<p>Of the original 21 million acres of bottomland hardwood forest from southern Illinois to coastal Louisiana, only 20 percent remains. We evaluated contrasting fish communities among floodplain ponds and the influence of biotic and abiotic determinants on fish assemblage structure across a 1.68 km² area of permanent and semi-permanent floodplain pond habitats in the Cache River watershed, Illinois. We surveyed seven floodplain ponds using mini fyke nets over the span of three years. Fish assemblage structure and life history frequencies differed among floodplain ponds. Floodplain ponds closer to each other had more similar assemblage structure than floodplain ponds farther apart. Historical connectivity, distance to other ponds, and local environmental variables (tolerance to low water level, pond permanence, water temperature, and dissolved oxygen) were correlated with fish assemblage structure and life history frquencies in the floodplain ponds. Differences in fish assemblages among floodplain ponds were associated with different life history strategies, pond connectivity, and hydrology, such that opportunistic species were associated with floodplain ponds that were unstable and more isolated from other floodplain ponds (low maximum water depth, variability in water depth, temperature, and&#xa0;dissolved oxygen), whereas equilibrium and periodic species were associated with ponds that were more stable and historically connected to other floodplain ponds. Maintaining a diversity of floodplain wetland types, habitat heterogeneity, and assessing water elevation thresholds that result in connectivity were identified as important factors for conserving fish biodiversity in remnant riverine swamps.</p>