Effects of substitution of live prey by microdiet on growth, survival and activities of digestive enzymes of larval Pseudosciaena crocea

A 30-day feeding experiment was conducted in tanks t o examine the effects of substitution levels of live prey (LP) by micro-diet (M D) on growth, survival, body composition and digestive enzymes of large yellow c roaker larvae, Pseudosciaena crocea. Five treatments with microd iet replacing 0% (0% MD), 25% (25% MD), 50% (50% MD), 75% (75% MD) and 100% (100 % MD) of live prey, were used. Each treatment was randomly assigned to triplicat e groups of tanks, and each tank was stocked with 3 500 larvae. The results show ed that the substitution of LP by MD significantly influenced the growth, surviv al, body composition and digestive enzymes of large yellow croaker larvae. The s pecific growth rates (SGR) of 50% MD and 75% MD were significantly higher than t hose of 100% MD (P＜0.05), and the SGR of 75% MD were significan tly higher than those of 0% MD and 25% MD (P＜0.05). However, no significant differences were observed in SGR between 50% MD and 75% MD. The cha nges of survival rates among different tested groups followed the similar patter n as that of SGRs. Carcass protein content declined with the increasing of the s ubstitution levels, and carcass protein contents of 50% MD, 75% MD and 100% MD w ere significantly lower than 0% MD and 25% MD (P＜0.05). On the c ontrary, carcass lipid content increased with the increasing of substitution lev els. The amylase specific activities of 100% MD were significantly higher than t hose of the other groups (P＜0.05), but trypsin specific activit ies were not significantly different among dietary treatments. Therefore, these results indicate that substituting 50%-75% of LP by MD after 12-day hatching in fry production of large yellow croaker is appropriate.