A modelling-based perspective on the past, present, and future polychlorinated biphenyl contamination of the St. Lawrence beluga whale (Delphinapterus leucas) population

Individual- and population-based models are presented that provide quantitative assessments of the accumulation of persistent organic pollutants over the lifetime of the beluga whale (Delphinapterus leucas) and consider all aspects of its life history. The models are used to examine the history of polychlorinated biphenyl (PCB) accumulation by the endangered St. Lawrence beluga population from 1950 to the present and to predict future trends based on likely contaminant loading scenarios. The hypothesis that migrating American eels (Anguilla rostrata) are a significant source of contaminants to the population is examined. The history of PCB exposure via the diet is reconstructed from existing data and from PCB profiles in dated sediment cores. The models adequately describe the effects of age, growth, sex, and reproductive activity on PCB concentrations in the beluga, and results show good agreement with observed concentrations when eels are included as 3% of the annual diet. PCB levels in the population appear to have peaked between 1967 and 1972. The model agrees with recent studies that have shown that PCB concentrations in the population are declining slowly.