Effect of Two Novel Experimental Microdiet Types on Growth, Survival, and Pigmentation during the Weaning Period of the Fine Flounder, Paralichthys adspersus, Larvae

The aim of this study was to evaluate two new types of experimental weaning microdiets for fish larvae, using the same formulation, but with different manufacturing processes, microextrusion marumerization (MEM) and particle-assisted rotational agglomeration (PARA). Both microdiets were compared to a commercial microdiet, Otohime (OTO), during the weaning of the fine flounder, Paralichthys adspersus. Weaning was achieved by cofeeding with live food from 40 to 50 d after hatch (d.a.h.). Thereafter, only the microdiets were fed to the end of the study (60 d.a.h.), where the total length, dry weight, and survival rates were 15.9 +/- 3.20, 14.3 +/- 1.72, and 14.4 +/- 2.28mm; 8.83 +/- 3.40, 5.53 +/- 2.85, and 7.10 +/- 3.56mg; 18.1, 16.3, and 15.2%, for OTO, MEM, and PARA, respectively. The dry weight and total length were significantly higher (P<0.05) for larvae fed OTO compared with those fed MEM. There were no differences between the other comparisons. Based on these results, any of the two experimental microdiets can be used for future investigations. However, we recommend the PARA microdiets because the manufacturing process produces less-dense and smaller particle size diets, reducing sinking rates and increasing the probability of the larvae in detecting and ingesting the diet.