Diurnal shift in trout microhabitat in the Maple River, Emmet County.

Abstract

The objective was to evaluate the trout (Salmo trutta, Salvelinus fontinalis, and Oncorhycus mykiss) in the Maple River, Emmet County to determine if there is a diel shift in microhabitat. Trout were located by snorkeling upstream, and then they were observed to determine length and height from the stream bed. During the morning and evening times the trout were farther from the stream bed and swimming at a higher velocity which corresponded to a greater metabolic rate. Six drift nets were placed in the stream and pulled four times during the day. The higher number of invertebrates caught in the drift nets correlated with the high metabolic rate of the trout. To determine if the free drift corresponded to what the trout were eating several trout were taken for stomach contents analysis. The stomach contents contained similar species as the free drift, and the percentage were relatively similar. The data suggests that the higher metabolic rate in the morning and evening correspond to a greater net gain in ration.