| Summary: | This study shows recent infestations of ectoparasites on farmed tilapia (Oreochromis sp.) from the Sarawak region, Malaysia, and their relationships with the water quality in the area. The prevalence and mean intensity were investigated for a total of 120 tilapia obtained from four distinct farms in 2022 and 2023. The entire tilapia specimens were infected with at least one ectoparasite species, showing a 100% prevalence rate of ectoparasite infestation. Six species of protozoans (Trichodina sp., Ichthyopthirius multifiliis, Ichthyobodo sp., Oodonium sp., Epistylis sp., and Ciliates sp.) and two species of monogeneans (Dactylogyrus sp. and Gyrodactylus sp.) were observed. The most intense ectoparasites recorded were Ciliates sp., Trichodina sp., and Dactylogyrus sp. Trichodina sp. and Dactylogyrus sp. were recorded higher in tilapia collected from Kuching district, while Ciliates sp. infected the tilapia from Miri district the most. The lowest intensity rates were recorded for Ichthyobodo sp. and Oodinium sp., where Ichthyobodo sp. was only observed on tilapia from Mukah district while Oodinium sp. was only recorded in fish from Miri district. The highest rates of infestation prevalence and intensities of ectoparasites were shown in the station containing highest concentrations of phosphate (PO43-), total ammonia nitrogen (NH3-N), and nitrite (NO2-). The results also demonstrated high ectoparasites infestation on the samples obtained from the pond with high temperature, dissolved oxygen, and pH readings. These conclude the positive relationship of the prevalence and intensity of ectoparasites infestations with the water quality of the water body. The information provided might be useful to the fish farmers in understanding the dynamics of tilapia parasites in the relevant area. © Published under licence by IOP Publishing Ltd.
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