条石鲷仔鱼饥饿试验及不可逆点的确定

在盐度29、水温22~24℃的条件下,进行了条石鲷仔鱼饥饿试验和不可逆点(PNR)的确定;观察了饥饿条件下条石鲷初孵仔鱼、3、6、9、12、15日龄的存活、生长、卵黄囊与油球利用和游泳行为的变化。结果表明: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差异显著(P<0.05)。条石鲷仔鱼从初次摄食到PNR期为2.5~3 d,这个耐受饥饿的时间临界点在孵化后的5~5.5 d。在饥饿的条件下初孵仔鱼、3、6、9、12、15日龄仔鱼的全部死亡时间分别为6.5、6、5、4、65、d;后5个日龄仔鱼半数死亡时间分别为4、3.5、3.5、3.5、3.5 d。说明9日龄是条石鲷早期发育中最为敏感的阶段。饥饿仔鱼体长较短,头大且体瘦,长期饥饿后脑后部下陷。饥饿仔鱼表层集群游动觅食,缓慢游动反应迟钝,静伏底。

Starvation and Point of No Return in Striped Knifejaw Oplegnathus fasciatus Larvae

Striped knifejaw Oplegnathus fasciatus larvae were starved to determine the point of no return(PNR)at water temperature of 22～24 ℃ and salinity of 29. The survival, and changes in oil globules and yolk-sac volume, growth and swimming behavior in the larvae were observed 0, 3, 6, 9, 12 and 15 days after starvation. The results showed that starvation led to delaying of the use of oil globules, and to the significantly smaller body length than that in the normal larvae in control group(P<0.05). The PNR occurred 5～5.5 days after hatch and the subsistence larvae 0, 3, 6, 9, 12 and 15 d after hatch were death 6.5, 6,5, 4, 6 and 5 days after starvation, respectively.The LC_(50) time of the larvae were 4, 3.5, 3.5, 3.5 d and 3.5 days, respectively, indicating that 9 days was the most sensitive stage to starvation in the early life stage in the larvae. The larvae had shorter body length, bigger head, thinner body and posterior cupped part of brain after being starved for long period. The behavioral responses of the larvae to starvation was divided into three stages:congregating in the surface water, swimming slowly and searching for food; slowly swimming; morphological transformation and resting in the water bottom.