Hundreds of dead fish at Waterloo pond likely caused by natural circumstances: Expert

It was an alarming sight for residents in the north end of Waterloo last week as hundreds of fish washed up on the shores of a shallow neighbourhood pond.

The incident took place at a retention pond, a man-made feature used to store runoff and prevent flooding, near the intersection of Erbsville Road and Wideman Road.

The dead fish, a mix of small species, could be seen floating near the shoreline or washed up onto the land around the pond. To get an understanding of the situation, Dr. Mark Servos, a professor at the University of Waterloo, took a walk around the pond.

“It’s not unusual for very shallow ponds, like this one, to have winter kill,” he said. “Essentially, they’re so shallow that when you have the ice and snow cover, there’s respiration occurring, and the oxygen gets slowly depleted through the winter, and then the fish die.”

According to Servos, the fish could have died at any point during the winter, and its the thaw uncovering the dead fish that makes it look like the incident may have happened all at once.

Servos added that the signs he observed at the pond don’t point to a contaminated water source or pollutants, as you would expect to see dead mammals and plants.

All the same, Servos is reminding people to be thoughtful about what they’re releasing into local watersheds.

“When you spill oil on your driveway, when you wash things, when you do things in your yards and it goes down the drain, it is going into these environments, which ultimately ends up in the river,” he said . “It’s up to every single person to be careful what they’re doing with water and how they’re polluting the water.”

“It’s up to all of us to protect the environment.”

The pond has since been cleaned of most dead fish.