Summer surveys of the Chukchi Sea indicate that high densities of age‐0 gadid fishes, historically Arctic cod (Boreogadus saida) but recently also walleye pollock (Gadus chalcogrammus), dominate the pelagic fish community. Adults are comparatively scarce, suggesting that either overwinter survivorship of age‐0 gadids is low, or that they emigrate to other areas of the Pacific Arctic. To examine population movement, we conducted repeat acoustic surveys with saildrone autonomous surface vehicles equipped with echosounders throughout summer 2018. The saildrones' range and endurance enabled two large‐scale surveys of the U.S. Chukchi shelf. Acoustic backscatter, a proxy for fish density, was highest in regions with sea surface temperatures of 6–8°C, and lowest in areas influenced by recent ice melt. A subarea of the central Chukchi was surveyed a total of four times; backscatter in this subarea increased by > 85% from late‐July to mid‐September. As summer progressed, fish developed more extensive diel vertical migrations and backscatter from individuals doubled. Both changes suggest increases in backscatter were driven primarily by increasing body size. Particle tracking simulations indicated age‐0 gadids were likely retained over the Chukchi shelf by extended periods of wind‐driven southward flow during the survey period before strong northward flow in late fall transported them to the north. These findings suggest that in summer 2018, age‐0 gadids were advected northward to the Chukchi shelf from the northern Bering Sea, where they were retained during a period of growth until late fall before being advected farther north toward the Chukchi and Beaufort shelf breaks.

中文翻译：

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自主车辆调查表明，流量逆转将幼鱼保留在高度对流的高纬度生态系统中

楚科奇海的夏季调查表明，高密度的0岁年龄游adi鱼类，从历史上讲是北极鳕（Boreogadus saida），但最近也有白wall（Gadus chalcogrammus）。），主导中上层鱼类群落。成虫相对稀少，这表明要么0岁年龄组的越冬生存率很低，要么他们移民到了太平洋北极地区。为了检查人口流动，我们在整个2018年夏季对配备了回声测深仪的Saildrone自主地面车辆进行了重复的声学调查。Saildrones的射程和耐久度使美国Chukchi架子得以进行两次大规模调查。声学反向散射是鱼类密度的代表，在海表温度为6-8°C的地区最高，而在最近受冰融化影响的地区最低。楚科奇地区的一个分区共进行了四次调查。从7月下旬到9月中旬，该分区的反向散射增加了85％以上。随着夏天的发展，鱼类的diel垂直迁移更为广泛，个体的反向散射增加了一倍。两种变化都表明，后向散射的增加主要是由于身体尺寸的增加所致。粒子跟踪模拟表明，在调查期间，风吹南下的时间延长了，楚科奇陆架上可能保留了0岁年龄的小行星，而深秋的北向气流则将它们运到了北部。这些发现表明，在2018年夏季，从白令海北部向北向楚克奇陆架平移了0岁的gadds，在生长期间一直保留到秋末，然后才向北向楚克奇和博福特陆架断裂平移。粒子跟踪模拟表明，在调查期间，风吹南下的时间延长了，楚科奇陆架上可能保留了0岁年龄的小行星，而深秋的北向气流则将它们运到了北部。这些发现表明，在2018年夏季，从白令海北部向北向楚克奇陆架平移了0岁的gadds，在生长期间一直保留到秋末，然后才向北向楚克奇和博福特陆架断裂平移。粒子跟踪模拟表明，在调查期间，风吹南下的时间延长了，楚科奇陆架上可能保留了0岁年龄的小行星，而深秋的北向气流则将它们运到了北部。这些发现表明，在2018年夏季，从白令海北部向北向楚克奇陆架平移了0岁的gadds，在生长期间一直保留到秋末，然后才向北向楚克奇和博福特陆架断裂平移。