News Environmental stress confirmed in Island lakes fish die-off issue SHARE ON: Rosalind Russell, staff Friday, Aug. 9th, 2019 Dead fish have been washing up on the shores of Lake Manitou on Manitoulin Island. The Ministry of Natural Resources and Forests is investigating. Photo supplied by RM Hutchinson. Weather and temperature changes led to a fish die-offs on two Manitoulin Island lakes in mid-July. The Ministry of Natural Resources and Forestry spokesperson Jolanta Kowalski confirmed the fish die-offs in Lakes Manitou and Mindemoya were the result of environmental stress. Kowalski says based on the available evidence, the mortality was related to environmental stress associated with the rapid warming of surface waters, following a late ice-out and cool spring. She adds the final results from testing at the University of Guelph found the dead fish showed no evidence of an infectious disease.