Monogenean parasites, Fish farms, Clarias gariepinus, Prevalence, Intensity, Abundance, Calabar

Abstract

Objective: To determine the prevalence, mean intensity, and abundance of monogenean parasites in Clarias gariepinus (C. gariepinus) from two selected fish farms in Calabar, Cross River State, Nigeria. Methods: Eighty specimens of C. gariepinus from the two farms (40 each) were necropsied for parasitological analysis. Skin, gill and fin biopsies were prepared from each specimen following standard methods for microscopic analysis. Parasitological indices including dominance (D), prevalence, mean intensity and abundance were calculated according to standard formulae. Data were analyzed using the Fisher's exact test. Results: C. gariepinus from the two farms were infested with a total of ninety individuals of monogenean parasites belonging to three species including Macrogyrodactylus clarii (M. clarii), Gyrodactylus sp. and Dactylogyrus sp. D index showed that the three monogenean species were eudominant (D-value > 10%). Gyrodactylus sp. was more abundant (46) followed by Dactylogyrus sp. (23) while M. clarii was the lowest (21). Prevalence, meaning intensity and abundance of monogenean parasites in the two farms, varied insignificantly higher (P > 0.05). Prevalence in both farms were higher in female C. gariepinus than that in male. Monogenean parasites exhibited organ specificity as M. clarii and Dactylogyrus sp. were recovered from the gills while Gyrodactylus sp. colonized the skin and fin. Conclusions: High abundance of these parasites may lead to poor growth performance and high mortality in C. gariepinus, leading to huge monetary loss and low profit margin by increasing production cost due to the cost of treatments.