Summer feeding and distributional behavior of threespine stickleback, Gasterosteus Aculeatus, in Lower Jean Lake, Alaska, 1974

Abstract

In 1974, the University of Alaska, Institute of Marine Science, in cooperation with the Alaska Department of Fish and Game, initiated a study of the ecology of the threespine stickleback Gasterosteus aculeatus, in a sockeye salmon nursery lake. This thesis reports some aspects of summer feeding and distributional behavior observed in Lower Jean Lake, Alaska. Sticklebacks utilizing the pelagic region of the lake and nearshore environment fed extensively on zooplankton; copepods, rotifers, and drowned winged insects predominated. Sticklebacks sampled on the lake bottom exhibited a preference for benthic invertebrates including harpacticoid copepods, ostracods, and gastropods. These diets overlapped with foods preferred by the juvenile salmon. However, the young sockeyes relied more heavily on winged insects. Stickleback distribution patterns during the summer are complex and apparently related to the age of the fish and their state of maturity. These distributions are also modified by behavior related to time of day.