Prevalence of Ectoparasites in Cultured Catfish (Clarias gariepinus) in Ogun State Fish Farms

This study examined the prevalence and identity of ectoparasites infesting Clarias gariepinus cultured in earthen and concrete ponds in Ogun State, South West Nigeria. Ectoparasite infestations are a leading cause of morbidity and economic loss in Nigerian catfish aquaculture, yet systematic prevalence data from Ogun State remain limited. A total of 180 fish were randomly sampled from nine farms across three local government areas. Fish were examined using standard parasitological dissection techniques, with skin scraping, fin clipping, and gill examination performed under compound microscopy. Five ectoparasite taxa were identified: Gyrodactylus spp., Dactylogyrus spp., Trichodina spp., Argulus spp., and Lernaea spp. Overall prevalence was 58 percent, with Trichodina spp. and Gyrodactylus spp. recorded as the most prevalent genera. Farms with high stocking densities and irregular water exchange showed parasite burdens up to 3.7 times higher than well-managed farms. Seasonal analysis revealed higher prevalence during the dry season, coinciding with reduced water volume and increased fish stress. No significant difference in prevalence was observed between earthen and concrete pond systems when management intensity was controlled. Clinical signs associated with heavy infestation included excessive mucus production, fin erosion, anaemia, and mortality in juvenile fish. The study recommends routine fish health monitoring, prophylactic salt bath treatments, and optimised stocking management to reduce ectoparasite burdens in Ogun State aquaculture facilities. Keywords: ectoparasites, Clarias gariepinus, aquaculture health, fish disease, Ogun State