Morphometric Indices and Parasitic Incidence of Synodontis nigrita from Lower River Benue, Makurdi, Nigeria

The study was carried out to determine the morphometric indices and parasitic incidence of 160 fresh samples of Synodontis nigrita comprising of 80 samples each of female and male sexes.  Fish samples were obtained from the catches of local fishermen along Lower River Benue at Wadata fish landing site of Benue State. Length–weight relationship was analyzed using the equation W=aLb. The condition factor of the fish samples was determined using the equation, K=100W/L3. Samples of Synodontis nigrita were later subjected to parasitological examination using standard parasitological method. The mean total length, body weight, condition factor, regression and correlation coefficients were higher for un-infested female samples of Synodontis nigrita than the infested female. Similarly, the mean total length body weight, condition factor, regression and correlation coefficients of un-infested male samples of Synodontis nigrita were higher than the infested males. A total of three hundred and fifty seven (357) parasites were recovered from 76(47.50%) infested samples. Out of the 357 parasites, 251 were recovered from 49(61.3%) infested female samples, 106 parasites were recovered from 27(33.8%) infested male samples. Among the infested parts of the female samples, the intestine accounted for the highest number/percentage (116/46.4%) parasite load, the least 2(0.8%) was recorded for the skin. Between the external parts (gill and skin) of the female fish samples, while the gill recorded the higher number of parasite load 28(12.8%), skin recorded 2(0.8%). Similarly, among the infested parts of the male samples, the intestine accounted for the highest number/percentage (65/61.3%) parasite load, the least 9(8.5%) was recorded for the gill. Between the external parts (gill and skin), the gill recorded 9(8.5%) number/percentage parasite load, no parasite was recovered from the skin. Prevalence (61.25), number of parasites (251) and intensity (5.10) of parasite infection were higher for female samples compared to the male with the prevalence, and intensity of parasite infection of 33.80, 106 and 3.90, respectively. However, the chi square value showed that there was no significant difference (p>0.05) in the prevalence, number of parasites and intensity of parasite infection between the sexes of Synodontis nigrita. Variation in the prevalence and intensity of parasite infection of female and male Synodontis nigrita based on size groups existed. However, it was generally observed that longer and heavier sized fish of both sexes were more infested with higher number of parasites than the smaller sized samples of both sexes.