Establishment and application of prevention and control methods against parasites of fish cultured in the Philippines

Abstract

The efficacy of bath treatment methods against the ectoparasites Amyloodinium ocellatum, Pseudorhabdosynochus lantauensis and Zeylanicobdella arugamensis on marine fish was determined under laboratory conditions. The toxicity of formalin and hydrogen peroxide (H₂O₂) to orange-spotted grouper (Epinephelus coioides) were also investigated. Freshwater or 200 ppm H₂O₂ bath treatments for 1 hr were effective against the dinoflagellate A. ocellatum on hatchery-reared mangrove red snapper (Lutjanus argentimaculatus). Hydrogen peroxide at 200 ppm for 1 hr was effective in eliminating the gill monogenan P. lantauensis on E. coioides fingerlings. In vitro treatments of the marine leech Z. arugamensis using 250 ppm formalin for 3 hr significantly killed the parasite. Chlorine at 50 ppm for 1 hr can be used to disinfect leech-contaminated facilities. The computed 3 hr and 6 hr LC₁₀ (10% lethal concentration) of formalin to E. coioides fingerlings is 322 ppm and 275 ppm, respectively, at 28°C. The 9 hr LC₁₀ and LC₅₀ (median lethal concentration) of H₂O₂ to grouper are 255 and 298 ppm at 28°C.