ASPECTS OF BIOLOGY OF BARBUS OCCIDENTALIS (CYPRINIDAE) FROM RIVER UKE, NASARAWA STATE, NIGERIA

Studies on aspects of biology of Barbus occidentalis (Cyprinidae) in River Uke, Nasarawa State, Nigeria was conducted during wet and dry seasons. La Motta Tracer (model 1766) was used to determine the physicochemical parameters. 219 specimen were obtained from fisher folks on landing site using fishing gears such as cast nets, traps from march-august. The specimen were used to determine morphometric parameters (length, weight, depth, eye diameter), age using the scales, fecundity with gonad and stomach content analysis using numerical and frequency of occurrence methods. The study showed that the mean values of the physicochemical parameters obtained were D.O 2.5-5.1mg/L, Temperature 27.0-32.1oC, pH 6.8-8.0, salinity 20-70ppm, TDS 70-110ppm, EC 20-161μS. The weight of Barbus occidentalis sampled ranged from 15.0-996.9g. The highest male weighed 996.9g while the highest female weighed 620g. The length and weight relationship of Barbus occidentalis were (r=0.858) and regression exponent (b<3) in both sex. Only four age groups 0+, 1+, 2+,3+ where noted during the study period. The stomach content analysis result shows that the fish fed mostly on phytoplankton (Cyanophyceae, Chlorophyceae, Filamentous algae), three groups of zooplankton encountered were copepods, cladocerans and nematode, and they also fed substantially on anthropods, fish remains, insect larval and benthos organisms. The gut weight showed no significant difference between wet and dry season 0.645 (p>0.01). Fecundity ranges from 1257-6576, the relationship between fecundity and other parameters were highly significant (0.928) indicating positive correlation between biological parameters and fecundity. The physicochemical parameters obtained were higher than those of the wet season, the length and weight relationship of Barbus occidentalis showed positive correlation and regression exponent showed negative allometric growth pattern. The mean condition factor K showed that the condition and the wellbeing of a Barbus occidentalis is good, there is a correlation between some physicochemical parameter of River Uke and biological parameters of the specimen. The four age groups noted during the study period means the fish is over-exploited. Stomach content analysis result shows that the fish is omnivores. The physicochemical parameters obtained were within acceptable range for aquatic life. The result of this study has revealed that the fish were in good condition with high reproductive potentials. Hence adequate regulation is required as to enhance sustainability of this important fish in River Uke