马拉瓜丽体鱼仔鱼饥饿试验及不可逆点的确定

在（28±1）℃条件下对马拉瓜丽体鱼（Cichlasoma managuense）仔鱼进行饥饿试验,确定仔鱼的不可逆点（PNR）,并研究延迟投饵对仔鱼成活和生长的影响。结果显示,仔鱼在4日龄时开口摄食,进入混合营养期,持续3 d;7日龄时卵黄囊消失,进入外源营养期。初次摄食率开始时仅为15%,6日龄时的初次摄食率最高达100%,9日龄以后初次摄食率急剧下降,PNR出现在仔鱼孵出后第9至第10日龄。延迟投饵1～3 d对仔鱼的成活率影响不大,延迟投饵4 d以上仔鱼成活率明显下降。完全饥饿条件下仔鱼全长在0～8日龄为正增长,之后开始转为负增长。延迟投饵1～3 d的12日龄仔鱼全长无显著差异（P〉0.05）;延迟投饵超过4 d的仔鱼全长则有极显著差异（P〈0.01）。马拉瓜丽体鱼仔鱼的最佳投喂时间应在仔鱼开口后的3 d之内。

Experimental starvation on Cichlasoma managuense larvae and determination of point of no return

Under water temperature of （28 ±1 ）℃ a starvation trial was conducted on Cichlasoma managuense larvae to determine the point of no return （PNR） and to study the effects of delayed initial feeding on the survival and growth of the fish. The results show that the larvae begin to feed on 4th day after hatching, and the mixed nutrition stage lasts for 3 d. The larvae come into endogenous nu- trition stage at 7th day, in which the yolk-sac is absorbed completely. The initial larval feeding rate reaches only 15% at the beginning and 100% at 6th day, but decreases rapidly since 9th day. The PNR occurres at 9＇h - 10＇h day after hatching. The survival is not obvi- ously affected by delaying initial feeding for 1 -3 d but drops significantly when the delay is more than 4 d. Under absolutely hungry condition, the total length of the larvae has positive growth in 0 - 8 d but then changes to negative growth. The difference is not signifi- cant in the total length of the larvae （12-day old） delayed initial feeding for 1 -3 d （P〉0. 05）, but is very significant when the delay is more than 4 d （P 〈0. 01 ）. The optimum initial feeding time for the larvae is within 3 d after their mouths open.