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

乔治浅滩鳕鱼幼虫的分布和存活与水文学的关系

• 批准号: 9202061
• 负责人: David Townsend
• 金额: $ 15.34万
• 依托单位: Bigelow Laboratory for Ocean Sciences
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-01 至 1993-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9202061&HistoricalAwards=false
• 关键词: Distribution; Survival; Cod; Larvae; Relation

9202061 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. ***

9202061 Townsend 该项目将调查春季和初夏热分层发展期间乔治滩鳕鱼幼体的“分布历史”。 在热层化时期，鳕鱼幼体的垂直和区域分布错综复杂，可能对生存和最终的招募产生重要影响。 该项目将利用最近开发的耳石分析新技术（Sr/Ca 比率）来预测所收集的个体鳕鱼幼虫的温度历史，从而预测分布历史（即从孵化到捕获的时间）乔治浅滩地区的各种水文状况。 该技术将通过采用电子能量损失光谱新技术来改进，这将把 Sr/Ca 技术的分辨率提高到能够解析亚日常温度历史的水平。 这些分析可以揭示昼夜垂直迁移进入或穿过温跃层。 人们认为，与乔治浅滩两侧的分层水域相比，鳕鱼幼体与乔治浅滩顶部的潮汐混合水域的联系更为密切，并随着剩余环流被运送到乔治浅滩周围并向西南方向移动。 早春，其浮游动物猎物的丰度在热锋层层侧也更为丰富，幼虫往往与温跃层中最大猎物丰度的深度相关。 今年晚些时候，晚期幼体和早期幼体出现在河岸顶部，那里的浮游动物密度变得比侧面更大。 幼虫相对于混合和分层水域的垂直和区域分布的确切性质对于水平运输过程、温度对生长的影响以及浮游动物猎物的可用性可能非常重要。 该项目将采用新技术来检查鳕鱼幼虫的分布，并将与一项已资助的研究（NOAA）建立合作联系，该研究重点关注与整套浮游动物相关的春季分层过程的物理学，以及鳕鱼和黑线鳕幼虫的分布、生长和状况，从而形成了一个强大的跨学科项目。 ***