Identification of factors affecting the growth and survival of the settling Japanese flounder larvae, Paralichthys olivaceus

• Published in: Aquaculture 2003-03, Vol.218 (1), p.309-327
• Main Authors: Dou, Shuozeng, Masuda, Reiji, Tanaka, Masaru, Tsukamoto, Katsumi
• Format: Article
• Language: English
• Subjects: Animal aquaculture; Animal behavior; Animal productions; Aquaculture; Artemia; Biological and medical sciences; Fish; Fish production; Fundamental and applied biological sciences. Psychology; Growth and survival; Light regime; Marine; Paralichthys olivaceus; Pisciculture; Prey density; Settling flounder larvae Paralichthys olivaceus; Shelter; Stocking density; Vertebrate aquaculture
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/S0044-8486(02)00531-8

A series of experiments were conducted to identify the factors that affected the growth and survival of the settling flounder larvae Paralichthys olivaceus. Settling larvae 24 days after hatching (DAH) were reared in 10-l experimental tanks up to 40 DAH, and two of the following factors were changed as controlled factors in each experiment: light regime (24L:0D or 12L:12D), prey density (1500, 3000, or 5000 Artemia l −1), shelter (sand or no sand) and stocking density (5, 10, or 15 fish l −1). Early settling larvae (24–35 DAH) experienced little mortality (less than 10% of the overall mortality) that was not significantly affected by above factors. In contrast, late settling larvae (36–40 DAH) suffered high cannibalistic mortality, which was significantly influenced by each of the above factors. Larvae experienced significantly lower mortality at 10 fish l −1 level than at other densities. Larvae at 15 fish l −1 level had higher mortality than at 5 fish l −1 when all other factors were identical. Larvae at 3000 and 5000 Artemia l −1 treatments survived significantly better than at 1500 Artemia l −1, but no significant differences in larval mortality were found between the two higher densities. Larvae suffered higher mortality at low prey density or at the absence of sand when they were exposed to longer photoperiod. Low stocking density significantly improved the growth of the settling larvae. The average daily instantaneous growth rate ( G) at 5 and 15 fish l −1 treatments were 0.050 and 0.034, with the coefficient of variation (CV) in final length at 16.4 and 23.5, respectively. Daily instantaneous growth rate increased significantly from 0.033 in the 1500 Artemia l −1 to 0.041 and 0.045 in the 3000 and 5000 Artemia l −1, respectively, but no significant difference in larval growth existed between the two higher prey densities. These findings suggested that the optimal prey density for growth and survival of the settling flounder larvae at a stocking density of 5–15 fish l −1 was around 3000 Artemia l −1. Larvae that were exposed to 24L showed 20% increase in growth ( G=0.046, CV=18.7) than those exposed to 12L ( G=0.037, CV=20.5). Longer exposure to light significantly improved larval growth, provided sufficient food was available. Sand substrate did not show significant effects on larval growth, possibly because the larvae spent most of the time swimming or feeding in the water column during this stage.