Fish Ecology and Conservation Physiology Laboratory, Biology Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Centre for Applied Conservation Research, Department of Forest Sciences, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
Gen Comp Endocrinol. 2014 Jun 1;202:44-9. doi: 10.1016/j.ygcen.2014.04.008. Epub 2014 Apr 24.
Recent findings from iteroparous species suggest that glucocorticoid secretion following acute stress can mediate behavior and survival strategies, ultimately influencing fitness. However, these correlates of the stress response may not exist in semelparous animals given the inability to maximize fitness by delaying reproduction. We measured baseline and stress-induced cortisol concentrations in semelparous sockeye salmon (Oncorhynchus nerka) following exposure to an acute stressor at the mouth of the Fraser River in British Columbia. The homing fish were then radio-tagged and tracked throughout their in-river migration. Findings reveal that the stress response (i.e. change from baseline to stress-induced cortisol) was predictive of mortality; fish failing to leave the release site had a significantly greater stress response (mean±SE=1004.0±75.3ng/mL) compared to fish capable of successfully migrating beyond one of the most difficult areas of passage over 100 river kilometers upstream (mean±SE=780.7±66.7ng/mL). However, there were no associations between swimming behaviors, both immediately following release and to last point of detection, and the stress response. This study also introduced an unique method of tagging migrating salmon that allows for rapid capture and sampling and thus provides the first assessment of true baseline cortisol concentrations at river-entry for migrating Pacific salmon in the wild. Results show the stress response to be linked to survival in a semelparous species and therefore set the stage for further exploration into how the evolutionary theories underlying relationships between stress responsiveness and fitness may differ between semelparous and iteroparous species.
最近从多次产卵物种中得出的发现表明，急性应激后糖皮质激素的分泌可以调节行为和生存策略，最终影响适应度。然而，这些应激反应的相关性在单次产卵动物中可能并不存在，因为它们无法通过延迟繁殖来最大限度地提高适应度。我们测量了不列颠哥伦比亚省弗雷泽河口处急性应激源暴露后单次产卵的红大麻哈鱼（Oncorhynchus nerka）的基础和应激诱导的皮质醇浓度。然后，将归巢的鱼用无线电标记并在其整个河流洄游过程中进行追踪。研究结果表明，应激反应（即从基线到应激诱导的皮质醇的变化）可以预测死亡率；未能离开释放点的鱼的应激反应明显更大（平均值±SE=1004.0±75.3ng/mL），而能够成功迁移超过 100 公里上游最困难的洄游区域之一的鱼的应激反应（平均值±SE=780.7±66.7ng/mL）。然而，游泳行为与应激反应之间没有关联，无论是在释放后立即还是在最后一次检测点。本研究还引入了一种独特的标记洄游鲑鱼的方法，允许快速捕获和采样，从而首次评估了野生太平洋鲑鱼进入河流时的真实基础皮质醇浓度。研究结果表明，应激反应与单次产卵物种的生存有关，因此为进一步探讨应激反应与适应度之间关系的进化理论在单次产卵和多次产卵物种之间可能存在差异奠定了基础。
