Status of Oreochromis niloticus (Linnaeus, 1758) Fishery in Liberty Reservoir, Jos, Nigeria

Abstract

Oreochromis niloticus samples (n = 203) were bought from one of the fishermen who fish in the reservoir on 31 October 2016. The fish were caught in fish traps. Length (mm) and weight (g) measurements of each fish were determined in the laboratory. The least-squares regression method (95% Confidence Level) was used to determine the length-weight relationship of the fish. The condition of the fish was also assessed by calculating the condition factor K. The size of the fish ranged from 62 to 292 mm total length and 50 to 244 mm standard length. The weight ranged from 4.2 to 324.2 g. Although there was a significant relationship between total length and weight (P<0.0001; r2 = 0·945; slope = 2.855) the majority of the sampled fish were small. Approximately 64% of the fish were < 125 mm total length, and about 90% of them weighed < 90 g. The condition factor (K) of the fish ranged from 0.35 to 4.21, with majority (96%) of them having a K value of 2.01 to 4.21 and, hence, were in good condition. Fish that were judged to be in poor condition had a K value that ranged from 0.35 to 1.98. In view of the fact many small fish were retained by the fisherman, and, indeed, by the other fishermen, the fishing mortality was judged to be quite high. The Plateau State Government of Nigeria needs to acknowledge the current clandestine fishing and develop appropriate regulations. Monitoring and enforcement would help to ensure sustainability of the valuable O. niloticus fishery. Suggestions regarding appropriate and realistic fisheries management options are proffered.