Parasitosis of pond-reared Nile tilapia (Oreochromis niloticus L.) in Central Luzon, Philippines
2011
Reyes, A.T.
This study has provided an inventory of parasites in pond-reared Nile tilapia [Oreochromis niloticus (L.)] in Central Luzon, Philippines during dry season and has evaluated the influence of biological and physico-chemical factors, and farm management on the intensity and prevalence of the parasites. Six genera of ectoparasites (Trichodina, Coleps, Euplotes, Dactylogyrus, Gyrodactylus, Ergasilus) and three taxa of endoparasites (Camallamus, Acanthocephala, Digenean) were recorded. Results showed that Trichodina posted the highest prevalence and intensity followed by Dactylogyrus and Gyrodactylus. Host body size and spleen size were negatively correlated with ectoparasite intensity but positively correlated with endoparasite intensity. Juvenile tilapia had higher ectoparasite intensity than adult. Female tilapia was found more vulnerable to ectoparasites than male. Moreover, farms practicing semi-intensive management recorded the lowest ectoparasite prevalence and intensity. Based from the results, slight differences in physico-chemical conditions between collection sites were due to the differences in stocking densities (3-11 fish/sq m). Temperature had an overall positive effect on ectoparasite occurrence. The effectiveness of chemotherapeutics against Trichodina-infected Nile tilapia fingerlings was also assessed. Results showed that salt as treatment was found more effective against the parasite. In conclusion, environmental factors could influence the level of parasitosis in pond-reared tilapia but show very little consistency in the results. The study emphasized that biological factors and farm management can be a better predictor of parasite prevalence and intensity.
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