Fish assemblages in the riverside pools of a small stream

Abstract

Fish assemblages in the riverside pools of a small stream were investigated in Nagano Prefecture, Japan, and a total of 12 fish species were caught. There were greater numbers of Misgurnus anguillicaudatus and Cobitis biwae and fewer Tribolodon hakonensis and Zacco platypus in the riverside pools relative to the assemblage in the main stream. In the pools, fish species richness and total population density of fish were not correlated with the abundance of benthic invertebrates, but were strongly correlated with environmental factors. Fish species richness was highest when the degree of saturated dissolved oxygen was elevated in June and when the area and water depth were greatest in September. The total population density was positively correlated with the mean current velocity in June but was not correlated with any environmental factor in September. Fish fed primarily on chironomid larvae, ephemeropteran nymphs, benthic algae and detritus in the riverside pools. Detritus contributed to a greater proportion of the diet in the fish from the riverside pools compared with those in the main stream. © 2011, The Japanese Society of Limnology. All rights reserved.