Temperature and Photoperiod Regulation of Rheotropic Behavior in Prespawning Common Shiners, Notropis cornutus

Abstract
The upstream orientation and frequency of upstream movement of prespawning common shiners, N. cornutus in response to a water current simulated by moving a striped background past the fish were observed at 3 temperatures (10, 15, 20.degree. C) and 2 photoperiods (12L:12D and 16L:8D). The greatest frequency of upstream movement was induced by a combination of spring day lengths and warm water temperatures. Further increases in the frequency of upstream movement followed immediate 5.degree. C increases in water temperature. Neither temperature nor photoperiod had a major effect on the frequency of upstream orientation. The significance of environmental regulation of rheotropism as a mechanism of upstream migration is discussed.

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