Spotted sunfish habitat selection at three Florida rivers and implications for minimum flows

摘要

Abundance of the spotted sunfish Lepomis punctatus has been positively correlated with interannual fluctuations in river stage, making this a potential indicator species for streamflow management. We evaluated patterns of habitat selection by adult and juvenile spotted sunfish and related them to simulated declines in river stage at three southwestern Florida rivers (Anclote, Little Manatee, and Manatee rivers). To identify habitat selection patterns, we used multivariate analysis of variance to compare measured characteristics (i.e., current velocity, depth, and cover abundance) of habitats used by spotted sunfish with those of randomly located habitats within the stream margin environment. Spotted sunfish generally selected habitats with greater structural complexity than the average available habitat. In many instances, spotted sunfish appeared to select habitats that contained both large and fine woody debris. However, fish were collected from a variety of habitat types (luring the study, indicating that this species is somewhat general in its habitat use. We found few significant differences in habitat measures between juvenile and adults, suggesting that habitat selection was similar between these life stages. Our model simulations indicated that 0.3-m reductions in average daily river stage could reduce habitat availability for spotted sunfish by 20-70% across systems. Spotted sunfish used habitats with greater-than-average resiliency to stage declines (i.e., deeper, more complex habitat). Considering that even minor reductions in the average daily stage during fall and spring could substantially reduce overall availability of suitable habitat, the inundation of complex habitat types is probably important for spotted sunfish.