Several Virile Crayfish gathered together close to shore in shallow water. The warm weather during late March had increased the water temperature to 10C. This appeared to trigger some breeding activity as seen in the second photo. By April 4th the water temperature had dropped to 5C due to a snow storm and active crayfish were no longer observed.
(Photographed April 3, 2016 in lower Chemong Lake, Emily Township, City of Kawartha Lakes, Ontario, Canada)