Application of microparticle diets for Japanese flounder Paralichthys olivaceus larvae

Abstract

A feeding trial was conducted with two newly developed microparticle diets (MD-Q and MD-V), which differed in the mixing ratios of two types of casein hydrolysates (C700 and C800) as the protein source. The ratio of C700 and C800 were adjusted to 7:3 in MD-Q and 6:4 in MD-V, respectively. Japanese flounder larvae were fed from 7 days after hatching (d. a. h.) to 32 d. a. h. on live food (LF), MD solely, MD+1/3 LF (either of the MD and one-third quantity of the live food) and 1/3 LF (one-third quantity of live food alone), respectively. They were then switched to Kyowa diet B from 33 d. a. h. until 40 d. a. h. The larvae fed on MD-Q exclusively had a higher survival rate (36.4%) than those fed on MD-V (24.2%) by 22 d. a. h. Unfed larvae could survive up to only 12 d. a. h. Larvae fed on MD-Q+1/3 LF also had a significantly higher survival rate (34.2%) than those on MD-V+1/3 LF (16.3%) and 1/3 LF solely (15.4%) at 32 d. a. h. These results suggest the potential of MD-Q as a part replacement for LF from the early developmental stage in the seed production of Japanese flounder.