Fish Recruitment is Influenced by River Flows and Floodplain Innundation at Palachicola River, Florida

High human demand for limited water resources often results in water allocation trade-offs between human needs and natural flow regimes. Therefore, knowledge of ecosystem function in response to varying streamflow conditions is necessary for informing water allocation decisions. Our objective was to evaluate relationships between river flow and fish recruitment and growth patterns at the Apalachicola River, Florida, a regulated river, during 2003-2010. To test relationships of fish recruitment and growth as responses to river discharge, we used linear regression of (i) empirical catch in fall, (ii) back-calculated catch, via cohort-specific catch curves, and (iii) mean total length in fall of age 0 largemouth bass Micropterus salmoides, redear sunfish Lepomis microlophus and spotted sucker Minytrema melanops against spring-summer discharge measures in Apalachicola River. Empirical catch rates in fall for all three species showed positive and significant relationships to river discharge that sustained floodplain inundation during spring-summer. Back-calculated catch at age 0 for the same species showed positive relationships to discharge measures, but possibly because of low sample sizes (n=4-6), these linear regressions were not statistically significant. Mean total length for age 0 largemouth bass in fall showed a positive and significant relationship to spring-summer discharge; however, size in fall for age 0 redear sunfish and spotted sucker showed no relation to spring-summer discharge. Our results showed clear linkages among river discharge, floodplain inundation and fish recruitment, and they have implications for water management and allocation in the Apalachicola River basin. Managed flow regimes that reduce the frequency and duration of floodplain inundation during spring-summer will likely reduce stream fish recruitment.