City crews will begin cleaning up the hundreds of dead fish that are floating along the shores of High Park’s Grenadier Pond on Saturday in a phenomenon conservation officials call a die-off.

"Small die-offs are not uncommon, but this seems to be bigger than usual," according to the Ministry of Natural Resources.

Die-offs can occur in hot or stormy weather, from temperature shifts in the water or a change in oxygen levels, a spokesperson says.

But there is no immediate explanation for the deaths of the blue gill sunfish in Grenadier Pond this week.

Three city staff will begin removing the dead fish from the water early Saturday morning using skimmers.

David Chapman, parks supervisor for the York Etobicoke District, said the workers won’t be venturing into the water and will return in the coming days to see if more fish have surfaced.

Fish sent for testing

The fish are visible all along the edge of the water, and there is a strong smell coming from the pond.   Four fish have been sent to the University of Guelph to uncover the cause of the mass death. 

Water samples were also taken to check for contaminants in the water. Test results will come back in several weeks.

Until then, it’s up to the city to clean up the dead fish. The ministry says both humans and pets are asked to avoid eating any dead or dying fish.