Effects of Mackerel Meal on Growth of Red Tilapia

Abstract

In order to investigate the feeding periodicity of the black porgy(Acanthopagrusschlegeli),three experiments were carried out.The stomach contentweight of the wild black porgy,the feeding amount and the feeding frequencyunder the natural photoperiod,and the growth rate under the different feedingschedules were analyzed to evaluate their feeding circadian periodicity.(1)From the wild black porgy captured every two hours per day,theratio of the stomach content weight to the body weight was lower during8:00 to 18:00.The ratio was higher during night time with a superior peakat 22:00 and inferior at 6:00～8:00.(2)Fed by fresh prawn flesh or artificial synthesis diet in the laboratory,the experimental fish had the highest feeding amount and feeding frequencyat dusk 17:00.(3)Fed at dark or light period once or twice,the fish showed the highestgrowth rate from the group of fish fed twice during night time.The above three experiments demonstrated that black porgy probably hadnocturnal activities,feeding mainly during night time with superior feedingpeak at dusk and inferior peak at dawn.爲探討黑鯛(Acanthopagrus schlegeli)攝食日夜周期性(feeding circadian periodicity)，本實驗利用日夜不同時段所釣獲野生黑鯛之胃容量變化，及實驗室飼育黑鯛之日夜不同時段之攝食量及攝食頻率，並利用不同光照之不同投餵次數對黑鯛成長之影響，以分析黑鯛之攝食周期性。實驗結果如下：(1)野生黑鯛在自然生態中，其胃容量／體重比値在8:00～18:00間均低於0.9％，而夜間均較日間爲高，22:00呈現高峰，胃容量比値達1.8％，黎明呈小攝食峰(inferior feeding peak)。(2)實驗室飼育之黑鯛無論投餵新鮮蝦餌或人工合成餌料均在17:00呈最高之攝食總量與最高之攝食頻率。(3)不同光照周期與投餵次數對成長之影響，結果顯示最大成長率爲在夜間餵飼兩次者，而最低者在夜間僅餵飼一次者。綜合上列三項實驗結果，推論黑鯛具有夜間活動之攝食周期性，卽黑鯛在夜間能持續攝食，並以黃昏黎明之昏暗光照環境爲主要攝食峰。