The Relation Between Reproductive Capacity of a Lake Trout Population and the Apparent Availability of Spawning Habitat in Megisan Lake, Ontario

Abstract

To compare the number of lake trout eggs deposited at spawning areas to the reproductive potential of a lake trout, Salvelinus namaycush, population, I estimated the area potentially available for spawning, the area used for spawning, the egg deposition rate, and the egg production potential of the lake trout population in Megisan Lake, Ontario. Megisan Lake, a 616 ha glaciated lake with a self-sustaining population of lake trout contained about 3,300 m2 of habitat apparently suitable for spawning. Lake trout deposited eggs in only about 840 m2 of this habitat. Egg densities estimated with buried egg-collection trays and an air-lift sampler were not significantly different (P < 0.05). Mean egg deposition estimated in 1989 from collections made at several spawning sites was 299 (sd = 42) eggs *m−2. There was no significant relationship between the density of lake trout eggs and water depth over the range, 0.2 to 1.2 m, in which eggs were found. The estimated total egg deposition (approximately 250,000 eggs) from our spawning survey was less than the mean egg production potential (718,300) of the estimated number of female lake trout but within the range for the female population. I was unable to use measures of substrate size, water depth or depth of interstices to differentiate potential and used spawning habitat.