Identifying Life-History Traits That Promote Occurrence for Four Minnow (Leuciscidae) Species in Intermittent Gulf Coastal Plain Streams

Abstract

Life-history traits of stream fishes partly reflect adaptations to disturbance regimes, which in turn shape assemblage composition via environmental filters. In this study, we focused on life-history traits of 4 morphologically similar leuciscid species in coastal plain streams of southwestern GA that are shifting from historically perennial to intermittent flow. We evaluated the following traits hypothesized to influence species persistence in intermittent streams: differences in reproductive timing, sex ratio, body size at maturity, reproductive investment, and diet. First, we ordinated published species occurrence data for samples of fish communities in perennial and intermittent streams in the study region, and identified 4 focal taxa as differing in their associations with intermittency. We then periodically sampled individuals of the focal taxa in 14 streams over a year (May 2016–April 2017). We found that for Pteronotropis harperi (Redeye Chub), a species strongly associated with intermittent streams, reproductive timing did not overlap with typical seasonal stream drying. Redeye Chub also had the significantly smallest minimum length at maturation and the greatest reproductive investment. Fishes associated with perennial streams (Pteronotropis grandipinnis [Apalachee Shiner] and Notropis texanus [Weed Shiner]), or not associated with either stream type (Notropis petersoni [Coastal Shiner]), had at least a portion of their reproductive timing overlapping with times when streams were likely to dry, and had similar and significantly lower reproductive investment than Redeye Chub. Redeye Chub displayed no shift in diet when streams ceased flowing, while Apalachee Shiner showed decreases in terrestrial prey. Our results suggest that size at maturity, reproductive timing, and reproductive investment may promote persistence by the Redeye Chub given projections of more frequent and intense periods of stream intermittency.