Abstract
Forested floodplains are a mosaic of periodically flooded aquatic habitats with variable levels of connectivity. While there is a clear link between riparian forests and freshwater organisms, floodplain forests are seldom investigated due to difficulties in sampling structurally complex and periodically inundated habitat. This lack of research has led to large knowledge gaps that hinder our understanding of the conservation value of these unique, complex systems for inland fisheries. Therefore, we aimed to determine how bottomland hardwood forests influence fish taxonomic and functional diversity. To accomplish this goal, we: (1) assessed species taxonomic diversity (i.e., species richness and composition) and functional diversity (i.e., standard length and body shape), and (2) quantified habitat complexity. Both objectives were completed along spatial and temporal scales in the Pascagoula River of Southern MS. We hypothesized that fish taxonomic and functional diversity are driven by forest complexity. Overall, A total of 51 fish species (1,487 individuals) were captured. Ordination analyses per hydrological period revealed consistently different assemblages in floodplain forest sites compared to river channel sites, yet, periodic connectivity facilitated longitudinal movement of fishes across the floodplain. Floodplain forests also contained a higher taxonomic diversity than the river channel. Additionally, no fish species were shared among all sites. Regression models showed that fish standard length was negatively affected by increased water surface temperature in the river channel. However, water surface temperature had no effect on fish standard length in the floodplain forest. Interestingly, the water surface temperature in floodplain forest sites was cooler than in river channel sites, even in the warmer parts of the year, which indicates that floodplain forests act as a thermal refugia for fish. These results emphasize the importance of floodplain forests to the conservation of inland fisheries in the face of current threats such as climate change, deforestation, and dams.
