Identifying mechanisms leading to size-selective mortality in the early marine phase of juvenile Pacific salmon

确定导致幼年太平洋鲑鱼早期海洋阶段尺寸选择性死亡的机制

• 批准号: RGPIN-2014-06229
• 负责人: Juanes, Francis
• 金额: $ 2.48万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=654901
• 关键词: Identifying; mechanisms; leading; size; selective

Many stocks of Pacific salmon are experiencing continued and severe declines despite reductions in fishing effort and the implementation of conservation and mitigation initiatives. This prolonged decline of salmon stocks is particularly prevalent in Chinook salmon and sockeye salmon, where declines have been observed range-wide, but especially in southern BC. The sustained low return rates of southern British Columbia salmon stocks over the last 20 years have been attributed to a combination of unfavorable marine conditions during early life such as climate change, variability in prey availability, predation risk, disease, habitat degradation, or human stressors other than fishing. While the causes of Pacific salmon declines are likely multifactorial, it is generally recognized that persistently unfavourable ocean conditions and poor marine survival played a major role in these declines. Salmon mortality rates generally exceed 90-95% during the marine stages of their life. Much of this loss is thought to occur in coastal environments as a consequence of either heavy predation upon ocean entry and/or due to winter starvation. Here, we will take a multidisciplinary approach to elucidate the interacting effects of ocean conditions, growth, phenology, and physiological performance on variation in survival of early ocean juvenile Chinook and sockeye salmon. **Specific objectives include: 1/ Quantifying the links between early growth and mortality by assessing the role of early marine growth and condition to survival of juvenile salmon from otolith microstructure, length frequency analyses, and energy dynamics; 2/ Experimentally testing how juvenile salmon respond to climate and food variability during early marine life; 3/ Testing the relationship between winter severity and resiliency to starvation on growth, survival, and vulnerability to predation as a function of size; and 4/ Quantifying energetic levels, stress indicators, parasite loads and diversity, and building genomic profiles related to stress conditions. **Our general hypotheses include: 1/ Variability in the timing, size at entry, and early of growth of salmon entering the marine environment will be correlated to size before winter and survival. Earlier entry may match earlier climate-change induced spring blooms leading to increased growth rates and higher survival. And, faster growing individuals should exhibit less size-selective mortality. The outcome of the interplay between phenology and growth will depend on conditions such as temperature and food availability, which we will test experimentally; 2/ Lipid levels will increase with body size, vary with temperature and ration, but generally decline through the winter; 3/ We predict that food limitation and/or low growth will increase vulnerability to predation due to differences is risk-taking behaviour; and 4/ We predict strong responses to temperature extremes and low food rations. Under these conditions growth and lipid accumulation should be reduced, stress levels increased, parasite loads and diversity elevated, aggressive behavior more common, and vulnerability to predation increased. In addition we expect that those genes coding for proteins related to thermal and food deprivation stress such as heat shock proteins and growth hormone receptors will vary across tissues and treatments.**Our results will provide missing information needed to evaluate when and where early marine mortality is acting, the extent of size selectivity, and the potential mechanisms responsible for the observed mortality. By assessing the extent and causes of early marine mortality in juvenile salmon, this project will improve our understanding of the factors limiting the production of Pacific salmon in the marine environment.

尽管减少了捕捞努力量，并实施了养护和减缓举措，但许多太平洋鲑鱼种群仍在持续严重减少。鲑鱼种群的这种长期下降在奇努克鲑鱼和红鲑鱼中特别普遍，在那里观察到了广泛的下降，但特别是在BC省南部。在过去的20年里，南不列颠哥伦比亚省鲑鱼种群的持续低回报率归因于早期生活中不利的海洋条件，如气候变化，猎物可用性的变化，捕食风险，疾病，栖息地退化，或人类的压力，而不是捕鱼。虽然太平洋鲑鱼数量减少的原因可能是多方面的，但人们普遍认为，持续不利的海洋条件和海洋生存状况不佳是造成鲑鱼数量减少的主要原因。鲑鱼的死亡率在其生命的海洋阶段通常超过90-95%。 据认为，这种损失大部分发生在沿海环境中，这是由于进入海洋后的严重捕食和/或冬季饥饿造成的。 在这里，我们将采取多学科的方法来阐明海洋条件，生长，物候和生理性能的变化早期海洋青少年奇努克和红鲑生存的相互作用的影响。 ** 具体目标包括：1/通过从耳石微结构、长度频率分析和能量动力学评估早期海洋生长和条件对幼鲑生存的作用，量化早期生长和死亡率之间的联系; 2/实验测试幼鲑如何在早期海洋生命期间对气候和食物变异作出反应; 3.测试冬季严酷性和对饥饿的恢复力对生长、存活和对捕食的脆弱性之间的关系，作为大小的函数;和4/量化能量水平、压力指标、寄生虫负荷和多样性，并建立与压力条件相关的基因组图谱。** 我们的一般假设包括：1/鲑鱼进入海洋环境的时间，大小和早期生长的变化将与冬季前的大小和生存相关。较早的进入可能与较早的气候变化引起的春季开花相匹配，从而提高生长率和存活率。 而且，生长较快的个体应该表现出较小的尺寸选择性死亡率。 物候和生长之间相互作用的结果将取决于温度和食物供应等条件，我们将通过实验进行测试; 2/脂质水平将随着身体大小而增加，随温度和口粮而变化，但通常在冬季下降; 3/我们预测食物限制和/或低生长将增加由于冒险行为差异而对捕食的脆弱性; 4/我们预测对极端温度和低食物配给的强烈反应。 在这些条件下，生长和脂质积累应减少，应力水平增加，寄生虫负载和多样性升高，侵略行为更常见，易被捕食增加。此外，我们预计编码与热应激和食物剥夺应激相关的蛋白质（如热休克蛋白和生长激素受体）的基因在组织和治疗中会有所不同。我们的研究结果将提供评估早期海洋死亡率何时何地起作用所需的缺失信息，大小选择性的程度，以及对观察到的死亡率负责的潜在机制。通过评估幼鲑鱼早期海洋死亡的程度和原因，该项目将提高我们对限制海洋环境中太平洋鲑鱼生产的因素的认识。