ヒラメ仔魚の成長と変態に及ぼす飼育水温の影響〔英文〕

概要

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The growth, development and metamorphosis of larval flounder Paralichthys olivaceus were examined at three temperatures of 13, 16 and 19°C in the laboratory. Under conditions of sufficient food supplies and reasonable stocking densities, temperature markedly influenced the larval growth, development and metamorphosis. The larvae grew to 20mm TL in 79, 44 and 33 days after hatching, especially during postlarval stage with average growth rates of 0.22, 0.43 and 0.59 mm/day at 13, 16 and 19°C, respectively. The integrated water temperatures in which fish grew to 20mm TL were approximated as being 970, 700 and 620°C day at 13, 16 and 19°C, respectively. Larval development was also prominently influenced by temperature, the mean residence time at each developmental stage (ten stages from hatching to early juveniles) was estimated as being 3, 4-5 and 8-9 days at 19, 16 and 13°C, respectively. Fish sizes immediately after complete metamor-phosis were found to be dependent on the ambient water temperature: the average body length at the last stage of metamorphosis was 11.0, 12.4 and 13.5mm BL (after fixation) at 19, 16 and 13°C, respectively. It was speculated that, in higher temperatures, the development and metamorphosis of flounder larvae rather than growth were stimulated.