Susceptibility of spotted halibut Verasper variegatus (Pleuronectidae) to infection by the monogenean Neobenedenia girellae (Capsalidae) and oral therapy trials using praziquantel

Abstract This study investigated the susceptibility of spotted halibut Verasper variegatus (Pleuronectidae) to infection by the capsalid monogenean Neobenedenia girellae and sought an effective treatment method against this monogenean species in advance of its culture to enable a stable production of V. variegatus by farming. Our results showed that V. variegatus is susceptible to N. girellae . In oral therapy trials, the anthelmintic praziquantel in feed was found to be antiparasitic against infestation by N. girellae on V. variegatus , and a low-dose treatment for a long period, such as 40 mg/kg body weight (BW)/day for 11 days, was more effective compared with treatment of a high dose for a short period (i.e., 150 mg/kg BW/day for 3 days). The number of N. girellae on V. variegatus was significantly lower than for Japanese flounder Paralichthys olivaceus (Paralichthyidae) when both species were exposed to oncomiracidia in the same aquarium. Considering the lower susceptibility of V. variegatus for this parasite species and the effectiveness of using praziquantel, V. variegatus may be a promising species for stable production by aquaculture.