マダイ稚魚の成長および体成分に及ぼす選別の影響

概要

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In order to examine the effects of size-selection on growth and body constituents of red sea bream juvenile, two experiments were carried out using Lot 1 (76 days, 36.1±4.6mm) and Lot 2 (65 days, 29.9±5.4mm). In experiment I, the small size group (S-1; 31.8±2.0mm, n=70) were selected from Lot 1. As a control, a medium size group (M-2; 31.7±1.9mm, n=70) were selected from Lot 2. Rearing was conducted for 48 days, mixing the S-1 group with the M-2 group. In experiment II, the large size group (L-2; 37.4±1.6mm, n=70) and medium size group (M-1; 38.1±1.8mm, n=70), selected from Lot 2 and Lot 1, respectively, were also compared. No differences of size distribution and daily growth rate after 48 days rearing were observed between the S-1 and M-2 groups. The growth and size distribution of the L-2 and M-1 groups also showed no marked difference. The size-selection enhanced not only the RNA/DNA ratio but also lipid and triglyceride accumulation in the small size group. These results indicate the usefulness of the size-selection and suggest that runty fish can grow as well as medium size fish.