Plankton effect on forage fish production in the Northwest Atlantic

枯竭的海洋生态系统数量众多，代表着世界海洋中尚未实现的巨大渔业生产力。在西北大西洋，尽管有20年的休渔期，但多种大西洋鳕鱼种群仍未恢复。20世纪90年代初，随着纽芬兰沿海水域鳕鱼和其他底栖鱼类数量的锐减，毛鳞鱼（一种小型饲料鱼，传统上占成年鳕鱼饲料的50-60%）的数量也迅速下降，并稳定在低水平。饲料鱼类生产的持续缺乏被认为是阻碍底栖鱼类种群恢复的重要因素，与其他亚北极海域的动态相比是反常的。对于大多数海鱼来说，毛蛋白的补充取决于它们的幼鱼和幼鱼的存活。生命早期的存活率在很大程度上取决于新兴的幼虫和它们的浮游动物猎物的共同出现。在纽芬兰沿海水域，长期浮游动物数据显示，毛elin的减少与优势桡足类物种的丰度减少是一致的。我的研究项目旨在了解幼虫的摄食生态学，以检验“浮游生物效应”的假设，维持早期生存和低水平的毛鳞蛋白的补充，从而限制底栖鱼的恢复。具体目标包括：(1)量化年轻毛鳞鱼饮食的生活史变化，并描述优选猎物可得性年际波动的影响；(2)确定猎物可得性、取食成功和幼虫生长之间的功能反应关系；(3)利用渔业声学评估幼鱼幸存者的丰度和分布；(4)模拟幼虫生长以预测在广泛环境条件下的生存。由于毛鳞蛋白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着关键作用，并可能限制底栖鱼类种群的恢复，因此，通过量化影响加拿大一些最具社会和经济意义的渔场当前低生产力的机制，这项关于二次生产和幼虫存活之间联系的研究将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，从而将向工业界、管理人员和政策制定者提供有关西北大西洋食物网生物生产和渔业产量驱动因素的信息。

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.