Freshwater Fish Diversity of a Tropical Rainforest River in Southeast Nigeria

Fish samples were collected at three stations twice per month from January to December 2013 with the help of local fishers using hook and line, gill net, cast net, bagnet and local traps for ecological studies of important fish species and resource management issues of Oramiri-Ukwa River, southeast Nigeria. An estimate of 25 fish species, 15 genera, 21 families and six orders were obtained. Ecological indices indicate a polydiverse community and no single species exhibited true dominance (? 50%). Paired group cluster analysis establishes Tilapia zilli and Hemichromis fasciatus as the focal species and identifies the associated species combinations that characterize spatial variability and account for the biodiversity resources and structure of the artisanal fishery. Other important species include Tilapia mariae>Synodontis nigrita while Polypterus senegalus>Parachanna africana and Shilbe mystus were the least in number. Monospecific and rare fish species of ecological and conservation significance identified include Ctenopoma kingsleyae, Clarias gariepinus as well as Erpetoichthys calabaricus and Pantodon buchholzi derived from interconnections with other African rivers. This study presents lower fish diversity compared to earlier reports. This difference may be linked to increased human activities and fluctuating biotic and abiotic factors of the ecosystem, among others. Keywords: Abundance, biodiversity, conservation, rare specie