<![CDATA[Grouper is an important fish species due to high price both in domestic and international market. Several hybrid groupers have been released and can be accepted by farmers. A major production constraint in grouper culture is mortality due to disease. Leech is an ectoparasite for grouper which may cause significant loss, so that controlling this parasite is important as one of aquaculture management tools. The objectives of this study was to know the life cycle of leech on hybrid grouper and determine the efficacy of chemicals to kill leech under laboratory condition with diffferent dossage and immersing time. Life cycle was observed by reared an adult leech, counted the fecundity and observed the development of eggs until reach adult stages. The efficacy of formalin, albendazole, oxfendazole, levamisole, H2O2, CuSO4, ivermectin, vermizyn and freshwater on several concentration were assessed to kill adult leeches. All chemicals tested (except for freshwater), are dissolved in saline water salinity of 35 ppt at concentrations of 1000, 500, 250, 125 and 62.5 ppm. During 3 days of rearing, the adult leech could deposit of 11 eggs in average, with 600 µm – 800 µm in diameter. Twelve days were needed for the new egg inside the cocoon to hatch and develop into larvae under 24-25 °C at 34 ppt of salinity. It took another 9 days for the leeches larvae to grow reach mature stage. Five chemicals were able to kill leeches (Zeylanicobdela arugamensis), which were fresh water, formalin, levamisol, ivermectin, and CuSO4. Treatment by exposure leech to freshwater for 30 minutes shows effective to kill leech. Treatment with formalin with a dose of 250 ppm was able to kill leech after 1 hour immersion. ]]>
