Susceptibility of Young-of-the-Year Fishes to Downstream Displacement by Flooding

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Abstract
I examined downstream displacement of young-of-the-year fishes (primarily centrarchids and cyprinids less than 25 mm total length, TL) by field sampling of drift during floods and by an experiment conducted in a 4.9-m-long artificial stream channel. The pattern of drift during a June 1985 flood (stage increase of 3.2 m) in Brier Creek, Oklahoma, indicated that both centrarchids and cyprinids smaller than 10 mm TL were extremely susceptible to downstream displacement. Drift rates of larger fish (10-25 mm) during both the June flood and a smaller flood (stage increase of 0.4 m) in July 1985 suggested that these fishes were much less susceptible to displacement. The rapid decline in susceptibility to displacement with increase in size from the field study coincided with results obtained in the artificial channel. These results suggest that the effects of floods on stream fish communities can depend on small differences in the timing of reproduction and of flooding.