Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, P. O. Box 1144, Guilan, Iran.
J Fish Biol. 2009 Sep;75(4):784-96. doi: 10.1111/j.1095-8649.2009.02334.x.
The effects of acute stressors on physiological responses of juvenile great sturgeon or beluga Huso huso L. were investigated in two experiments. In the first experiment, fish were handled by placing them in containers at either low density (LD, one fish l(-1)) or high density (HD, four fish l(-1)) for 60 s. Concentrations of plasma cortisol, glucose and lactate were determined from blood collected at 0, 1, 3, 6 and 12 h after application of the stressor. Plasma cortisol concentrations increased after the disturbance in H. huso from both handling treatments, but changes were not significant. Plasma glucose rose significantly by 22.9 and 31.6% in LD and HD handling treatments, respectively, after 3 h. Significant increases in plasma lactate occurred within 1 h in both treatment groups, but that of the HD group was much higher. In the second experiment, fish were held at two different densities, LD (2 kg m(-2) tank bottom surface area) and HD (7 kg m(-2)), for 8 weeks and then subjected to an aerial emersion handling stressor in a net for 60 s; blood samples were taken before handling (resting, 0 h) and at 1, 3, 6 and 9 h after handling. Plasma cortisol increased significantly in fish from the HD treatment from 8.8 +/- 0.3 to 19.2 +/- 2.4 ng ml(-1) (mean +/-s.e.) by 1 h after stress, but post-handling changes in the LD group were not significant. Significant increases in both plasma glucose and lactate were observed by 1 h in both treatment groups, with peak levels of plasma glucose evident at 3 h [69.4 +/- 2.9 and 60.9 +/- 1.7 mg dl(-1) (mean +/-s.e.) in LD and HD groups, respectively]. Plasma glucose levels were significantly higher in the LD group than in the HD group at 3 and 6 h. Post-handling haemoglobin content increased by 1 h and white blood cell numbers were reduced by 3 and 6 h in the HD treatment group compared with resting values, but changes in these blood features in the LD group were not significant. Acute handling did not affect haematocrit in either treatment. The results suggest that H. huso is relatively resistant to handling and confinement, and could tolerate normal hatchery practices associated with aquaculture. Because changes in cortisol concentrations were relatively low compared with those in most teleosts, glucose and lactate concentrations may be more useful as stress indicators in juvenile H. huso. This study also demonstrated that prior exposure to a chronic stressor, specifically high stocking density, could alter the physiological response to subsequent acute handling in H. huso.
本研究在两个实验中探讨了急性应激源对幼龄施氏鲟（Acipenser schrenckii）和白鱀豚（Lipotes vexillifer）生理反应的影响。在第一个实验中，将鱼分别置于低密度（LD，每升 1 尾）和高密度（HD，每升 4 尾）的容器中处理 60 s。在应激源施加后 0、1、3、6 和 12 h 从血液中测定血浆皮质醇、葡萄糖和乳酸浓度。两种处理方式均引起了幼龄施氏鲟的皮质醇浓度升高，但变化不显著。在 LD 和 HD 处理中，血浆葡萄糖浓度分别显著升高了 22.9%和 31.6%，在 3 h 时升高。两组处理均在 1 h 内显著升高了血浆乳酸浓度，但 HD 组的升高幅度更高。在第二个实验中，将鱼分别在低密度（2 kg m(-2) 底层表面积）和高密度（7 kg m(-2)）下饲养 8 周，然后用网在空气中进行 60 s 的捕捞处理；在处理前（静止，0 h）和处理后 1、3、6 和 9 h 取血样。HD 处理组的皮质醇浓度在应激后 1 h 从 8.8 +/- 0.3 显著升高至 19.2 +/- 2.4 ng ml(-1)（均值 +/- s.e.），而 LD 组的变化不显著。两组处理均在 1 h 内显著升高了血浆葡萄糖和乳酸浓度，LD 和 HD 组的血浆葡萄糖浓度峰值出现在 3 h[分别为 69.4 +/- 2.9 和 60.9 +/- 1.7 mg dl(-1)]。在 3 和 6 h 时，LD 组的血浆葡萄糖浓度显著高于 HD 组。与静止值相比，HD 组的血红蛋白含量在处理后 1 h 增加，白细胞数量在 3 和 6 h 减少，但 LD 组的这些血液特征变化不显著。急性处理未影响两种处理的血细胞比容。结果表明，施氏鲟对捕捞和围堵具有较强的抵抗力，可以耐受与水产养殖相关的常规养殖操作。与大多数硬骨鱼类相比，皮质醇浓度的变化相对较低，因此葡萄糖和乳酸浓度可能是幼龄施氏鲟应激的更有用的指标。本研究还表明，先前暴露于慢性应激源，特别是高密度养殖，可能会改变幼龄白鱀豚对随后急性捕捞的生理反应。
