Researchers say that chemicals in two rivers in southern Alberta are likely causing feminisation of fish.
"The situation for native fish will likely get worse as the concentration of organic contaminants will become more concentrated as a response to climate change and the increase in human and animal populations," said Lee Jackson, executive director of Advancing Canadian Wastewater Assets.
The two rivers in question are: The Red Deer and Oldman rivers, located in southern Alberta, Canada.
The team found synthetic estrogens (birth control pill compounds and hormone therapy drugs), bisphenol A, a chemical used in making plastics.
There were also certain types of natural and synthetic steroids that are by-products of agricultural run-off and cattle farming.
The analysis showed elevated levels of a protein, hepatic vitellogenin, in male minnow, longnose dace fishes. This protein is normally only found in the blood of females and is used by females to produce eggs.
"Our results showed females make up 85 per cent of the population of longnose dace. In the upstream locations, females comprise 55 per cent of the population," says Habibi, who is also the director of the newly established Institute of Environmental Toxicology at the University of Calgary.
The find is published in the journal Environmental Toxicology and Chemistry.