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Tank-reared Japanese flounder larvae, Paralichthys olivaceus, had a major feeding peak in the morning and a secondary peak in the afternoon throughout the larval development, with light being the primary factor regulating their feeding activity. The larvae consumed rotifers in preference to Artemia for up to 10 days, after which the food preference shifted to Artemia. Feeding rates of the larvae prior to 10 days post-batch depended on prey density, but in the old larvae, feeding rates were independent of prey density. Maximum feeding rate occurred at 19 degrees C. The occurrence of the attack posture, after its onset at first feeding (2 days post-hatch), increased up to 25 days, began to decrease when the larvae prepared to settle down, then disappeared after settlement. The occurrence frequency of the attack posture was positively related to fish density, but inversely related to starvation duration, and occurred most frequently at 19 degrees C. This posture depended on prey density in larvae prior to 10 days post-hatch, but became independent of prey density as the larvae developed. It was obvious that, for flounder larvae, attack posture was a behavioural character closely related to feeding and subject to larval development and environmental factors. (C) 2000 The Fisheries Society of the British Isles.

市販飼料およびタンパク質源にアミ粉末, 脱塩アミ粉末および沿岸魚粉で作製した試験飼料(アミ粉末含量82.0%, 脱塩処理アミ粉末含量77.5%, 37.5%, 0%)を用いて, 0.16gおよび1.35gのヒラメ稚魚を14日間飼育しアミの栄養価を検討した。その結果, 脱塩処理アミ粉末含量77.5%飼料区の飼育成績は未処理アミ粉末82.0%区に比較し著しく改善され, 飼料中の過剰な塩類(主にNaCl)は稚魚の成長を低下させることが明らかになった。なお, 1.35gの稚魚は, アミ粉末添加により市販飼料より優れた飼育成績を示したことから, アミに多量に含まれる遊離アミノ酸(FAA)の有効性が示唆された。