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Diseases of Beluga Whales in the Saint Lawrence Estuary
Bacteria, virus, parasites, and cancer are the most frequent causes of death and diseases of beluga whales living in the St. Lawrence Estuary. The tissues of these cetaceans are contaminated with high levels of industrial contaminants known to be carcinogenic and/or
immunosuppressive in every animal species where they have been tested. These facts have been recently reported by the Faculty of Veterinary Medicine at the University of Montreal in a
website that reveals the results of a series of
autopsies on beluga whales.
History of the Beluga
A small population of beluga whales (Delphinapterus leucas) estimated at 650 individuals is all that is left from the Arctic fauna of the last glaciation. This population counted 5,000 animals at the beginning of the century.
Thus, over 70 years, 90 % of this living record of the biological history of the North American continent
disappeared, which earned the beluga the status of endangered population from Government of Canada in 1980.
St. Lawrence Estuary
This population now permanently inhabits a marine Arctic microenvironment, which is a short segment of the St. Lawrence Estuary, centered
approximately on the mouth of the Saguenay River (see map).
Along the north shore of the Estuary, the icy Labrador current flows south-westward 300 meter deep, in the Laurentien channel (cold water is denser than warm water), in a direction that is opposite to that of the surface current.
At the level of Tadoussac, a small village of the north shore where the Saguenay river joins the Estuary, the Labrador current hits a huge, almost vertical, underwater wall. There, the depth of the Laurentien channel de-creases abruptly from 300 meters to 10 meters (arrow).
The icy water of the Labrador currents surfaces and creates a local Arctic marine environment while this
upwelling current brings into suspension an enormous amount of organic material from the bottom.
This material provides abundant food for plankton, which is eaten by fin whales, which are seasonal visitors to the area. Plankton is also eaten by dense populations of small fish. In turn, these become the prey of beluga and other marine animals, including seals.
St. Lawrence beluga whales are in a way prisoners of this short segment of the Estuary because of these unique ecological conditions and also because of the specialized physiological and morphological adaptations of the
The Estuary drains one of the most industrialized regions of the world which includes major industrial cities such as Chicago and Detroit, both
located on the Great Lakes.
Because of this downstream location, the St. Lawrence River has been contaminated for decades by industrial effluents. The St. Lawrence valley is also a place of extensive agriculture. Herbicides and fertilizers used by
modern agriculture also contribute to the pollutant load released in the Estuary.
From 1983 to 1998, nearly half (119) of the 246 beluga carcasses stranded in the St. Lawrence estuary have been examined in the postmortem room, at the College of Veterinary Medicine of Université de Montréal by veterinary pathologists. The postmortem examination has been coupled with the toxicological analysis of tissues.
Of the carcasses examined, 79% were considered to be preserved
adequately for diagnostic purposes. Seven-teen beluga (18 % of preserved
carcasses) died of cancer.
Cancer was observed in 27 % of examined adult animals from 1983 to 1998). In the western world, cancer causes 23 % of all deaths in humans, a percentage similar to that found in St. Lawrence beluga. Such a high
percentage had never been observed in any wild animal species, terrestrial or aquatic (with the important exception of fish).
The rate of cancer in Saint Lawrence beluga is also much higher than that observed in other cetaceans. Only 28 other cases of cancer have been reported in wild and captive cetaceans world-wide. Thus, cancers reported in Saint Lawrence beluga represent about half of all cancers reported in cetaceans world-wide.
In addition, some of the cancers affecting Saint Lawrence beluga, such as cancer of the small intestines, are rare in all mammals, including humans. Yet, seven of these cancers were observed in a population of 650 animals since 1983.
The evidence indicates that the beluga population is being exposed to a variety of industrial contaminants
including carcinogens and immunosuppressive heavy metals and
Anything that can be done to reduce the load of toxicity on these mammals would be of great benefit.
Rubin, President, Toronto Office, 52 Robert Hicks Dr., Toronto, Ontario Canada M2R 3R4 Tel: 416-650-1567 Fax: 416-650-1565
Bruce Small, Gen. Mgr., Research Office, #1661 Conc. 2, R.R.#3, Stouffville, Ontario L4A 7X4 Tel: 905-642-3082 Fax: 905-642-8867