Diplostomum species are the parasites responsible for diplostomiasis in fish which may cause blindness, eyefluke, severe ocular disease, opacity of the lens and many other affections. The parasites use many organisms including fish as a host. African catfish is one of the widely distributed fish species in tropical Africa and has become one of the most important culturable fish species in Africa especially in Nigeria. This study examined the occurrence of Diplostomum species in farm raised African catfish in Oyo state. A total of two hundred and sixteen eye samples were collected from 108 fishes in 36 farms. The eye lens and vitreous body were examined for the presence of Diplostomum species. The data obtained were analysed using descriptive statistics and regression analysis to the relationship between the eye size and parasite occurrence. The result shows that 33.18% of the samples had Diplostomum species. Males had higher occurrence (23.53%) than the females (9.65%). There were statistically significant differences in the percentage, intensity and index of infection between males and females (p = 0.010, p = 0.003, and p = 0.012 respectively) while the density of infection between both sexes was not statistically significant (p = 0.063). The relationship between eye diameter and occurrence of the parasites shows positive relationship Pearson correlation (R2 = 0.125). In conclusion, Diplostomum species are present in farm raised African catfish in Oyo state-Nigeria with a positive relationship between the eye diameter and occurrence of the parasites.

Several studies have shown the positive effect of phytase on phosphorus utilization by fish and animals, with the use of phytase sources determined for different fish species. Few studies have tested phytase response to different diets, which may affect nutrient availability for optimum growth due to differences in phytate location. The research, therefore, studied the effect of phytase to diets based on soya bean and groundnut meal for Clarias gariepinus on nutrient availability and growth. In trial 1, four groups of soya bean S1, S2, S3 and S4 replaced fish meal at 25%, 50%, 75% and 100% and supplemented with 250, 500, 750 and 1000 FTU/g phytase, respectively. In trial 2, four groups of groundnut meal diet G1, G2, G3, G4, G5 and G6, were similarly supplemented with the same phytase levels used in experiment 1. Fish meal control (S0=G0) was not supplemented with phytase. Result showed that 250 FTU/g phytase showed the highest mean weight gain for both plants. In conclusion, the research has shown that the chemical nature of phytate, rather than its Uzezi et al.; ARRB, 31(4): 1-21, 2019; Article no.ARRB.26092 2 concentration and location, may influence the utilization of phosphorus for optimum growth in the fish by supplementing 250 FTU/g, with a range of available phosphorus requirement of between 0.75% (Y = 0.363 + 4.155X -2.772X 2 , R 2 = 0.759) and 0.80% (Y = 0.307 + 3.303X -2.059X 2 , R 2 = 0.210) Original Research Article

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