Residents have spotted an unusual number of dead fish up and down the Lake Ontario shoreline in Niagara-on-the-Lake this spring.
For resident Diane Miller, the sight in her backyard was both startling and upsetting as she discovered the lifeless fish along the water’s edge on May 6.
“It was a bit of a shock,” said Miller. “And then it was a little sad.”
Senior media spokesperson Gary Wheeler from the Ministry of the Environment, Conservation and Parks told The Lake Report the ministry took water samples on April 30 from Lake Ontario after a large number of dead fish were found in Mississauga.
Tests showed the fish die-offs, or fish kills, were not tied to water pollution, he said.
“The ministry has not had any recent reports of spills linked to fish die-offs in Lake Ontario,” wrote Wheeler in an email.
The Ministry of Natural Resources and Forestry said that the dead fish were identified as alewife, a member of the herring family. They are abundant in Lake Ontario.
“Large spring-time mortality events are common with this species in the Great Lakes,” wrote a spokesperson for the ministry in an email. “These events are natural and not indicative of a larger environmental or health crisis.”
“However, it is advisable to avoid direct contact with dead fish to prevent any potential health risks.”
Alewives usually live in deep, cold water, but in May and June, they move to shallow areas to lay eggs.
These fish die-offs happen when alewives swim from the cold, deep parts of Lake Ontario to the warmer, shallow areas to lay eggs.
If the weather changes quickly, like during a storm, cold water can rise to the surface and shock the fish.
After a long, cold winter, alewives are already weak, so the sudden temperature change can make them sick or kill them.
“Spawning takes a lot of energy and can be stressful,” the ministry wrote.
In the spring, these three stressors often occur for alewife at the same time.
Miller said she is not concerned about harm to herself or her family and thinks it’s likely from natural causes.
“We’re getting a lot of bird migration right now,” she said. “That’s nature.”
She said it would be reassuring if the municipality had confirmed it had checked with the right authorities and that there is nothing to worry about.
However, Miller said she wouldn’t expect the town to be responsible for cleaning up the fish.
What tends to happen, according to the Toronto and Region Conservation Authority’s website, is that the waves and currents help carry the dead fish back into the lake, and wildlife can swoop in to make the most of the unexpected food supply.
“It went away and then yesterday — it was quite warm — and I didn’t actually go right down to the water, but you could see a few floaters,” she said. “But the birds are certainly feeding.”
This kind of die-off has happened before, like in 2019, and looks the same this year, states the conservation authority’s website.
Miller moved into her home in 2020 and said she has never seen anything like this.
The Niagara Peninsula Conservation Authority declined to comment and said the Ministry of Natural Resources and Forestry would be better suited to answer questions about the die-offs.
But its beach conditions webpage does state that large numbers of dead fish in the water can increase the risk of illness or injury.
“Please be advised that there are always risks associated with swimming in natural bodies of water,” the webpage states, going on to say that changing conditions can raise bacteria levels.
When contacted about the beach webpage, the conservation authority said in an email: “Our ‘beach conditions’ page provides the public with general information related to potential environmental factors that affect water quality at our park beaches.”
“We have not made any assumptions or conclusions about the impact of the observed fish die-off on public health.”
To report dead fish, residents can contact the Ministry of Natural Resources and Forestry at 1-800-387-7011. Instructions on reporting fish die-offs are available at ontario.ca/page/dead-animals-or-fish-found-your-property.
