Author: Wilton, M.L. 1985. Water drawdown and its effects on lake trout (Salvelinus ncmayaush) reproduction in three south-central Ontario lakes. Ont. Fish. Tech. Rep. Ser. No. 20: iii & 9 p.

Observations and data gathered from Bark Lake indicate that reproduction of lake trout (Salvelinus namaycush) is no longer possible because of water drawdown of as much as 10 m annually. The fishery is now sustained by hatchery plantings. Data and observations from Mary Lake indicate that natural reproduction of lake trout may be severely curtailed at one of two shoals due to winter drawdown of as much as 0.83 m. Bella Lake has no dam or water level drawdown. Spawning occurs in less than 0.3 m but ice thickness lessens toward shore and as a result, there is no egg loss.

The area located between the Ottawa Valley and Georgian Bay, south of the French and Mattawa Rivers and north of the Kawartha Lakes, contains many oligotrophic lakes which provide suitable environments for lake trout (Salve-1-inus namayaush’) • Water control structures at the outlets of many of these lakes regulate water levels for hydroelectric generating stations downstream, as well as for cottage and recreational demands. Water drawdowns in these lakes characteristically occur during late fall and winter and coincide with the incubation period of lake trout eggs. The purpose of this paper is to document observations on lake trout spawning and water drawdown in three of these lakes.

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