Seasonal Distribution of Eurytemora affinis (Poppe, 1880) (Copepoda; Calanoida) in Freshwater Lake Ohnuma, Hokkaido

Abstract

The seasonal distribution of Euryterrwra ajJinis in the inland freshwater Lake Ohnuma, in southern Hokkaido, was investigated from June 7, 1984 to August 29, 1985.In Lake Ohnuma, E. affinis occurred for ten months from mid-April to the following February in a year, that is, all months other than the ice covered period.The nauplii appeared in mid-April, when adults were not observed.Adult females carrying eggs occurred in early May, and then the population density increased during the warm season, being 8.0 x 10' inds.m-3 at maximum in early June of 1984 and 1985.No recruitment was found between February and mid-April.