Feeding periodicity, diet composition, and food consumption of subyearling rainbow trout in winter

Although winter is a critically important period for stream salmonids, aspects of the ecology of several species are poorly understood. Consequently, we examined the diel feeding ecology of subyearling rainbow trout (Oncorhynchus mykiss) during winter in a central New York stream. Rainbow trout diet was significantly different during each 4-h interval and also differed from the drift and benthos. Feeding was significantly greater during darkness (i.e. 20:00 h – 04:00 h) than during daylight hours (i.e. 08:00 h – 16:00 h), peaking at 20:00 h. Daily food consumption (1.9 mg) and daily ration (3.4 %) during winter were substantially lower than previously reported for subyearling rainbow trout in the same stream during summer. These findings provide important new insights into the winter feeding ecology of juvenile rainbow trout in streams.