‘Likely natural’: Cause of dozens of dead fish in Port Franks investigated

Provincial and local authorities say the cause of dozens of dead fish floating in the Ausable River in Port Franks, Ont., and Lake Huron is likely natural.

Over the weekend, residents living on or near the river began posting on social media pictures of the fish floating up against docks or onto beaches.

The local municipality, Lambton Shores, notified residents that it was aware of a “number of dead fish” reported in the Port Franks area.

Following these reports, staff from the Ausable Bayfield Conservation Authority (ABCA) and Ministry of the Environment, Conservation and Parks investigated the area on Monday to determine the source of the fish die-off.

In a statement to Global News, the ministry says it did not identify any spills or contaminants that could have contributed to the die-off.

“Based on how widespread the dead fish have been located, both in the Ausable River and along the shores of Lake Huron, the die-off is likely the result of naturally occurring conditions,” ministry spokesperson Lindsay Davidson said.

Kari Jean, the aquatic biologist with the ABCA, tells Global News she agrees with the ministry that the source of the die-off was likely natural. While the exact reasons for the natural die-off have not been confirmed, Jean says a likely explanation is volatile weather.

“There has been a lot of rain, which contributes to runoff and lots of sediment getting into the river, which fish don’t like,” said Jean.

She explained that high volumes of sediment stirred up by the rain could deplete the dissolved oxygen available to the fish and suffocate them.

While a die-off in fish can sometimes be attributed to a virus, Jean says that is usually only the case if the fish dying are the same species.

“From what I saw, there were different sizes, ages and types of fish part of the investigation,” said Jean. “It was not targeted to any one species.”

Despite the large number of fish dying, Jean says there is nothing to indicate the waters of the Ausable River in Port Franks or Lake Huron are unsafe for swimmers or boaters.

Regarding preventive measures, Jean says the conservation authority will continue planting trees, bushes and other habitable wetland vegetation along shorelines to slow down rain entering the waterways and instead have it soak into the ground.

“We need to continue to do more work to protect the habitat these fish need and to reduce the potential for harmful impacts,” added Jean.