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.

尽管捕鱼的努力减少以及保护和缓解措施的实施，但许多太平洋鲑鱼的股票正在持续和严重下降。在奇努克鲑鱼和红鲑鱼中，鲑鱼库存的长期下降尤其普遍，在奇努克鲑鱼和鲑鱼中，范围内观察到量的下降，尤其是在卑诗省南部。在过去20年中，不列颠哥伦比亚省南部鲑鱼库存的持续较低的回报率归因于早期生命中不利的海洋状况的结合，例如气候变化，猎物供应率的可变性，捕食风险，疾病，栖息地降解或其他人的压力。尽管太平洋鲑鱼下降的原因可能是多因素的，但人们普遍认为，持续不利的海洋状况和贫困海洋生存在这些下降中起着重要作用。鲑鱼死亡率在海洋生物的阶段通常超过90-95％。 人们认为，由于海洋进入和/或冬季饥饿所致，这种损失大部分被认为是在沿海环境中发生的。 在这里，我们将采用一种多学科的方法来阐明海洋状况，生长，物候学和生理性能对早期海洋少年奇努克和红鲑鱼生存的变化的相互作用。 **特定目标包括：1/通过评估海洋生长的作用和条件对来自耳石微结构，长度频率分析和能量动力学的生存的作用来量化早期生长与死亡率之间的联系； 2/实验测试少年鲑鱼如何应对早期海洋生物的气候和食物变异性； 3/测试冬季严重程度与弹性对生长，生存和对捕食的脆弱性的关系，这是大小的函数； 4/量化能量水平，应力指标，寄生虫负载和多样性以及与应力条件相关的基因组谱。 **我们的一般假设包括：1/进入海洋环境的鲑鱼的时间，进入时的大小以及鲑鱼的早期生长将与冬季和生存之前的大小相关。较早的进入可能与早期的气候变化诱发的春季开花相匹配，从而增加增长率和更高的生存率。 而且，更快的人应表现出较少的尺寸选择死亡率。 物候与生长之间相互作用的结果将取决于温度和食品供应等条件，我们将通过实验进行测试。 2/脂质水平随体型而增加，随温度和评分而变化，但整个冬季通常会下降； 3/我们预测，由于差异而导致的粮食限制和/或低增长将增加对捕食的脆弱性是冒险行为； 4/我们预测对极端温度和低食物评估的强烈反应。 在这些条件下，应降低生长和脂质积累，应力水平增加，寄生虫负荷和多样性提高，攻击性行为更普遍，并且捕食的脆弱性增加。此外，我们希望那些编码与热休克蛋白和生长激素受体等蛋白质相关的蛋白质的基因在组织和治疗中会有所不同。通过评估少年鲑鱼早期海洋死亡率的程度和原因，该项目将提高我们对限制海洋环境中太平洋鲑鱼产量的因素的理解。