Climate warming and high salmon migration mortality

太平洋鲑鱼支撑着加拿大西部最有价值的商业和休闲渔业，每年产生超过10亿美元的收入。它们是食物链的重要组成部分，是太平洋沿岸第一民族神话、精神完整性和当地经济的组成部分，也是公众的象征，大量的鲑鱼证实了健康和原始的环境。大多数太平洋鲑鱼在上游产卵迁徙中遇到的河流比有记录以来的任何时候都要温暖。弗雷泽河是加拿大鲑鱼产量最高的河流，在过去10年里经历了8次有记录以来最热的夏季水温，气候模型预测在不久的将来温度会更高。与高温相关的是高水平的洄游死亡率，数百万鱼在洄游过程中消失或未产卵就死亡，给渔业造成了巨大损失。这种现象构成了严重的保护风险，并使弗雷泽红眼的可持续性受到质疑。新政策已将捕捞红鲑鱼的地点从凉爽的海洋转移到温暖的河流，如果它们逃脱或被释放，将面临双重危险，因为在高温下挣扎可能导致释放后数小时死亡。我们将开展实验，建立可预测预期热暴露和与不同水平的非滞留河内捕捞相互作用的死亡率的标准，并评估成虫洄游热暴露对卵和后代的影响。我们的研究结果将提供重要的信息，用于帮助渔业管理机构，我们在这个项目中的合作伙伴，他们的任务是预测迁徙死亡率，预测未来的种群规模，管理栖息地以保护资源。

Pacific salmon support the most valuable commercial and recreational fisheries in western Canada generating over $1 billion of revenue annually. They are an important component of the food chain, are integral to mythology, spiritual integrity, and local economies of Pacific coast First Nations, and are icons for the general public, with abundant salmon confirming healthy and pristine environments. Most stocks of Pacific salmon now encounter warmer rivers during their up-river spawning migration than in any time since records were kept. The Fraser River is Canada's most productive salmon system and has experienced in the past 10 years eight of the hottest summer water temperatures on record, and climate models predict even warmer temperatures in the near future. Associated with these high temperatures have been high levels of migration mortality costing the fishery significantly with millions offish disappearing during migrations or dying unspawned. This phenomenon constitutes a severe conservation risk and puts the sustainability of Fraser sockeye in doubt. New policies have shifted sockeye salmon harvesting from cool ocean to warm river locations which puts salmon in double jeopardy if they escape or are released from capture because struggling under high temperatures can lead to mortality hours after release. We will conduct experiments to establish criteria which can predict mortality rates from expected thermal exposure and interactions with different levels of non-retention in-river fishing, and to assess effects of adult migratory thermal exposure on eggs and offspring. Our findings will provide important information that will be used to help the fisheries management agencies, our partners in this project, with their task of predicting migration mortality, predicting future stock sizes, and managing habitat to conserve the resource.