Feeding habits and possible interactions between alien rainbow trout and native salmonids in a small stream on Shiretoko Peninsula, northern Japan

Abstract

Ichthyofauna and feeding habits of salmonid fishes were investigated in a small stream on Shiretoko Peninsula, northern Japan. Dolly Varden (Salvelinus malma), white-spotted charr (S. leucomaenis), masu salmon (Oncorhynchus mason) and rainbow trout (O. mykiss) inhabited the stream. Rainbow trout, an alien species in Japan, dominated the lower reach of this stream, which is concrete-lined. Dolly Varden, a native species, dominated the upper reach, which has a mainly natural riverbed. White-spotted chary and Dolly Varden mainly consumed terrestrial and aquatic invertebrates, respectively. The smaller rainbow trout foraged for aquatic invertebrates, while larger ones consumed various animals including of gobies (benthic fish).