| A series of 30-day feeding trials were conducted in tanks (70×60×50cm, 200L/each tank) to investigate the influences of dietary lipids, phospholipids, and n-3 series highly unsaturated fatty acids (n-3 HUFA ) on survival, growth, feeding rate, the digestive enzymes, body composition, and anti-stress abilities of large yellow croaker, Pseudosciaena crocea R. larvae. Results of the present study are presented as follows:1. A 30-day experiment was conducted in tanks to determine the effects of dietary lipid levels on the survival, growth, and body composition of larval Pseudosciaena crocea (12 dph, with initial average weight 1.93±0.11 mg). Five semi-purified micro-diets, containing 8.3%, 12.6%, 16.4%, 20.4%, and 24.8% lipid, were formulated. Each diet was randomly assigned to triplicate groups of tanks, and each tank was stocked with 3500 larvae. During the experiment, water temperature fluctuated from 23 to 25℃, salinity from 25‰to 28‰, and light intensity was 500–1500 lx on the water. The results showed that dietary lipid significantly influenced the survival and growth of large yellow croaker larvae. The survival of larvae fed the diet with 8.3% lipid (16.1%) was significantly lower than that of larvae fed other diets. However, no significant differences were observed in the survival rates of larvae fed the diets with 12.5%, 16.4% and 20.4% lipid levels (24.7%, 32.0% and 25.5%, respectively). Specific growth rates (SGR) significantly increased with increasing dietary lipid level from 8.3% to 16.4% (P<0.05), and then decreased. Based on survival and SGR, the optimum lipid requirement was estimated to be 17.5 and 17.4% of diet using second-order polynomial regression analysis, respectively.2. A 30-day feeding experiment was conducted in tanks to examine the effects of dietary phospholipid levels on growth, the digestive enzymes, body composition, and anti-stress abilities of larval Pseudosciaena crocea (15 dph, with initial average weight 3.36±0.10 mg, and initial average body length 6.15±0.71 mm). Five micro-diets, adding 0.0%, 2.5%, 5.0%, 7.5%, and 10.0% soybean lecithin, were formulated. Each diet was randomly assigned to triplicate groups of tanks, and each tank was stocked with 2500 larvae. The results showed that dietary phospholipid significantly influenced the survival, growth, and the main digestive enzymes (trypsin, amlyse, lipase, alkaline phosphatase, and aminopeptidase N) of large yellow croaker larvae. Carcass crude protein contents significantly increased with increasing dietary phospholipid level from 57.7% to 61.27% (P<0.05), and then decreased. On the contrary, carcass crude lipid contents significantly declined with increasing dietary phospholipid levels. And the ratios of carcass neutral lipid to carcass polar lipid significantly declined with the increase of dietary phospholipid levels. Following the feeding trials, the tolerances of larval Pseudosciaena crocea in stress factors such as declining water salinity and exposure to low dissolved oxygen significantly increased. Based on SGR, the optimum phospholipid requirement was estimated to be around 5.72% of diet.3. A 30-day feeding experiment was conducted in tanks to examine the effects of dietary lipid and n-3 HUFA levels on feeding rates, the digestive enzymes, body composition, and anti-stress abilities of larval Pseudosciaena crocea (15 dph, with initial average weight 3.36±0.10 mg, and initial average body length 6.15±0.71 mm). Five micro-diets, containing different lipid and n-3 HUFA levels, were formulated. Each diet was randomly assigned to triplicate groups of tanks, and each tank was stocked with 2500 larvae. The results showed that dietary lipid and n-3 HUFA levels significantly influenced the survival, growth, and the main digestive enzymes (trypsin, amlyse, lipase, alkaline phosphatase, and aminopeptidase N) of large yellow croaker larvae. At 18 dph, the feeding rates of fish larvae significantly increased with increasing dietary lipid and n-3 HUFA level; at 44dph, however, the feeding rates of fish larvae significantly decreased with increasing dietary lipid level and still increased with increasing dietary n-3 HUFA level. Carcass crude protein contents significantly declined with increasing dietary lipid level. On the contrary, carcass crude lipid contents significantly increased with the increase of dietary lipid levels. The proximate biochemical composition of larval body was not significantly influenced by dietary n-3 HUFA levels. Following the feeding trials, the tolerances of larval Pseudosciaena crocea in stress factors such as declining water temperature and salinity, exposure to low dissolved oxygen and air significantly increased.
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