A study by the University of Ottawa claims that the Moses-Saunders dam on the St Lawrence river, between the US and Canada, appears to make cancer-causing pollutants collect above the dam. More than 50% of the bottom-feeding fish there have cancerous tumours around their mouths where they rub against chemicals in the river sediment.

The study, by 35 professors and 50 students, has put together the first picture of the biology, water quality and human communities along the Upper St Lawrence between Montreal and Lake Ontario. The scientists and their students caught 75,000 fish over three years of netting. They measured and released most of them but saved a few for laboratory analysis in the C$2.2M study.

It is claimed that the Moses-Saunders dam has changed the flow of water upstream so that whole communities of water plants, bottom-dwelling creatures and fish have been destroyed. The water level in the river has been raised since 1958 to facilitate navigation.

The dam is owned jointly by Ontario Hydro and the New York Power Authority. The New York Power Authority owns the 1860MW Robert Moses hydro station, located on the US part of the dam, while the 1860MW RH Saunders plant, located on the Canadian side, is owned by Ontario Hydro. Each utility owns 16 turbines and shares the flow of the river equally. The site develops a head of 27.4m.

The findings of the study may hamper attempts to relicense the hydro power dam when its current licence expires in 2003.

Beauharnois dam, located further downstream, was also named by the study as having a detrimental impact on fish habitat in the river.