Impact of water quality and morphometric indices on the spatio-temporal prevalence of fish endo-parasites and diversity in the Ase River, Niger-Delta, Nigeria.

Three stations along the Ase River, Delta State Nigeria provided water and 85 fish samples which were analyzed. The fish were measured and examined for endoparasites according to established protocol. All water quality parameters investigated were within the WHO-acceptable values for surface waters. Station variation of physicochemical parameters was not statistically significant (p > 0.05). Fish body conformation indices positively correlated with the prevalence of parasites in Clarias gariepinus, Heterobranchus longifilis, Parachana africana, Chromidotilapia guntheri guntherii, and Denticeps clupeodes. The overall parasite prevalence of 63.53% was established with the most abundant parasite being Trichodina mutabillis. The parasites had a predilection for the gastrointestinal tract with a high occurrence of 307 individuals. Stations 1, 2, and 3 had 326, 213, and 259 parasites, respectively, out of a total of 798 parasites detected. P. laevis was absent in station 1. All parasites were found in stations 2 and 3. Statistically, there was a significant difference (p < 0.05) in the prevalence in all stations. The correlation index of T. mutabillis and R. congolensis in stations 1 and 3 was positively strong (p < 0.05) with the concentrations of water quality. However, water conditions in stations 1 and 3 had a deleterious impact on P. laevis. T. mutabillis maintained a high positive correlation with physicochemical water quality in all three stations. Shannon-Weiner's index in station 3 (H = 1.337) shows that the parasites were more diverse. PCA and biodiversity indices have enabled us to comprehend how parasite-host-environment systems interact.