INFLUENCE OF WATER QUALITY ON PARASITE PREVALENCE IN NILE TILAPIA (Oreochromis niloticus Linnaeus, 1758) IN CULTURE SYSTEMS IN SIDAMA REGION, ETHIOPIA

Abstract

Parasitic infestation can lead to severe retarded growth and mortalities in high intensities in fish under culture systems. Importantly, the quality of water in the culture facility may influence the parasitic infestation. This study aimed to evaluate the influence of water quality on parasite prevalence in Nile tilapia, Oreochromis niloticus L,1758 in culture systems in Sidama Region. The study used a cross-sectional design from December 2023 to May 2024. Water physico-chemical parameters such as temperature, dissolved oxygen, pH and turbidity were measured in situ by following standard procedures. Water samples for nutrient contents such as ammonia, nitrate and nitrite were analyzed. A total of 240 O. niloticus (120 from Kokeb fish farm and 120 from CARE fish farm) were taken and examined in the laboratory for ecto and endo parasites by using stereo zoom dissection microscope. The parasitological aspects such as prevalence, mean intensity and mean abundance were calculated based on standard formulae. The results indicated that, the water quality parameters were significantly different (p<0.05) between both fish farms. The total number of parasite species recorded during the study was 11 species. While Kokeb fish farm showed 11 parasite species, there were only six species in CARE farm. Out of 240 fish sampled, 109 fish were infested representing an overall prevalence of 45.41%, mean intensity of 6.30 and mean abundance of 2.86. The prevalence, mean intensity and mean abundance in Kokeb farm were in the order of 59.16%, 7.46 and 4.41. In CARE farm, it was 31.66%, 4.48 and 1.30 respectively. The infestation showed a statistical difference (p<0.05) between the fish farms. There was a positive correlation between water quality and prevalence of parasite species, except dissolved oxygen. The size of O. niloticus and prevalence of parasite species was positively correlated (r=0.978). Prevalence of parasite species with sex of O. niloticus was statistically significant (x2=2.776, p<0.05). The Fulton’s condition factor of parasitized and non-parasitized O. niloticus showed no significant difference (p>0.05). Hematological effects of parasite species on O. niloticus between infested and non-infested groups were significant (p<0.05) except for neutrophil counts (p>0.05). The prevalence of parasite species was influenced by poor water quality. The study recommends that, to reduce or control parasite infestation in culture systems, there is an imperative need to undertake regular monitoring and management of water quality parameters in fishponds.