Fish abundance and diversity in Mid-Cross River, Nigeria, were studied monthly for 18 months commencing from March 2005 in order to stimulate sustainable management of the fisheries of the entire Cross River. Fish samples were collected from fishermen at four landing points and abundance and diversity determined. A total of 3,142 fishes belonging to 69 species, 39 genera and 21 families were assessed in this study. Nine species of Mochokidae, eight species of Mormyridae and Cichlidae, seven species of Clariidae, three marine intrusive species; Decapterus rhonchus, Trachinotus tersia and Caranx hippos; and the freshwater prawn Macrobranchium vollenhovenii, and other Macrobranchium sp were identified. The Cichlidae (50.19%) was the dominant family and the predominant species was Oreochromis niloticus (13.14%). ANOVA showed significantly higher fish catch in the dry season compared to rainy season (p< 0.001). Five fish species previously reported for this region were not encountered while others showed remarkable population decline and 42% of the families were monospecific. The result of this study raised the need for urgent and effective management of the fisheries of the Cross River to halt population depletion and species extirpation. It is advocated that such strategy should include the indigenous people and the conservation of some lakes within the region.