Fish Die Off in Boundary Creek by Winnipeg Beach

Wednesday morning I was in Gimli and heard about a fish die off which had occurred on Monday at Boundary Creek which enters Lake Winnipeg at Winnipeg Beach. There is a marina at the mouth of the creek, and when we stopped there during the morning, there were still a lot of dead fish (photos above).

Apparently on Monday there was almost a "carpet" of small fish on Boundary Creek. Most of these were quickly scooped up by gulls. But the many dead fish still present show the fish kill was extensive.

The reason for the die off is unknown, but needs to be investigated. Could the rains on the weekend have washed some toxins into the creek and caused the die off? If so what were the toxins and where did they come from? If not, what caused the die off?