Development of microparticle diets for Japanese flounder Paralichthys olivaceus larvae

Two newly designed microparticle diets (MD), with two kinds of peptide (C700 and C800) as a protein source were developed. Microparticle diet Q (MD-Q) contained C700 (molecular weight similar to30 000 Da) and C800 (molecular weight 1000-2000 Da); in contrast, microparticle diet T (MD-T) contained C700 only. Two separate trials, representing larvae from different hatches, were conducted. Japanese flounder Paralichthys olivaceus larvae were fed newly designed MD or a combination of them with live food (LF) between 3 and 10 days after hatching (d.a.h.) in experiment 1, or between 11 and 20 d.a.h. in experiment 11, and compared them to LF and a commercial diet (CD) feeding groups. The growth and survival rates in both experiments were the highest in the LF treatment. But in the microparticle treatment larvae fed MD-Q had a higher survival rate and better growth than those fed MD-T either alone or in combination with LF First-feeding larvae fed on MD-Q had a 20.5% survival rate and 1.12 mm gain by 10 d.a.h. Unfed larvae died within 6 d.a.h. These results indicate that using a mixture of different molecular weight peptides is good protein sources and also this type of microparticle diet can be applied to flounder from larval to juvenile stages.