Mp. Zimmerman et Rm. Parker, RELATIVE DENSITY AND DISTRIBUTION OF SMALLMOUTH BASS, CHANNEL CATFISH, AND WALLEYE IN THE LOWER COLUMBIA AND SNAKE RIVERS, Northwest science, 69(1), 1995, pp. 19-28
We used two indices derived from catch and effort to compare density a
nd relative abundance of smallmouth bass Micropterus dolomieu, channel
catfish Ictalurus punctatus, and walleye Stizostedion vitreum vitreum
among reaches (forebays, mid-reservoirs, tailraces) and reservoirs of
the lower Columbia and Snake Rivers, and among unimpounded sampling z
ones in the Columbia River downstream from Bonneville Dam, Smallmouth
bass density was highest in forebay and mid-reservoir reaches of Snake
River reservoirs. Density was greatest in lower Snake River reservoir
s, intermediate in Columbia River reservoirs, and lowest in the Columb
ia River downstream from Bonneville Dam. Smallmouth bass were most abu
ndant in Lower Granite Reservoir. Channel catfish were distributed thr
oughout all reaches within reservoirs. Density was far greater in the
Snake River than in the Columbia River. Walleye density was low throug
hout the lower Columbia River, and walleye were absent in the Snake Ri
ver upstream from Ice Harbor Dam. Distribution and relative abundance
of introduced piscivorous fishes indicate that predator-prey relations
hips differ among reservoirs, between impounded and unimpounded reache
s, and between the lower Snake and Columbia rivers. Differences in the
relative abundance of introduced predators should contribute to varia
tion in losses of juvenile salmonids to resident predators.