Summer Microhabitat Use and Diet of Four Sympatric Stream-dwelling Salmonids in a Kamchatkan Stream
Resource utilization by four sympatric, stream-dwelling salmonids, masu salmon Oncorhynchus masou, coho salmon O. kisutch, steelhead trout O. mykiss, and Dolly Varden Salvelinus malma, wasstudied by underwater observations of microhabitat use and foraging behaviour, and dietary analyses, in a third order tributary of the Bolyschaya River on the Kamchatka Peninsula, Russia in summer, 1993. The Oncorhynchus species differed considerably in microhabitat use, with little overlap. Juvenile masu salmon and coho salmon utilized, respectively, areas of swift and moderate current speed, without selectivity for water depth and overhead cover, whereas steelhead trout selectively occupied deeper water with overhead cover, regardless of current velocity. Dolly Varden were more evenly spread across the stream channel, being closely associated with the stream bottom, whereas the other species selected the mid layer portion of the water column. The latter were typical drift foragers, whereas Dolly Varden adopted both drift and benthos foraging. Stomach content composition differed markedly between masu salmon, steelhead trout, and Dolly Varden. The diet of coho salmon, however, overlapped those of masu salmon and Dolly Varden, but not that of steelhead trout. These results indicated that the four Kamchatkan salmonids were segregated along several niche dimensions in summer, which is considered to be one of the important mechanisms allowing coexistence of these species in lotichabitats.
- Fisheries science : FS
Fisheries science : FS 61(6), 926-930, 1995-12-01