饥饿对点带石斑鱼饵料转换期仔鱼生长和发育的影响

在盐度29、水温27.8~28.8℃的条件下,进行点带石斑鱼仔鱼饥饿实验,确定仔鱼初次摄食饥饿不可逆点(PNR);观察饥饿条件下点带石斑鱼饵料转换期(初孵仔鱼,5、8、10、15和20日龄)的存活与生长、油球利用、鳍棘生长和游泳行为的变化。结果表明:点带石斑鱼从初次摄食到PNR期仅2~3d,这个耐受饥饿的时间临界点发生在孵化后的第5天,即转入外源性营养的第3天。在饥饿条件下初孵仔鱼,5、8、10、15和20日龄仔鱼的全部死亡时间分别为7 d、3 d、4 d、3 d、4 d和6 d;半数死亡时间分别为5 d、1.5 d、2 d、1.5 d、2d和3.5d,说明5日龄和10日龄是点带石斑鱼早期发育中最为敏感的阶段。饥饿会延缓初孵仔鱼对油球的利用。随着饥饿时间的延长,仔鱼的生长与正常条件下仔鱼的生长差异显著(P<0.05)。饥饿仔鱼体长较短,头大且体瘦,长期饥饿后脑后部下陷;行为变化表现为表层集群游动觅食,游动缓慢,反应迟钝和静伏底。

Effect of starvation on the growth and development of the larvae of Epinephelus malabaricus Bloch & Schneider in the process of food transformation

Under the water temperature of 27.8～28.8℃ and salinity of 29,the starvation trial and the definition of the point of no return(PNR) for the larvae of Epinephelus malabaricus were conducted.The effects of starvation on survival,growth,use of oil globules,growth of the second spine of dorsal fin and the first spine of ventral fin,and swimming behavior of Epinephelus malabaricus larvae at an age of 0,5,8,10,15 and 20 days were studied.The results showed that the PNR of larvae appeared on the 5 days after hatching.The survival rate of larvae varied with the developmental stages,0 d,5 d,8 d,10 d,15 d and 20 d after hatching,larvae were dead under 7,3,4,3,4 and 6 days of starvation respectively,and the half-death time of the larvae were 5 d,1.5 d,2 d,1.5 d,2 d and 3.5d respectively,which indicated that the 5 d and 10 d after hatching larvae were the most sensitive stages to starvation in the process of food transformation in the early life stage. Starvation delayed the use of oil globules,and the length of larvae was significantly smaller than that of normal larvae in control group(P<0.05).The body became shorter and thinner,but bigger in head.Posterior part of brain became sunken after long time of starvation.The behavioral responses of Epinephelus malabaricus larvae to starvation might be divided into three stages: congregate in surface water and search food;be slow in swimming and reacting;be rest in bottom.