Chemicals are likely to blame for the feminization of fish in two southern Alberta rivers, say researchers at the University of Calgary.
The scientists analyzed water in the Red Deer and Oldman rivers south of Calgary, studying the effects of about two dozen contaminants on a common minnow, the longnose dace.
In almost every population they studied, males had elevated levels of a protein normally only found in females producing eggs.
"Most notably, we saw a significant increase in a specific protein marker for the presence of compounds with estrogen-like activity in areas downstream — south of Fort Macleod and Lethbridge," said study co-author Hamid Habibi, director of the Institute of Environmental Toxicology at the University of Calgary.
Compounds detected in the water included synthetic estrogens, which are commonly present in birth control pills and hormone therapy drugs.
The contaminants could be naturally occurring, or they could be left over from inadequate wastewater treatment systems, Habibi said.
'If these animals are exposed at a very early stage, in fact there is evidence that it could alter the sex development.' —Hamid Habibi, study co-author
The study also revealed that females make up 85 per cent of the minnow population downstream from Fort Macleod and Lethbridge.
Upstream of those communities, only 55 per cent of the population is female — a more normal sex ratio, Habibi said.
This could indicate that chemicals in the river are causing the fish to change sex, he said.
"If these animals are exposed at very early stages, in fact there is evidence it could alter the sex development. The estrogenetic compound in fish could make a male fish develop into a female fish."
"Unfortunately, we don't have a specific marker in fish to determine whether sex reversal has taken place or not," he added.
The two rivers, which are part of South Saskatchewan river basin, were also contaminated with bisphenol A — a chemical used in making plastics — as well as natural and synthetic steroids. Those could be the byproducts of agriculture and cattle farming, according to the study.
"The Oldman River goes through a so-called feedlot alley," said Habibi.
The harmful effects of these pollutants on native fish will likely get worse over time, said study co-author Lee Jackson, a wastewater treatment expert who works with the City of Calgary to improve procedures at its newest treatment plant.
"What is unique about our study is the huge geographical area we covered," Jackson said. "We found that chemicals — man-made and naturally occurring — which have the potential to harm fish were present along approximately 600 kilometres of river."
The research, part of a larger study on chemicals in Canadian river basins, is being published in the next edition of the journal Environmental Toxicology and Chemistry.