Large rivers and associated floodplains were historically dynamic, diverse ecosystems, but most have been modified. We initiated a study of fish communities in wetlands of the Arkansas River to understand patterns of diversity and environmental gradients.  During summer 2005, we sampled fishes with a seine (3.1-mm mesh), mini-fyke nets (3.1-mm mesh), and experimental monofilament gill nets (3.8-8.9-cm mesh) at 31 sites along a 174-km reach of the Arkansas River.  Sites ranged in size from 0.5 – 390 ha and varied in degree of connectivity to the main channel (contiguous, intermittent, and isolated).  We collected 62 taxa, and richness ranged from 5-32 species across sites.  Nonmetric multidimensional scaling ordination identified structuring of the fish community along a gradient from intermittently connected and isolated floodplain wetlands characterized by high vegetative cover, low dissolved oxygen, and low pH (e.g., Centrarchus macropterus, Elassoma zonatum, and Amia calva) to contiguous backwaters having low vegetative cover and relatively high dissolved oxygen and pH (e.g., Dorosoma petenense, Menidia beryllina, and Opsopoeodus emiliae).  These data underscore the value of submerged vegetation to wetland fishes and suggest a mosaic of wetlands supporting a diversity of fishes continue to occur along the Arkansas River despite extensive modification to the system.