDE and ÝPCB concentrations Žr 2 0.20 and 0.14, respectively.. However, lipid content was a better predictor of organochlorine ŽOC. concentrations Žr 2 0.48 and 0.50, respectively.. Lipid adjusted ÝPCB concentrations were not related to 15N, and lipid adjusted p, p -DDE concentrations were only weakly related Žr 2 0.12.. We divided the salmon population into three groups representing reproductive strategies: small males 5 kg ŽSM.; large males 5 kg ŽLM.; and females ŽF.. 15N varied between the three reproductive strategies. The mean 15N for SM was 12.7 0.3‰, for F was 12.9 0.3‰, and for LM equalled 13.2 0.3‰. Lipid adjusted OC concentrations differed between the three reproductive strategies, with the females having the highest concentrations. We conclude that the 15N varied between reproductive strategies indicating differences in prey choice, but the lipid content was better able to predict OC concentrations than the trophic position of the salmon.