| 1. The effect of different incubation temperatures(16℃, 18℃, 20℃, 22℃, 24℃,28℃, and 30℃) on embryonic development of the Epinephelus moara was studied,and the stage of embryonic development after 12 hours of hatching, hatching rate, deformity rate of newly-hatched larvae were also recorded and analyzed. Newly-hatched larvae were used to carry out starvation tests and evaluate their daily survival rate and the survival activity index(SAI) at different temperature. The results showed that the embryos could be hatched at temperature between 18 ℃ and 28 ℃. Hatching time shortened with the increase of temperature, there was a very significant negative correlation between hatching time(y) and temperature(x), y=12139x-1.869, R2=0.993(P<0.01). The highest hatching rate(71.01%) and the lowest deformity rate(9.7%) were obtained at 22℃. Then the hatching rate was 65.37% with lower deformity rate(13.07%)at temperature of 20℃. The hatching rate decreased gradually when the temperature was below 22℃, and it showed as 24.39% at 18℃. And it also decreased significantly when the temperature was above 22℃ with the lowest hatching rate(16.11%) at 28℃.The variation tendency of the deformity rate of newly-hatched larvae was opposite to the hatching rate. The embryos development stopped at the stage of blastula at 16℃;when the temperature was 30℃, embryonic was no longer dividing at embryo body stage. And the change trends of SAI first increased and then decreased with the rising of the temperature. At the temperature of 20℃, SAI of the larva was the highest(25.97)with the longest half-death time of 7 d. The optimal temperature for the hatching of the fertilized eggs of E. moara was 22–24℃, and the most suitable temperature for the survival of newly-hatched larvae was 20–22℃.2. Experimental ecological approaches were applied to study the feeding habits and growth characteristics of 0-53 d larval, juvenile and young of Centropristis striata at Yantai Tianyuan Aquaculture Company. We sampled every day before the larvae were9 days old, and then, we sampled once every other day. Each sample consisting of about10~15 fish was observed under a optical microscope to observe the morphologicalcharacteristics and feeding amount, total length of fish fry can be measured with vernier caliper when they reached 10 mm. The results showed that:(1) the larvae opened its mouth in 3 days after hatching at water temperature of 24±1℃, the initial diet could be rotifer, then copepod and artemia naupliu were offered gradually with individual growth.Feeding rate of the larvae was 50%~100%, with intestinal fullness 0.99%~12.67%,feeding rate of the juvenile and the young reached 100%, and their intestinal fullness fluctuated between 2.06% and 4.21%. The feeding intensity had a distinct rhythm, with feeding peak occurred 10:00~16:00 for the larvae, and 12:00~18:00 for the juvenile and the young, little feeding behavior was observed at night.(2) The average feeding amount increased with the growth and development of fish fry, the larvae required 1.83 h to achieve satiation at 8 days old, while the 37 day’s juvenile and 48 day’s young fish needed 0.85 h and 0.67 h to get their stomach full respectively. Variation tendency of digestion time was opposite to satiation time, the larvae required required 1.75 h to get stomach totally empty at 8 days old, while the 37 day’s juvenile and 48 day’s young fish needed 2.5 h and 2.83 h for digestion respectively.(3) The relationship between feeding amount and body weight cound be described as y=4E-07x3-0.0001x2+0.033x+0.0056, R2=0.9978; between total length and day age as y=0.0003x3-0.0078x2+0.1014x+2.9337, R2=0.9936; between body weight and day age as y=0.0285e0.1904 x, R2=0.9859; between body weight and total length as y=0.4287x2-0.7138x-5.7934, R2=0.9884.3. The development of the digestive system and its associated glands was examined histologically in Centropristis striata from the first day(first day post-hatch) until 34 th day after hatching. We sampled every day before the larvae were 15 days old, with samples consisting of about 30 fish, and then, we sampled once every other day with samples consisting of about 15 fish. The newly-hatched larvae were reared in tanks and were supplied with fresh air continuously, meanwhile salinity of seawater was 30-32,and water temperature was maintained at(24±1)℃.The results suggested that