Critical Stream Velocities for Young-of-Year Smallmouth Bass in Relation to Habitat Use

Abstract
We defined relationships between current velocity and displacement of young smallmouth bass Micropterus dolomieui from nests, and between velocity and the distribution, swimming, respiration, feeding, and growth of larger young. Young that had recently risen from the nest gravel (7–9 mm standard length, SL) were displaced from field nest sites and from laboratory flumes at low velocities (8 mm/s). Nests in areas of higher velocities (15 mm/s) failed to produce young. Comparison of respiration and foraging rates of young fish (16–71 mm SL) in laboratory flumes suggested that the ratio of feeding reward to energy expenditure reached a maximum at current velocities between 80 and 130 mm/s. This velocity range produced maximum growth in the flumes and was also the range most frequented by young (43–116 mm SL) in the Mississippi River.

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