Climate-driven changes in the oceans, such as shifts in prey timing and abundance, could influence variability in population productivity of marine fishes. For example, according to the match-mismatch hypothesis, the temporal matching of the young salmon outmigration from freshwater to the ocean relative to the timing of availability of their prey could influence their marine survival. Indeed, understanding patterns and processes of marine survival is particularly pressing in many salmon and steelhead trout populations due to recent declines. To determine whether phenological mismatches between juvenile salmonids and their prey could contribute to low ocean survival, we analyzed the migration timing and ocean survival of 22,116 tagged juvenile steelhead trout Oncorhynchus mykiss over 12 years from the Wind River, Washington State, USA. We used a Bayesian multilevel modelling approach with variable selection to assess how survival was associated with body size, river exit date, the biological spring transition date (the day when northern zooplankton first appeared in the coastal region near the Columbia River estuary), and the degree of mismatch (the effect of the interaction between individual outmigration timing and biological spring transition date). The variables with the highest probability of contributing to individual survival were fish size (100%), river exit date (99%), the interaction between year and river exit date (91%), and the biological spring transition date (64%). Fish that were larger than average at outmigration had higher ocean survival, providing further evidence that freshwater growing conditions have carryover effects on marine survival. Years with greater annual phenological mismatches such as those years with late biological spring transition dates (i.e. occurring after June 1^st), or warm sea surface temperatures, had sufficiently low marine survival to compromise recovery goals. Substantial intra-annual variation in outmigration timing buffered the population from inter-annual variation in optimal outmigration timing. Collectively these findings indicate that freshwater growing conditions, migration timing, and the timing of high-quality food availability in the nearshore coastal environment work in concert to influence individual survival and annual smolt-to-adult returns.

由海洋引起的气候变化，例如猎物时机的变化和丰度的变化，可能会影响海水鱼类种群生产力的变化。例如，根据匹配不匹配假说，年轻鲑鱼从淡水向海洋的迁移与它们猎物的可获得时间的时间匹配可能会影响其海洋生存。的确，由于最近的下降，了解鲑鱼和硬头鳟鳟鱼种群对海洋生存的方式和过程的要求尤其迫切。为了确定幼鲑鱼及其猎物之间的物候学失配是否可能导致低海洋生存率，我们分析了22,116个带标签的幼年虹鳟鳟鱼Oncorhynchus mykiss的迁移时间和海洋生存从美国华盛顿州的风河出发超过12年。我们使用带有变量选择的贝叶斯多级建模方法来评估生存率与体型，河流出口日期，生物春季过渡日期（北部浮游动物首次出现在哥伦比亚河河口附近的沿海地区的日期）之间的关系，以及错配程度（个体迁出时机与春季春季迁徙日期之间相互作用的影响）。对个体生存有最大影响的变量是鱼的大小（100％），河道退出日期（99％），年份与河道退出日期之间的相互作用（91％）和生物春季过渡期（64％） 。在外迁时大于平均水平的鱼类具有更高的海洋生存能力，提供进一步的证据表明淡水生长条件对海洋生存有影响。年度物候失配较大的年份，例如生物学春季过渡期较晚的年份（即发生在6月1日之后的年份）^st）或温暖的海面温度，其海洋存活率足够低，无法达到恢复目标。移民时间的年内大幅变化使人口免受最佳移民时间的年际变化的影响。这些发现共同表明，近岸沿海环境中的淡水生长条件，迁移时机和高质量食物的供应时机共同作用，影响着个体的生存和每年的成虫到成年的回报。