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

9319843汤森德这个项目将调查在春季和初夏形成热层结期间乔治斯浅滩鳕鱼幼体的“分布史”。温度层积期是幼体垂直和区域分布错综复杂可能对存活和最终招募产生重要影响的时期。该项目将利用最近开发的耳石分析新技术(锶/钙比)来预测乔治斯浅滩地区在不同水文状况下收集的单个鳕鱼幼体的温度历史，因此也就是分布历史(即从孵化到捕获)。这项技术将通过采用一种新技术--电子能量损失光谱学来推进，它将把锶/钙技术的分辨率提高到能够分辨次日温度历史的水平。这些分析可以揭示进入或穿过温跃层的地底垂直迁移。幼体鳕鱼被认为与乔治河岸两侧的分层水域比岸顶的潮汐混合水域更密切地联系在一起，并随着残余循环被输送到乔治海岸周围并向西南方向输送。在初春，它们的浮游动物猎物在热锋的层状一侧也更丰富，幼虫往往与温跃层中最大猎物丰度的深度有关。在当年晚些时候，后期幼体和早期幼体在岸顶，那里的浮游动物密度变得比侧翼更大。幼虫在混合和分层水域的垂直和区域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检查鳕鱼幼体的分布，并将与一项已获资助的研究(NOAA)形成合作联系，该研究重点是春季层化过程的物理，因为它与整个浮游动物系列有关，以及鳕鱼和黑线鳕幼体的分布、生长和状况，从而形成一个强有力的跨学科计划。***

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. ***