Cage culture of Nile tilapia (O. niloticus) in Lake Volta accounts for about 80% of the total annual aquaculture production in Ghana. In the past decade, however, cage farms in Lake Volta have experienced numerous disease outbreaks resulting in high mortalities and economic losses. Unfortunately, most efforts on fish disease in Ghana have focused on bacterial and viral infections, while far less attention has been given to parasitic infestations. However, fish parasites, especially ectoparasites, have the potential to cause mortalities by increasing the risk of secondary bacterial and viral infections. This study, therefore, sought to identify the ectoparasites present in Nile tilapia cage farms in Ghana, estimate their prevalence, mean intensity, and density.
A structured questionnaire with both closed and open-ended questions were administered to 30 Nile tilapia cage farms to obtain information on the peak period of occurrence of ectoparasites in these farms. Fish were sampled from selected farms for ectoparasites identification over a period of 6 months (Feb. – July 2023). The selected farms were located at the up-, mid- and down streams of Stratum II of the Volta Lake – the hub of aquaculture in Ghana. A total of 900 fish were randomly collected from five farms and transported live to the laboratory for examination. Ectoparasitic identification was done using a combination of taxonomic keys and identification guides. The ectoparasites were counted and their prevalence, intensity and abundance of infestation estimated. Ectoparasites belonging to the genera Trichodina, Ichthyophthirius, Dactylogyrus, Gyrodactylus, Cichlidogyrus, Diplostomum, Myxosporean and Argulus were encountered. Two were species unidentified. Trichodina, Dactylogyrus, Gyrodactylus and Cichlidogyrus were present in all farms except Myxosporean, Argulus, Diplostomum, Ichthyophthirius and the two unidentified species which occurred in some of the farms. Trichodina sp. were the most prevalent parasites in all farms, while Ichthyophthirius was least prevalent.