Abstract

An isolated population of beluga whales (Delphinapterus leucas) has inhabited the St. Lawrence Estuary for over 8,000 years. This population of whales is sharing the Great Lakes/St. Lawrence (GL/SL) ecosystem with numerous species including humans. Since the first settlements of Europeans along the St. Lawrence shores, this co-habitation has been often challenging for this population of white whales. These whales were almost completely overharvested to extirpation, first for oil, and then because they were thought to compete with commercial fisheries. Despite the prohibition of hunting over 30 years ago, this population, now estimated to be composed of 900 individuals (representing 12% of estimated historical levels), has not shown any sign of recovery. Limiting factors that could account for this include: habitat degradation, anthropogenic disturbance, reduction of food resources and exposure to immunosuppressive, carcinogenic and endocrine-disrupting contaminants such as PCBs, HAPs and PBDEs. An ongoing pathology program, established in 1983, has documented causes of mortality in this population. Infectious diseases, such as verminous pneumonia, accounted for the death of one third of all beluga. Cancers were detected in 22% of the mature adult beluga (> 19 years old). Dystocia and postpartum complications were the cause of death of 19% of the mature adult females examined. Parturition-associated complications, as well as mortality of calves, have increased recently and may be the cause of the recent decrease in the size of this population. Exposure to contaminants has been proposed as a potential explanation for the unusually high occurrence of some of the pathological conditions observed in this population. This mortality monitoring program helped to raise awareness on the potential effects of human activities on the diversity of the GL/SL ecosystem; the beluga becoming a symbol of the detrimental consequences of industrialization on wildlife. Several mitigation measures have been instituted over the years, including the designation of a marine protection area and initiatives of GL/SL water quality improvement and contaminants reduction. These initiatives resulted in a decrease in the exposure of beluga to some potentially deleterious contaminants, such as PAH from aluminum smelters. Global climatic changes and local industrial developments are also seen as a source of uncertainties for this population of arctic odontocetes. Despite an often difficult co-habitation with us, beluga whales have been able to survive in the GL/SL ecosystem. The future of this endangered population will be highly dependent of the anthropogenically driven alterations of the GL/SL ecosystem.

* Presenting author