Thousands of dead fish are blanketing the Belle River near Lake St. Clair.

Fish began floating to the surface near the island between West Belle River Road and Lalonde Street, near Belle River High School.

The Essex Region Conservation Authority suspects storm runoff, including sewage that bypassed treatment, from Monday’s record rainfall is to blame.

ERCA conducts water sampling on Wednesday’s along the Belle River, but results from this week are not back, yet.

Lakeshore Mayor Tom Bain and ERCA both started receiving calls Thursday night.

By Friday, thousands of fish could be seen floating on the river.

"Thousands of small shad fish dead floating on the water," Bain said. "They're real tiny. The size of a gold fish and then larger fish such as carp and catfish are all floating on the surface alive trying to get oxygen."

Bain said the Essex Region Conservation Authority told him another factor for the deaths could be a sudden change in the water  temperature during the rain storm. 

ERCA tells CBC News it's possible the sewage and bacteria in the water deprived the smaller fish of oxygen, which in turn did the same to larger fish.