密度胁迫对点带石斑鱼幼鱼生长、代谢的影响

Effects of density stress on growth and metabolism of juvenile Epinephelus malabaricus

点带石斑鱼(Epinephelus malabaricus)幼鱼体质量(15±0.5)g,将其随机分为4组,每缸(直径60cm×水深50cm)分别放养10尾、20尾、30尾、40尾幼鱼,密度分别相当于1.1kg/m3、2.1kg/m3、3.2kg/m3、4.2kg/m3,并分别标记记为G10、G20、G30、G40,每组3个重复,养殖6周后对幼鱼进行生长性能、饲料系数、血液指标及肝脏中相关酶活性进行分析以研究密度胁迫对点带石斑鱼幼鱼生长、代谢的影响。结果表明:1)G10组幼鱼增重率显著低于其他各组(P<0.05),G20组增重率最高且显著高于其他组(P<0.05)。各组间特定生长率的变化与增重率的变化趋势类似。G10和G20组的饲料系数显著低于G30组(P<0.05),G40组饲料系数最高且显著高于其他各组(P<0.05)。2)G30和G40组间血浆皮质醇含量无显著差异(P>0.05),但均显著高于G10和G20组(P<0.05),G10组皮质醇含量显著低于G20组(P<0.05)。血糖含量呈现与皮质醇含量相同的变化趋势。3)G30和G40组谷丙转氨酶活性均显著高于G10和G20组(P<0.05),各组谷草转氨酶活性随养殖密度的升高而升高;G40组乳酸脱氢酶活性最高,与G30组无明显差异(P>0.05),但G40与2个低密度组(G10和G20)差异显著(P<0.05);乙酰胆碱酯酶活性随养殖密度的升高而降低。结果表明,养殖密度过高或过低都会对点带石斑鱼幼鱼的生长与代谢造成负面影响,20尾/缸(2.1kg/m3)是较为适宜的养殖密度。本研究旨在为工厂化养殖点带石斑鱼提供理论依据。

A 6-week feeding trail was conducted to study the effect of density stress on growth performance,plasma cortisol,blood glucose and activities of related enzymes of juvenile Elineophelelus malabaricus.Three hundred juveniles,body weight （15±0.5） g were randomly distributed in 4 experimental groups：G10 （10 ind/tank,1.1 kg/m 3）,G20 （20 ind/tank,2.1 kg/m 3）,G30 （30 ind/tank,3.2 kg/m 3）,and G40 （40 ind/tank,4.2 kg/m 3）.The results showed：（1） weight gain （WG） and specific growth rate （SGR） of G10 were the lowest among the experimental groups,and WG and SGR of G20 were the highest.Feed conversion ratio （FCR） increased with the increase of density.（2） No significant difference was observed in plasma cortisol levels between G30 and G40 （P 0.05）,plasma cortisol levels of G10 and G20 were significantly lower than those of G 30 and G 40 （P 0.05）,and plasma cortisol level of G10 was the lowest.Similar trend was recorded in blood glucose levels.（3）Glutamic pyruvic transaminase （GPT） activities of G30 and G40 were significantly higher than those of G10 and G20 ;glutamic oxaloacetic transaminase （GOT） activities and lactic dehydrogenase （LDH） activities increased with the increase of the stocking density,total choline esterase （TChE） activities decreased with the increase of the stocking density.Hence,too high or too low stocking density would affect the growth performance and metabolism of juvenile Epinephelus malabaricus,and 20 ind/tank （2.1 kg/m3） was considered to be a suitable stocking density.