Broodstock management and egg collection from reared wild-broodstock of Japanese flounder Paralichthys olivaceus fed commercial extruded pellets

Wild Japanese flounder Paralichthys olivaceus, captured by set-net fishery and reared on raw fish for about 2 years, were divided into two groups. One was fed frozen raw fish (RF group) and the other was fed commercial formula feed (FF group) in each tank for 8 months and 20 months in 2002 and 2003, respectively, before egg collection at the Miyazu Station of the National Center for Stock Enhancement. Broodstock in each group were induced by manipulations of both water temperature and photoperiod conditions to accelerate the maturation, and eggs were collected from each broodstock by induced spawning. Parameters of the FF group such as total number of eggs, fertilization rate, hatching rate, and survival rate of the larvae were compared with those of the RF group. The spawning results from the FF group in both years was slightly inferior to those from the RF group, but the activity, growth and survival rate of the larvae were almost the same. These results indicated that FF was efficacious for broodstock management of Japanese flounder and their egg collection.