Optimal Feeding Position for Stream Fishes in Relation to Invertebrate Drift

Abstract

The vertical and horizontal distributions of invertebrate drift, and the horizontal distribution of macrobenthic animals, were studied in a mountain stream to define advantageous feeding positions for visual feeding stream fishes during the summer season. The diurnal drift abundance of benthic or fallen animals were respectively linearly or exponentially correlated with the current speed. The estimated total daytime amounts of invertebrate drift passing downstream through the study pool reached about 72 g in wet weight, of which fallen drift accounted for 73 %. It is therefore suggested that the swift surface