匙吻鲟仔稚鱼摄食特性研究

Feeding Habit of Larval and Juvenile Paddlefish(Polyodon spathula)

通过测定不同规格（全长15.2-95.5 mm）、不同水温（21.2℃、16.8℃）和一天当中匙吻鲟（Poly-odon spathula）仔稚鱼饱满指数的变化,研究了匙吻鲟仔稚鱼摄食特性。结果表明,在平均全长达到20.1 mm之前（约开口摄食3 d）,随着个体的生长,饱满指数逐渐增大并在20.1 mm达到最大值,且在规格相近的个体之间,饱满指数相差较大,最高达78.4倍。平均全长达到20.1 mm以后,随着个体的生长,饱满指数呈现下降的趋势,且在规格相近的个体之间,饱满指数相差较小。水温从21.2℃降到16.8℃,20.0-23.2 mm的仔鱼饱满指数降低53.3%。仔鱼具有明显的昼夜摄食节律,属晨昏摄食,全天出现1个摄食高峰和1个摄食低谷,从低谷到高峰,饱满指数呈强弱交替波动性上升。以＂时平均饱满指数法＂计算匙吻鲟仔鱼（16.3-21.0 mm）的日摄食率为6.5%。

Experiments were performed in indoor aquarium. Enough zooplanktons filtered with 120 mesh net were fed daily. The fullness index was measured for larvae of total length from 15. 2 to 95. 5 mm and under two different water temperatures （21.2℃, 16.8℃）. And the variation of fullness index was also measured for the same larvae within a day. Results demonstrated that feeding intensity increased gradually before juvenile growing to 20. 1 mm and reached the most when growing to 20. 1 mm. Even though the body sizes were nearly the same,the feeding intensity differed greatly, high up to 78. 4 times. After growing to 20. 1 mm,its feeding intensity decreased with the growth of juvenile; the difference of feeding intensity between individuals reduced. Besides differences among fries, it may mainly be related to the capability of gradual ingestion and the process of physiological adaptation to the appropriate ingestion. When water temperature decreased from 21.2 ℃ to 16. 8 ℃feeding intensity of juveniles with 20.0-23.2 mm body size decreased by 53. 3%. Juveniles had feeding rhythm feeding in the morning and night. There was a feeding peak in a day, with which feeding intensity changed accordingly. The feeding rate was 6. 5 % based on the mean fullness index. The experiment conditions including the illumination, the bait, the water quality and the dissolved oxygen were all optimized firstly. And the variation of water temperature was very small （about 1 celsius degree from 20 celsius degree to 21 celsius degree） in the experiment. But all these factors can not dominantly affect the ingestion of the larva paddlefish （Polyodon spathula）. It needs further studying next.