yolk sac of newly-hatched larvae were huge, while the digestive tract was just a straight tube with a smooth lumen dorsally attached to the yolk sac. The mouth and the anus opened on the 3th day, and then the exogenous feeding started. There was a 4-day mixed endogenous-exogenous feeding period. Most of the yolk sac reserves were consumed quickly, during this time, prey capture began and the digestive processes continued to develop. The digestive tract of larvae was differentiated into esophagus, stomach and intestine, meanwhile the digestive glands(1iver, gall-bladder and pancreas) appeared.Yolk sac was disappeared at 7 dph, which means nutritional requirements of the larvaegradually transitioned from endogenous to exogenous. Mucous cells were present in the epitheliam of the oesophagus at 11 dph, and the number kept increasing with the development of the larval. Stomach was gradually differentiated into cardiacus, gastric body and pyloricus. At the same time, sinusoid and central veins of liver widely distributed. First gastric glands were detected at 20 dph, which indicated the beginning of digesting exogenous protein. Increased wrinkles in the mucous layer, thicker muscles,and a bigger cavity were detected in the intestine. Meanwhile, pancreas was abundant with zymogen granules,and it spread surrounding the intestine. The structure and function of digestive tract and digestive glands were gradually improved. The larval should be supplied with adequate and palatable food when they entered exogenous feeding period, and domesticated to feed formula feed after 20 dph. These findings on the development of the digestive system in Centropristis striata may lead to a better understanding of the ontogeny and would be useful to improve the larval rearing techniques of this promising Centropristis species for freshwater aquaculture diversification.4. An 9-week trial was carried out to assess the adaptation of juvenile Epinephelus moara fed diets with high energy and low nitrogen. Nine practical diets were formulated to contain three protein levels(35, 40 and 45%) and three lipid levels(9, 12 and 15%).Eight hundred and ten juvenile grouper with average initial weight 27.09 g were randomly stocked in 27 tanks(9 treatments in triplicate groups), fed diets to apparent satiation two times daily(9:00 and 16:00). The results about growth, feed utilization,body and muscle composition as well as serum biochemical parameters showed as follows: 1) Significant interaction(P<0.01) between dietary protein and lipid level were observed in weight gain(WG), specific growth rate(SGR), WG and SGR were firstly increased and then decreased with the increasing of dietary protein and lipid level, and the highest values of them(184.59% and 1.49%, respectively) were found in P40L12group; feed conversion ratio(FCR), protein efficiency ratio(PER) and feed intake(FI)reduced gradually with the increase of protein and lipid levels(P<0.05);the survival rate showed no significant difference(P>0.05)in nine treatments. 2) A positive correlation existed between body lipid content and dietary protein and lipid level, and it exhibited significant difference(P<0.01) among all the groups; muscle lipid content significant(P<0.05) affected by dietary lipid level(P<0.05), and the highest value observed in L15 group; dietary protein, dietary lipid and their interaction had nosignificant(P>0.05) effect on young Epinephelus moara of whole body and muscle. 3)A significant(P<0.05) ascent of glutamic oxalacetic transaminase activity was observed with increasing dietary lipid level, and the highest value(121.98 U/L) appeared in L15group; glutamic pyruvic transaminase activity in P45 group(89.79 U/L) was higher than that in P35 and P40 group; serum total cholesterol content positively correlated with dietary protein level, whereas they were not affected by dietary lipid level; urea nitrogen content in serum inversely correlated with protein level, and it had the highest value(1.97 mmol/L) in P35 group; dietary protein, dietary lipid and their interaction had on significant difference(P>0.05) on alkaline phosphatase, triglyceride, high-density lipoprotein and low-density lipoprotein. According to these results, a diets with 40%protein level and 12% lipid level is recommended for efficient growth of juvenile Epinephelus moara. |
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