Holt Rebecca E, Jørgensen Christian
Department of Biology, University of Bergen, PO Box 7803, 5020 Bergen, Norway.
Uni Research, PO Box 7810, 5020 Bergen, Norway.
Conserv Physiol. 2014 Nov 4;2(1):cou050. doi: 10.1093/conphys/cou050. eCollection 2014.
Climate change influences the marine environment, with ocean warming being the foremost driving factor governing changes in the physiology and ecology of fish. At the individual level, increasing temperature influences bioenergetics and numerous physiological and life-history processes, which have consequences for the population level and beyond. We provide a state-dependent energy allocation model that predicts temperature-induced adaptations for life histories and behaviour for the North-East Arctic stock (NEA) of Atlantic cod (Gadus morhua) in response to climate warming. The key constraint is temperature-dependent respiratory physiology, and the model includes a number of trade-offs that reflect key physiological and ecological processes. Dynamic programming is used to find an evolutionarily optimal strategy of foraging and energy allocation that maximizes expected lifetime reproductive output given constraints from physiology and ecology. The optimal strategy is then simulated in a population, where survival, foraging behaviour, growth, maturation and reproduction emerge. Using current forcing, the model reproduces patterns of growth, size-at-age, maturation, gonad production and natural mortality for NEA cod. The predicted climate responses are positive for this stock; under a 2°C warming, the model predicted increased growth rates and a larger asymptotic size. Maturation age was unaffected, but gonad weight was predicted to more than double. Predictions for a wider range of temperatures, from 2 to 7°C, show that temperature responses were gradual; fish were predicted to grow faster and increase reproductive investment at higher temperatures. An emergent pattern of higher risk acceptance and increased foraging behaviour was also predicted. Our results provide important insight into the effects of climate warming on NEA cod by revealing the underlying mechanisms and drivers of change. We show how temperature-induced adaptations of behaviour and several life-history traits are not only mediated by physiology but also by trade-offs with survival, which has consequences for conservation physiology.
气候变化影响海洋环境，海洋变暖是主导鱼类生理和生态变化的首要驱动因素。在个体层面，温度升高影响生物能量学以及众多生理和生活史过程，这对种群层面及更广泛层面都有影响。我们提供了一个状态依赖能量分配模型，该模型预测了东北北极种群（NEA）大西洋鳕鱼（Gadus morhua）在气候变暖情况下，其生活史和行为的温度诱导适应性。关键限制因素是温度依赖的呼吸生理学，该模型包含了一些反映关键生理和生态过程的权衡。动态规划用于找到一种进化上最优的觅食和能量分配策略，该策略在生理和生态约束条件下使预期终身繁殖输出最大化。然后在一个种群中模拟最优策略，其中生存、觅食行为、生长、成熟和繁殖等情况会显现出来。利用当前的强迫条件，该模型再现了NEA鳕鱼的生长、年龄大小、成熟、性腺产量和自然死亡率模式。该模型预测该种群对气候变化的响应是积极的；在升温2°C的情况下，模型预测生长率会提高，渐近体型会增大。成熟年龄不受影响，但性腺重量预计会增加一倍多。对2至7°C更广泛温度范围的预测表明，温度响应是渐进的；预计鱼类在较高温度下生长更快，繁殖投资增加。还预测了一种更高风险接受度和增加觅食行为的新出现模式。我们的结果通过揭示变化的潜在机制和驱动因素，为气候变暖对NEA鳕鱼的影响提供了重要见解。我们展示了温度诱导的行为和若干生活史特征的适应性不仅由生理介导，还由与生存的权衡介导，这对保护生理学有影响。
