Effect of Fishmeal Content in the Diet on the Growth and Sexual Maturation of Olive Flounder () at a Typical Fish Farm.

Olive flounder () is a commercially important and valuable species for aquaculture in Korea. Due to the unstable supply of fishmeal for farmed fish, an optimum fish-feed formulation should be researched to ensure the sustainability of aquaculture. This study investigated the effect of three experimental diets: Con (basal diet); FM (20% fishmeal replacement of CON); and FM (30% fishmeal replacement of CON) on over 20 weeks at a typical farm by monitoring the growth and factors relating to sexual maturation. The results showed that no differences in growth were observed between the CON and diet-replacement groups. Gonadal oocyte development was similar between the CON and diet-replacement groups. Moreover, sbGnRH and GH expression did not differ between the CON and diet-replacement groups. The levels of Erβ and Vtg expression were significantly higher in the FM group than in the CON and FM groups after the experimental period. The expression of PSS-I was significantly higher in the FM group than in the CON and FM groups. Therefore, although growth occurred when 30% of the fishmeal was replaced, such high dietary protein replacement may be ill-advised during the maturation of olive flounder at the commercial fish farm.