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

We investigated the organochlorine accumulation (p,p′-DDE and ∑PCB) and stable isotope ratios (N and C) in a migrating salmon (Salmo 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 ∑PCB concentrations (r2=0.20 and 0.14, respectively). However, lipid content was a better predictor of organochlorine (OC) concentrations (r2=0.48 and 0.50, respectively). Lipid adjusted ∑PCB concentrations were not related to ∂15N, and lipid adjusted p,p′-DDE concentrations were only weakly related (r2=0.12). We divided the salmon population into three groups representing reproductive strategies: small males <5 kg (SM); large males >5 kg (LM); and females (F). ∂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.