| Summary: | We studied movements by fishes in Chamberlain Creek, Montana, from 24 July to 16August 2001. We operated six weirs with two-way traps and one additional upstream trap,separated by 14–1,596 m, to quantify the timing, direction, and distance of movements and toestimate fish populations in the study reaches. We trapped and marked 567 fish of sevenspecies, including 368 westslope cutthroat trout (Oncorhynchus clarkii lewisi) and 172 sculpin(slimy sculpin (Cottus cognatus) and an unidentified species similar to mottled sculpin (C.bairdii)). We recaptured 173 westslope cutthroat trout and detected net movements as long as1,581 m (median, 91 m). Bidirectional movements for 116 westslope cutthroat trout ranged fromless than 18 to more than 1,581 m (median, 64 m). Sculpin moved as far as 209 m (median, 26m). We estimate that 14% of sculpin and 48% of westslope cutthroat trout were mobile during thestudy. We captured all species more frequently at night or twilight (n = 296) than during the day(n = 83) and more frequently moving downstream (n = 419) than upstream (n = 277). Theseresults demonstrate considerable summer movement by the fish community in a small stream
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