Stream Regulation Alters Acute Temperature Preferenda of Red Shiners, Notropis lutrensis

Abstract

Acute selected temperatures at acclimation states of 10, 20, and 30 °C were significantly different (P < 0.05) between red shiners (Notropis lutrensis) from an unregulated stream and a stream below a hypolimnion-release reservoir in north central Texas. Estimated final temperature preferenda for the two populations were 30.0 and 23.3 °C, respectively. These results support the hypothesis that temperature selection behavior in this species is mutable and subject to regulation by natural selection. We hypothesize that the lower thermal preferendum of tailwater populations represents an adaptive response to a depressed thermal regime typical of hypolimnion-release reservoirs.Key words: temperature preferendum, regulated stream, red shiner, Notropis lutrensis