延迟投饵对奥尼罗非鱼仔鱼摄食、生长和存活的影响

在盐度为5‰,水温(28±0.5)℃的条件下,对延迟投饵0~7d的奥尼罗非鱼(Oreochromis niloticus×O.aureus)仔鱼摄食、生长与存活进行了研究,并确定了仔鱼的饥饿不可逆点(PNR)。试验于仔鱼开口的当天开始试验。结果显示:仔鱼于3日龄开口;延迟投饵0~7 d组,投饵2 h后仔鱼摄食发生率分别为20%、100%、83.3%、36.7%、13.3%、6.7%、3.3%和0%,各组之间差异显著(P<0.05);延迟投饵在2 d以内,10日龄仔鱼体长和体重与对照组无显著差异(P>0.05),延迟投饵超过2 d,体长和体重显著低于对照组(P<0.05);奥尼罗非鱼仔鱼存活率随延迟投饵天数增加而降低,延迟0~2 d的10日龄仔鱼的存活率相差不大,介于78.6%~79.3%,各组差异不显著(P>0.05),延迟投饵超过2 d的仔鱼存活率较低,介于0%~33.3%;奥尼罗非鱼仔鱼的不可逆点出现在仔鱼开口后第4 d,开始投喂的最佳时间在仔鱼开口后的3 d之内。

Effects of Delayed Initial Feeding on Foraging, Growth and Survival of Hybrid Tilapia Larvae

Experiments were conducted to investigate the effects of delayed initial feeding on foraging,growth and survival of hybrid tilapia larvae.At the water temperature of(28±0.5)℃and salinity of 5‰,the delayed initial feeding trial and the determination of the point of no return(PNR:when 50% of the unfed larvae were unable to feed when offered food)for the larvae of hybrid tilapia were conducted.The influence of delayed initial feeding on survival and growth of larvae were observed.The results showed that the larvae opened their mouth at the age of 3 d,with delayed initial feeding of 0～7 d,the feeding incidence was 20%,100%,83.3%,36.7%,13.3%,6.7%,3.3% and 0% respectively,each group differed significantly(P<0.05);there was no significant difference in the body length and weight of the larvae with delayed initial feeding within 2 d,but dropped significantly if the feeding was delayed more than 2 d(P<0.05),when larvae was at the age of 10 d;the survival of the larvae decreased with the delayed initial feeding time,the survival was 78.6%～79.3% if the first feeding was delayed less than 2 d,but the larvae with delayed feeding of more than 2 d had significantly low survival rate,only 0%～33.3%;the larvae occurred PNR at 4 d after the mouth opened and the optimum initial feeding time for the larvae is within 3 d after mouth opened.