以‘吉富’、‘新吉富’、‘埃及尼罗’3种不同品系尼罗罗非鱼(Oreochromis niloticus)为研究对象, 通过不同品系之间生长与高密度胁迫反应的比较, 探讨3种尼罗罗非鱼的生长特点与应激后生理响应的变化规律。将初始规格基本一致的3种品系尼罗罗非鱼饲养100 d后, 吉富罗非鱼特定生长率最高, 新吉富其次, 两者间无显著差异(P>0.05), 埃及尼罗罗非鱼特定生长率显著低于吉富罗非鱼(P<0.05)。吉富与新吉富罗非鱼的内脏比显著高于埃及尼罗(P<0.05); 3种尼罗罗非鱼的肥满度之间无显著差异(P>0.05)。养殖实验结束后, 进行48 h的急性高密度(100 g/L)应激实验。应激48 h内, 吉富与新吉富罗非鱼血清总蛋白、葡萄糖、谷草转氨酶、胆固醇与溶菌酶活力/水平以及肝HSP70mRNA水平呈先上升后下降的变化。应激48 h后, 埃及尼罗罗非鱼血清皮质醇水平与应激前相比无显著差异(P>0.05), 吉富与新吉富罗非鱼的皮质醇水平显著高于应激前(P<0.05); 埃及尼罗罗非鱼血清溶菌酶活力与肝HSP70 mRNA水平在应激后48 h内始终高于应激前(P<0.05)。研究结果表明, 短期高密度胁迫可提高3种尼罗罗非鱼血清葡萄糖与甘油三酯的利用, 并诱发肝损伤。埃及尼罗罗非鱼的抗高密度应激能力高于吉富和新吉富罗非鱼。

To establish the growth performance and physiological responses after short-term crowding stress, three Nile tilapia (Oreochromis niloticus) strains (GIFT tilapia, new GIFT tilapia and Egypt Nile tilapia) were compared in terms of certain body indices. At day 100 of the experiment, tilapias in the experimental group were exposed to short-term crowding stress to evaluate the serum biochemical parameters and liver HSP70 mRNA expression before and after stress. The results showed that GIFT tilapia had the best growth rate, and the growth of New GIFT tilapia ranked second; however, no significant difference was observed between the two strains. The growth rate of Egypt Nile tilapia was the slowest. Viscerosomatic indices of GIFT tilapia and New GIFT tilapia were significantly higher than those of the Egypt Nile tilapia. There was no significant difference in the condition factor among the three groups. At the end of the feeding trial, 40 fish per bucket were exposed to crowding stress (100g/L) for 48h, The effects of a short-term exposure on the physiological responses of fish were determined before stress (0h) and at 6, 12, 24 or 48 h post-crowding. The serum total protein, glucose, glutamic-oxaloacetic transaminase (AST), cholesterol, lysozyme (LSZ) level and hepatic Hsp70mRNA levels in GIFT tilapia and New GIFT tilapia initially increased and then decreased over48 h of crowding stress. Compared with the level at 0 h, the serum cortisol level of the Egypt Nile tilapia was not significantly difference at 48 h post-stress, but the levels in GIFT tilapia and New GIFT tilapia were significantly higher than at 0h. The serum LSZ activity and HSP70 mRNA levels of the Egypt Nile tilapia at 48 h were significantly higher than at 0 h. Overall, the results indicated that short term, high density crowding enhanced the use of serum glucose and triglyceride, but caused liver damage in tilapia. The ability of the Egypt Nile tilapia to resist high density stress is stronger than that of the GIFT tilapia and New GIFT tilapia. Therefore, for intensive culture farming, tilapia should have a reasonable stocking density and less human interference, which will reduce stress responses and promote healthy breeding of tilapia.