Scientists are growing concerned after male fish displaying female traits were found recently in certain parts of the Grand River.

Mark Servos, Canada Research Chair in Water Quality at the University of Waterloo (UW), says “It’s clearly linked to the sewage treatment plant.”

The abnormal male fish were found to be carrying abnormally large eggs.

“The eggs are typically only seen microscopically but here at this site we can actually see the eggs visually with our eyes,” Servos says.

Researchers are placing cages of fish in the river, to see what effect the effluent in the water will have on them.

UW PhD student Meghan Fuzzen says “Something is happening, we’re just not exactly sure what that is.”

The number of abnormal males in the Grand River is among the highest compared to similar studies done in other parts of the world.

UW researcher Gerald Tetreault says “The environment downstream from those sewage treatment plants might be impacted just because of the pharmaceuticals and estrogens in birth control pills.”

The findings may be related to the sedentary nature of the fish being studied, but researchers say preliminary results show it may impact the viability of all fish.

“There is some less fertilization from the fish that are collected downstream from the sewage treatment than from at least above the city limits, they have a better success rate of fertilizing the eggs,” Fuzzen says.

Some species favoured by fishermen could also be affected, Tetreault adds.

“It’s the trout and the bass and the walleye that eat these little fish so that’s something we haven’t been able to look at yet.”

Officials with Waterloo Region say there’s no evidence of any problems with drinking water pulled from the river.

Thomas Schmidt, with the region’s environmental services department, says “We have a number of barriers in the plant that would remove these types of chemicals and we’ve actually done research to show that in many of them they are completely removed and some of them there are very, very small quantities left afterwards.”

Researchers hope to have some idea about what may be the water and what could be causing these conditions in the fish in a couple of years.