Plankton effect on forage fish production in the Northwest Atlantic

枯竭的海洋生态系统数量众多，代表着世界海洋巨大的未实现渔业生产力。在西北大西洋，尽管暂停了20年的捕捞，但大西洋的多种鳕鱼资源仍然没有恢复。与1990年代初纽芬兰沿海水域鳕鱼和其他底层鱼的崩溃不谋而合的是，传统上占成年鳕鱼饲料50%-60%的小型饲料鱼海豚的数量也迅速下降，并稳定在低水平。饲料鱼产量的持续缺乏被认为是阻碍底层鱼类种群恢复的一个重要因素，与其他亚北极海洋的动态相比，这是反常的。对于大多数海鱼来说，Capelin的补充取决于它们的幼体和幼体的存活。早期生命的存活率在很大程度上取决于初露出的幼虫和它们的浮游动物猎物的共存。在纽芬兰沿海水域，浮游动物的长期数据显示，海豚的减少与主要的桡足类物种的丰度减少相吻合。我的研究计划旨在了解幼虫的摄食生态，以测试“浮游生物效应”的假说，以维持低水平的Capelin的早期存活和招募，从而限制底层鱼类的恢复。具体目标包括：(1)量化幼海豚饮食的生活史变化，并描述首选猎物可获得性的年际波动的影响；(2)确定将猎物可获得性、摄食成功和幼体生长联系起来的功能反应关系；(3)利用渔业声学评估幼体幸存者的丰度和分布；以及(4)建立幼体生长模型，以预测在各种环境条件下的存活。由于Capelin在向大西洋鳕鱼等大型脊椎动物捕食者转移能量方面发挥关键作用，并可能限制底层鱼类种群的恢复，这项关于次级生产和幼体存活之间联系的研究将通过量化影响加拿大一些最具社会和经济重要性的渔场目前低生产力的机制来填补一个关键的知识空白。将开发的数值模型将有助于预测这些重要的海洋生态系统对未来气候趋势的反应，从而使业界、管理人员和政策制定者了解推动西北大西洋食物网生物生产和渔业产量的主要因素。

Depleted marine ecosystems are numerous and represent tremendous unrealized fisheries productivity in the World Ocean. In the Northwest Atlantic, multiple Atlantic cod stocks have still not recovered despite twenty years of fishing moratoria. Coincident with the collapse of cod and other groundfish in coastal Newfoundland waters during the early 1990s, populations of capelin, a small forage fish that traditionally contributed 50-60% of adult cod diet, also rapidly declined and stabilized at low levels. This continued lack of forage fish production, considered an important factor preventing the recovery of groundfish populations, is anomalous in comparison to the dynamics of other sub-Arctic seas. As for most marine fish, recruitment of capelin depends on the survival of their larvae and juveniles. Survival rates during early life are largely determined by the co-occurrence of emerging larvae and their zooplankton prey. In Newfoundland coastal waters, long-term zooplankton data revealed that the decline of capelin coincided with reduced abundance of dominant copepod species. My research program aims at understanding larval feeding ecology to test the hypothesis of a "plankton effect" maintaining early survival and recruitment of capelin at low levels, thereby limiting groundfish recovery. Specific objectives include: (1) quantifying life history shifts in diet of young capelin and characterizing the effects of interannual fluctuations in the availability of preferred prey; (2) determining the functional response relationships linking prey availability, feeding success and growth of larvae; (3) assessing the abundance and distribution of juvenile survivors using fisheries acoustics, and (4) modeling larval growth to predict survival in a wide range of environmental conditions. Since capelin play a key role in transferring energy to large vertebrate predators such as Atlantic cod and may limit the recovery of groundfish populations, this study on the links between secondary production and larval survival will fill a key knowledge gap by quantifying the mechanisms influencing the current low productivity of some of the most socially and economically important fisheries grounds in Canada. The numerical models that will be developed will help forecast the response of these important marine ecosystems to future trends in climate, and will thereby inform industry, managers and policy makers about the primary factors driving biological production and fisheries yield in Northwest Atlantic food webs.