细鳞斜颌鲴仔鱼饥饿试验与不可逆点的确定

Experiments on starvation of Plagiognathops microlepis larvae and its PNR determination

【目的】研究细鳞斜颌鲴仔鱼不可逆点,确定其从孵化池移养至培育池塘的最佳时间,为人工育苗生产提供技术指导。【方法】对卵黄囊期细鳞斜颌鲴仔鱼分别进行饥饿与正常投饵的对比试验,观察内源性营养转化为外源性营养的过程中,饥饿对卵黄囊期仔鱼摄食、存活及生长的影响,确定其不可逆点。【结果】在27～29℃的水温条件下,初孵仔鱼卵黄囊体积为0.34934mm3,5日龄消失;3～4日龄为内源性营养与外源性营养的混合期,最高初次摄食率(96.7%)出现在5日龄,至6日龄下降到46.7%,即进入不可逆期,具有初次摄食能力的时间约7d。与正常投饵的仔鱼(仔鱼存活率约75%,瞬时生长率0.2383)相比,饥饿组仔鱼从4日龄开始,其存活率明显下降,至15日龄全部死亡;在生长方面,也是4日龄以前保持较快的生长速度,但此后逐渐出现负增长,其瞬时生长率仅0.1093。【结论】在27～29℃的水温条件下,人工繁育的细鳞斜颌鲴仔鱼宜在3日龄时从孵化池移养至培育池,同时提供适宜开口饵料。

[Objective]In order to provide technology for artificial breeding in Plagiognathops microlepis larvae, the best time from hatching pond to culture pond was studied by determining PNR. [Method ]The comparative experiment on starvation and normal feeding of larvae was carried out to investigate the effects of starvation on feeding, survival and growth of Plagiognathops mierolepis larvae during yolk sac period, and PNR was identified when endogenous nutrition was shifted to exogenous nutrition. [ Result ]At water temperature 27-29℃, a newly hatched Plagiognathops microlepis larvae had the yolk-sac size of 0.34934 mm^3. The yolk was absorbed at the age of 5 days. The mixed feeding stage of en- dogenous feeding and exogenous feeding occurred at the age of 3-4 days. The period of initial feeding took about 7 days. The highest feeding rate appeared on 5-day age, and one day later the feeding rate fell down to 46.7% at 6-day age, marking the entrance of PNR period. Compared to feeding larvae （ survival rate ： 75 % ; instantaneous growth rate ： 0.2383 ） , survival rate of starved larvae dropped dramatically from 4-day age, and they all died on 15-day age. Further they grew relatively faster before 4-day age, but then showed negatively growing and the instantaneous growth rate was only 0. 1093. [ Conclusion ] At water temperature 27-29℃, the optimal time of Plagiognathops microlepis larvae shifting from hatching pond to artificially breeding pond was recommended as 3-day age with providing suitable feeding.