Occurrence of a monogenean gill parasite Pseudorhabdosynochus epinepheli on red spotted grouper Epinephelus akaara and its experimental treatment by hydrogen peroxide bathing

Since 1997, infection of a monogenean gill parasite Pseudorhabdosynochus epinepheli has been occurring in red spotted grouper Epinephelus akaara at the Kagawa Prefectural Sea-Farming Center, Japan. The efficacy of hydrogen peroxide (H2O2) bathing was examined in vivo. Bathing in a 700 ppm H2O2 solution for 45 min at 10 or 15 deg C, or for 15 min at 20 or 25 deg C, with infected fish of 230-2100 g in body weight, resulted in 100% mortality of P. epinepheli on the gills. Mortality occurred in fish (550-1730 g) bathed for 30 min or longer at 25 deg C, but not in fish bathed for at least 60 min at 10, 15 or 20 deg C. Results indicate that chemotherapy with H2O2 has a high potential as an effective treatment for P. epinepheli infection in red spotted grouper.