Distribution and Survival of Cod Larvae in Relation to Hydrography on Georges Bank

这个项目将在热分层形成的春季和初夏期间调查乔治河岸鳕鱼幼虫的“分布历史”。在热分层时期，幼虫的垂直和面积分布的复杂性可能对生存和最终招募具有重要意义。该项目将利用最近发展起来的耳石分析新技术（Sr/Ca比值）来预测在乔治海岸地区不同水文条件下收集的单个鳕鱼幼虫的温度历史，从而预测其分布历史（从孵化到捕获）。该技术将通过采用一种新技术——电子能量损失光谱（electron energy loss spectroscopy）来推进，该技术将把Sr/Ca技术的分辨率提高到能够分辨亚日温度历史的水平。这些分析可以揭示dieel垂直迁移进入或通过温跃层。据信，幼鳕鱼与乔治海岸两侧的分层水域比与海岸顶部的潮汐混合水域关系更密切，并随剩余环流在乔治海岸周围和西南方向运输。它们的浮游动物猎物丰度在早春热锋的分层侧也更丰富，并且幼虫通常与温跃层中最大猎物丰度的深度有关。在一年中的晚些时候，晚期的幼虫和早期的幼鱼在浅滩的顶部，那里的浮游动物密度比侧翼的要大。在混合和分层水域中，幼虫垂直和面积分布的确切性质可能对水平运输过程、温度对生长的影响以及浮游动物猎物的可获得性非常重要。该项目将采用新技术来检查鳕鱼幼虫的分布，并将与一项已经获得资助的研究（美国国家海洋和大气管理局）形成合作关系，该研究侧重于春季分层过程的物理学，因为它涉及到整套浮游动物，以及鳕鱼和黑线鳕幼虫的分布、生长和状况，从而形成一个强大的跨学科项目。* * *

9319843 Townsend This project will investigate the "distributional histories" of larval cod on Georges Bank during the spring and early summer period of developing thermal stratification. The period of thermal stratification is a time during which the intricacies of larval cod vertical and areal distributions may hold important implications for survival and ultimately recruitment. This project will utilize a new technique of otolith analyses (Sr/Ca ratios), which has recently been developed, to hindcast the temperature histories, and hence distributional histories (that is from the time of hatching to capture), of individual cod larvae collected in various hydrographic regimes in the Georges Bank area. The technique will be advanced by employing a new technology, electron energy loss spectroscopy, which will increase the resolution of the Sr/Ca technique to a level capable of resolving sub-daily temperature histories. These analyses could reveal diel vertical migrations into or through a thermocline. Larval cod are believed to be more closely associated with the stratified waters on the sides of Georges Bank than the tidally mixed waters on top of the Bank, and are transported around Georges Bank and to the southwest with the residual circulation. The abundances of their zooplankton prey are also more abundant on the stratified side of the thermal front in early spring, and the larvae are often associated with the depth of maximum prey abundance in the thermocline. Later in the year the late larvae and early juveniles are on the top of the Bank, where zooplankton densities become greater than on the flanks. The exact nature of the vertical and areal distributions of the larvae in relation to mixed and stratified waters may be very important with regard to horizontal transport processes, temperature effects on growth, and the availability of zooplankton prey items. This project will employ new technology to examine the distributions of cod larvae a nd will form a collaborative link with an already-funded study (NOAA) that focuses on the physics of the vernal stratification process as it relates to the complete suite of zooplankton, and the distribution, growth and condition of cod and haddock larvae, thus making for a strong interdisciplinary program. ***