Midwood Jonathan D, Larsen Martin H, Aarestrup Kim, Cooke Steven J
Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6
National Institute of Aquatic Resources, Freshwater Fisheries, Technical University of Denmark, Vejlsøvej 39, Silkeborg 8600, Denmark.
J Exp Biol. 2016 Dec 1;219(Pt 23):3712-3718. doi: 10.1242/jeb.140665. Epub 2016 Sep 12.
Food deprivation is a naturally occurring stressor that is thought to influence the ultimate life-history strategy of individuals. Little is known about how food deprivation interacts with other stressors to influence migration success. European populations of brown trout (Salmo trutta) exhibit partial migration, whereby a portion of the population smoltifies and migrates to the ocean, and the rest remain in their natal stream. This distinct, natural dichotomy of life-history strategies provides an excellent opportunity to explore the roles of energetic state (as affected by food deprivation) and activation of the glucocorticoid stress response in determining life-history strategy and survival of a migratory species. Using an experimental approach, the relative influences of short-term food deprivation and experimental cortisol elevation (i.e. intra-coelomic injection of cortisol suspended in cocoa butter) on migratory status, survival and growth of juvenile brown trout relative to a control were evaluated. Fewer fish migrated in both the food deprivation and cortisol treatments; however, migration of fish in cortisol and control treatments occurred at the same time while that of fish in the food deprivation treatment was delayed for approximately 1 week. A significantly greater proportion of trout in the food deprivation treatment remained in their natal stream, but unlike the cortisol treatment, there were no long-term negative effects of food deprivation on growth, relative to the control. Overall survival rates were comparable between the food deprivation and control treatments, but significantly lower for fish in the cortisol treatment. Food availability and individual energetic state appear to dictate the future life-history strategy (migrate or remain resident) of juvenile salmonids while experimental elevation of the stress hormone cortisol causes impaired growth and reduced survival of both resident and migratory individuals.
食物匮乏是一种自然发生的应激源，被认为会影响个体最终的生活史策略。关于食物匮乏如何与其他应激源相互作用以影响洄游成功率，人们所知甚少。欧洲褐鳟（Salmo trutta）种群表现出部分洄游现象，即一部分个体洄游到海洋，而其余个体则留在其出生溪流中。这种独特的、自然的生活史策略二分法为探索能量状态（受食物匮乏影响）和糖皮质激素应激反应的激活在决定洄游物种的生活史策略和生存中的作用提供了绝佳机会。采用实验方法，评估了短期食物匮乏和实验性皮质醇升高（即腹腔注射悬浮在可可脂中的皮质醇）相对于对照组对幼年褐鳟洄游状态、生存和生长的相对影响。在食物匮乏和皮质醇处理组中，洄游的鱼较少；然而，皮质醇处理组和对照组的鱼同时开始洄游，而食物匮乏处理组的鱼洄游延迟了约1周。食物匮乏处理组中留在出生溪流中的鳟鱼比例显著更高，但与皮质醇处理组不同的是，相对于对照组，食物匮乏对生长没有长期负面影响。食物匮乏组和对照组的总体存活率相当，但皮质醇处理组的鱼存活率显著较低。食物可获得性和个体能量状态似乎决定了幼年鲑科鱼类未来的生活史策略（洄游或留居），而实验性升高应激激素皮质醇会导致留居和洄游个体的生长受损和存活率降低。
