Development of aquaculture methods for southern flounder, Paralichthys lethostigma: II. Nursery and grow-out.

摘要

Nursery and growout trials of hatchery-raised southern flounder, Paralichthys lethostigma, were conducted in tanks and raceways using recirculating systems. Three-month-old juveniles were stocked at 0.5/litre in 800-litre round tanks and raised in sea water for three months before being acclimated to freshwater and transferred to a 24-ton raceway, where they remained until they were 14 months old. Fish were exposed to salinities ranging from 0-32 ppt and temperature ranging from 17-30°C. Southern flounder grew to an average 169 g (±68.92 SD) and 25.06 cm (±4.30 SD) in 420 days (14 months after hatching). Growth rates of 3- to 14-month-old southern flounder in this experimental trial are expressed by the exponential equation y=0.0773 e0.0188x (r2=0.77). Overall feed conversion ratio was 0.79. Survival rate of 22.5% was achieved during the nursery and grow-out trials. Mortality occurred mainly due to the outbreak of diseases such as ectoparasitic infestations of the copepod Argulus sp. and the dinoflagellate Amyloodinium ocellatus. A large number of slow-growing, stunted fish suggests that early selection of the fast-growing fish belonging to the large size class for grow-out is currently the best alternative for the successful culture of this species.