Ectoparasite Prevalences of Grouper Fish (Epinephelus fuscogutatus x Epinephelus polyphekadion) Cultured in Floating Net Cages

Monitoring the health of the reared fish in a floating net cage (FNC) is often conducted by examining their ectoparasites. This study determines ectoparasite prevalences of grouper fish (Epinephelus fuscogutatus x E. polyphekadion). The study site was conducted in the Pongok Island, South Bangka Regency. The health examination of fish and ectoparasites was carried out by applying simple random sampling during three periods (November 2016 (I), February 2017 (II) and May 2017 (III)). Hydro-oceanography survey was done every month throughout three years. The grouper checkings (I, II and III) indicated the prevalences of ectoparasites in these periods were 43.3%, 8.8% and 13.5%, respectively. The mortality rate of fish was highly in the period I among other periods while the survival rate at harvesting time was only 70% from initial seed stocking (1,500 fish in total). The intensities ectoparasite throughout the were 1.6, 1.6, and 1.5, respectively. The result implied that every 10 groupers would potentially be attacked by at least 15-16 ectoparasites. A slow seawater current flow triggered the quick uplifting of the ectoparasites from the seafloor. The water condition at the FNC location in 2011 and 2017 was still under the quality standard. The ectoparasites were originated from the surrounding environment of the FNC location. The fish culture management should inevitably focus on cleansing the ectoparasites attaching on the groupers, dusting the net cage clean, and arranging the harvest pattern on a particular month following the surrounding environmental condition to prevent ectoparasite attacks.