Spatial Rhythm and Periodic Pattern of Fish Species in Eniong River, South Eastern Nigeria

The spatial rhythm and periodic pattern of fish species was studied  in lower and upper streams in Eniong River, Southeastern Nigeria for 12 consecutive months (April, 2019- March, 2020) using standard  methods and procedures. A total of 178 individuals of fish species belonging to 14 families and 25 species were recorded in the study. The results revealed species abundance in favour of the lower stream with only two species: Clarias macromystax (Clariidae) and Malapterurus electricus (Malapteruridae) not found in the lower stream. Populations were generally bigger in lower stream 122 (69.32%) than their counterparts in upper stream with 56 (30.68%) samples. The family Cichilidae dominates the lower stream while Clariidae dominates the upper stream. The result of Jaccard Index Similarity of the number of species found between the upper stream and lower stream revealed the value of 0.461˂50%. The overall range of fish sampled falls within (9.7-25.5cmTL) with size structure generally bigger in the wet season than in the dry season.  Species had seasonal abundance in the wet season than the dry season.  In the wet season, Oreochromis niloticus and Clarias macromystax were the most abundant species in June and September (wet season) while Malapterurus electricus and Citharinus citharus were not found in the wet season. In the dry season, twelve (12) species were completely absent-Hepsetus akawo, Ctenopoma nebulosum, pollimyrus asperses, Marcusens senegaleusis, Ccoptodon zelli, Cclarias gariepinus, Cclarias macromystax, Synodontis obesus, Schilbe mystus, Schilbe uranoscopus and Protopterus annectens and Hemichromis fasciatus. The most abundant species found in both dry and wet seasons were Oreochromis niloticus, Chrysichthys nigrodigitatus and Hemichromis fasciatus. The fish diversity ranges from typical freshwater fishes to brackish species. The greatest dissimilarity between the wet and dry seasons’ samples was generated by Oreochromis niloticus. The study recorded the highest species richness (Margaleaf) and diversity (Shanno-Wiener) in the wet season with 23 species while the lowest with the smallest abundance was observed in the dry season with 13 species. The study recommends low exploitation in the upper stream and in the dry season to enhance species productivity and sustainability in Eniong River, Southeastern Nigeria.