Environmental Influences on Extended Spawning of Rainbow Trout (Salmo gairdneri)

Abstract
Variations in discharge and water temperature influenced movements of spawning rainbow trout between Lake Huron and Bothwellˈs Creek. Adults entered the stream between 29 October and 15 May, with numerical peaks in late December, and between 16 February and early April, following major freshets and associated rising water temperatures. Between 31 January and 13 February, during a period of minimal stream discharge and low water temperatures to 0.3 C, no new fish entered the stream, but spent and spawning‐scarred fish moved downstream, and disappeared after a mid‐February freshet. Spent trout of the later run moved downstream during late April and early May. Spawning occurred first on 27 December in the upper reaches at 6 C, and by early January elsewhere in the stream. Activity increased with rising water temperatures, peaking during late March and early April at water temperatures of 6 to 8 C. Aborted attempts at spawning occurred on 2 June. Viable eggs resulted from December and January spawning at water temperatures of 0.3 and 2.0 C.

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