Climate and the ecosystem of the Arctic cod (Boreogadus saida)

在气候变化和工业化的双重压力下，北极正在迅速转变。北极鳕鱼（Boreogadus色达）在北极海域的近海生态系统中占主导地位，占公海鱼类组合的95%。一些海鸟和海洋哺乳动物，如环斑海豹（北极熊的主要猎物）、白鲸和独角鲸，主要以小型北极鳕鱼为食。因此，这一关键物种对气候变化的反应将直接影响海洋生态系统为因纽特人社区提供的服务，如传统食品、健康和服装、代际联系、艺术、狩猎收入、旅游业等。 我的团队研究北极鳕鱼的生态及其对气候变化的反应。自2003年以来，加拿大研究破冰船阿蒙森号的年度探险每年都提供进入巴芬湾，加拿大中部群岛和博福特海的机会。 船上先进的声纳不断测量这些海域中幼鱼和成鱼的分布和数量。浮游生物网和拖网被用来识别声纳探测到的鱼类。在夏季结束时，北极鳕鱼幼鱼的数量和大小特别令人感兴趣，因为它们决定了未来的种群规模。我们发现，北极鳕鱼幼鱼的生物量（数量乘以大小）在海冰破裂早期的年份很大。早期的分裂使海洋表层在夏季变暖。早期的分裂和温暖的温度可以使幼鱼生长得更快。或者，提早破壳可以让3月和4月初孵化的幼虫存活更长的时间，到夏末达到大尺寸。我们建议在未来几年内检验这些假设。我们还发现，耳石或耳石，在北极鳕鱼的定向系统的小结核，被保存在加拿大群岛的一些地区的底部沉积物。耳石记录了幼鱼的日生长和成鱼的年生长。我们建议在过去的一千年中重建的丰富和增长的北极鳕鱼在气候和冰破裂的时间相应的变化。最后，我们将测试的想法，即快速增长和相对较大的尺寸，让年轻的北极鳕鱼，以避免海鸟的捕食，通过比较耳石保留在不同的海鸟的砂囊（海鸟捕获的鱼的大小和增长的指数）的鱼与网和拖网捕获的耳石。 加拿大的因努伊特社区、活跃在北极的石油勘探部门以及政府机构（例如加拿大能源委员会、加拿大渔业和海洋部、加拿大土著和北方事务部）的决策者是通过这项研究更好地了解北极海洋生态系统对气候变化和发展的反应的最终用户。

The Arctic is transforming rapidly under the double pressure of climate change and industrialization. The Arctic cod (Boreogadus saida) dominates the offshore ecosystem of Arctic seas, making up to 95% of the fish assemblage in the open sea. Several seabirds and marine mammals such as the ring seal (the main prey of polar bear), the beluga and the narwhal, feed primarily on the small Arctic cod. Hence, the response of this pivotal species to climate change will directly impact the services provided by the marine ecosystem to Inuit communities, such as traditional food, health, and clothing, inter-generation bonding, art, hunting revenues, tourism, etc. My team study the ecology of Arctic cod and its response to variations in climate. Each year since 2003, the annual expedition of the Canadian research icebreaker Amundsen has provided access to Baffin Bay, the central Canadian Archipelago, and the Beaufort Sea. The sophisticated sonars of the ship measure continuously the distribution and abundance of juvenile and adult fish in these seas. Plankton nets and trawls are deployed to identify the fish detected by the sonars. The number and size of juvenile arctic cod at the end of the summer season are of particular interest as they dictate the future size of the population. We discovered that the biomass (number multiplied by size) of juvenile Arctic cod is large in years when the sea-ice break-up is early. An early break-up allows the surface layer of the ocean to warm up during summer. An early break-up and warmer temperatures could enable the young fish to grow faster. Alternatively, an early break-up could allow the larvae hatched early in March and April to survive with a longer time to achieve a large size by the end of summer. We propose to test these hypotheses in the coming years. We also discovered that the otoliths or ear-stones, small concretions in the orientation system of Arctic cod, is preserved in the bottom sediments of some areas of the Canadian Archipelago. The otolith records the daily growth of the young fish and the annual growth of the adults. We propose to correlate the reconstructed abundance and growth of Arctic cod over the last millennium to corresponding variations in climate and the timing of the ice break-up. Finally, we will test the idea that fast growth and a relatively large size allow young Arctic cod to avoid predation by seabirds by comparing the otoliths retained in the gizzard of different seabirds (an index of the size and growth of fish captured by seabirds) to the otoliths of the fish captured with nets and trawls. The Inuit communities of Canada, the oil exploration sector active in the Arctic, and policy makers in government agencies (e.g. Energy Board Canada; Fisheries and Oceans Canada; Indigenous and Northern Affairs, Canada) are the end users of the improved understanding of the response of arctic marine ecosystems to climate change and development generated by this research.