Mysis Relicta: Production, Vertical Migration and Life History of the Lake Ontario Population, 1984

Abstract

Mysis relicta was sampled in Lake Ontario biweekly with vertical tows from May through November, 1984. Two sites were studied off Sandy Creek, one station at 35m and the other at 100m. At the 35m station, total abundance values ranged from near zero in late September to 207/m2 in mid-August, with a mean abundance of 48 organisms/m2. Average biomass and production values at the 35m station were 0.08 dry g/m2 and 0.13 dry g/m2/7 months, respectively. At the 100m station, total abundance ranged from 110/m2 in late September to 860/m2 in mid-July, with a mean abundance of 378/m2. 0.68 dry g/m2 was the average biomass and 1.23 dry g/m2/7 months was the total production at the 100m station. Mysis relicta abundance increased from 1971 to 1984 in the offshore and nearshore of Lake Ontario. This may be related to the stocking of salmonines in Lake Ontario or the significant die-off of adult alewives in the winter of 1983-1984. Samples were also taken to study the vertical migration habits of the Mysis relicta population at two sampling sites near Nine Mile Point in Lake Ontario. Amplitude of migration was greater at the 75m station (mean = 27.2m) than at the 35m station (mean = 9.8m).