Data for: Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration

<b>Abstract</b><br/><p>Migrating marine taxa encounter diverse habitats that differ environmentally and in foraging conditions over a range of spatial scales. We examined body (RNA/DNA, length-weight residuals) and nutritional (fatty acid composition) condition of juvenile sockeye salmon (<em>Oncorhynchus</em> nerka) in British Columbia while migrating through oceanographically variable waters. Fish were sampled in the stratified northern Strait of Georgia (NSoG); the highly mixed Johnstone Strait (JS); and the transitional zone of Queen Charlotte Strait (QCS). In 2015, body and nutritional condition were high in the NSoG but rapidly declined to reach the lowest levels in JS where prey availability was low, before showing signs of compensatory growth in QCS. In 2016, juvenile salmon had a significantly lower condition in the NSoG than in 2015, although zooplankton biomass was similar, condition remained low in JS, and no compensatory growth was observed in QCS. We provide evidence that differences in juvenile salmon condition between the two years were due to changes in the food quality available to juvenile fish. We propose that existing hypotheses about fish survival need to be extended to incorporate food quality in addition to quantity to understand changes in fish condition and survival between years.</p>

<b>摘要</b><br/><p>洄游海洋生物类群会在不同空间尺度下遭遇环境特征及觅食条件各异的多样栖息地。本研究考察了不列颠哥伦比亚省红大麻哈鱼幼鱼（Oncorhynchus nerka）在穿越海洋学特征多变水域期间的身体状况（RNA/DNA（核糖核酸/脱氧核糖核酸）比值、体长-体重残差（length-weight residuals））及营养状况（脂肪酸组成（fatty acid composition））。研究人员在分层的乔治亚海峡北部（NSoG）、高度混合的约翰斯通海峡（JS）以及夏洛特皇后海峡（QCS）的过渡带对鱼类进行了采样。2015年，红大麻哈鱼幼鱼在NSoG的身体及营养状况良好，但在猎物可获得性（prey availability）较低的JS迅速下降至最低水平，随后在QCS出现补偿生长（compensatory growth）迹象。2016年，尽管浮游动物生物量（zooplankton biomass）相近，但红大麻哈鱼幼鱼在NSoG的状况显著低于2015年，其在JS的状况仍维持在低水平，且在QCS未观察到补偿生长现象。本研究提供证据表明，两年间红大麻哈鱼幼鱼状况的差异源于其可获得食物质量（food quality）的变化。我们提出，现有关于鱼类存活的假说需加以拓展，除食物数量外还应纳入食物质量因素，以理解不同年份间鱼类状况及存活的变化。</p>