EFFECTS OF DELAYED FIRST FEEDING ON GROWTH,SURVIVAL AND BIOCHEMICAL COMPOSITION OF CROAKER MIICHTHYS MIIUY LARVAE

Effects of the timing of first feeding (3,4,5,6 dah and no fed) on the feeding growth,survival and biochemical composition of croaker Miichthys miiuy larvae were investigated at 24℃under laboratory conditions.The larvae started to open mouth and started feeding on 3 days after hatching (dah).Yolk absorption was completed on 4 dah and the larvae reached PNR or irreversible starvation age on 6 dah (2d after yolk exhaustion).Larvae first fed on 3 and 4 dah (15%—16%) survived apparently better than those fed on 5 dah (9%) at the end of the experiment (36dah).High larval mortality occurred from first feeding time to 7 dah in all treatments,accounting for 40% (first fed prior to 5 dah larvae) to 90% (first fed on 6 dah and no fed larvae) of the total mortality throughout the experiment.No larvae first fed after 5 dah could survive to 8dah.Larvae first fed on 3 and 4 dah had apparently better growth performance (SGR=5%) than those first fed on 5 dah (4%).Similarly,the individual size variation (CV of the final L_t) of the larvae decreased from 13—15 in the former two groups to 11 in the latter ones.However,neither larval survival nor growth showed noticeable differences between the 3 and 4 dah feeding groups.On 36dah,the percentages of either crude protein or lipid of the larvae body had no significant difference among the 3,4,and 5 dah feeding groups.These results indicate that delayed first feeding up to ld after yolk absorption could lead to adverse survival and growth of croaker larvae but showed negligible influences on the nutritional status of the survivors.To avoid potential starvation mortality for better growth, feeding the larvae should be started within ld after yolk absorption at 24℃.