Collaborative Research: US GLOBEC: Predation Impacts on Target Specie: Roles of Frontal Proceses and Small Predator Species

[9806465] georgesbank项目旨在了解四种目标物种（鳕鱼和黑线鳕的幼虫，以及它们的主要饲料猎物桡足类Calanusfinmarchicus和pseudoalanus spp）种群动态的物理和生物过程。这些过程的核心是无脊椎动物和鱼类捕食者对这四种物种的捕食，本研究的目的是描述和量化这一死亡来源。该方法结合了乔治河岸上捕食者和目标猎物物种的丰度和共存信息，这些信息来自于持续的大规模调查，以及主要捕食者物种的捕食特异性和捕食率的新数据。在第一阶段和第二阶段，博士。Madin， Sullivan和Bollens使用了肠道内容物分析（通过显微镜和免疫分析）和喂养实验（在船上和实验室，在小容器和mesocosms中）来获得喂养数据。前两个阶段的实地抽样集中于分层效应（1995年）和水和生物的来源、保留和损失（1997年）的主题。在第三阶段，他们将指导实地工作（1999年）解决有关额叶区对目标物种及其捕食者的运输、聚集和相互作用的影响的问题。传统的采样将辅以视频系统来检测大型胶状捕食者。对浮游生物群落动态研究的重要新贡献将是确定杂食性桡足类动物在限制食草动物生产中的作用，以及湍流在控制胶状捕食者捕食率中的作用的实验研究。乔治滩的自然和水文环境为目标物种和它们的捕食者之间的生物相互作用奠定了基础。河岸的水深和它周围的环流模式在其南北边界和60米等深线上形成了锋面区域，在混合良好的中央波峰和季节性分层的南翼之间。最后一个区域，潮汐混合锋，将两个在水文和生物方面非常不同的区域分开。这些研究人员将在1999年的两次巡航中在这一前沿工作，以确定沿锋面和整个锋面的猎物和捕食者的分布和丰度，锋面动态对聚集和相互作用的影响，以及生物从一侧到另一侧的交换。Crest和侧翼地区是他们在以前的过程研究中集中精力的地方，目标物种和它们的主要捕食者之间的发生似乎有一个关键的重叠。与锋面相关的湍流、收敛和交换可能对不同捕食生物的捕食者产生不同的影响。长期了解乔治滩系统的关键是建立全面的物理-生物模型。本研究将为这些模型提供与季节、地点、物种、主要捕食者、阶段和猎物密度有关的捕食死亡率数据。

9806465MadinThe GLOBEC Georges Bank program is seeking to understand the physical and biological processes which determine the population dynamics of four target species -- larval cod and haddock, and their main forage prey, the copepods Calanusfinmarchicus and Pseudocalanus spp. Central among these processes is predation by invertebrate and fish predators on these four species, and the objective of this study is the description and quantification of this source of mortality.The approach combines information on the abundance and co-occurrence of predators and target prey species on Georges Bank, derived from the continuing Broad Scale Survey, with new data on feeding specificity and rates of the principal predator species. During Phases I and II, Drs. Madin, Sullivan and Bollens have used both gut-contents analysis (by microscopy and with immuno-assays) and feeding experiments (shipboard and laboratory, in small containers and mesocosms) to obtain feeding data. The field sampling during the first two Phases focused on the themes of stratification effects (1995) and source, retention and loss of water and organisms (1997). In Phase III they will direct field efforts (in 1999) to questions concerning effects of frontal regions on the transport, aggregation and interaction of target species and their predators. Conventional sampling will be supplemented with a video system to detect large gelatinous predators. Significant new contributions to the study of plankton community dynamics will be identification of the role of omnivorous copepods in limiting production of herbivores, and experimental studies of the role of turbulence in controlling predation rates of gelatinous predators.The physical and hydrographic environment of Georges Bank sets the stage for the biological interplay of target species and their predators. The bathymetry of the Bank and the pattern of circulation on and around it create frontal regions on its north and south boundaries, and along its 60 m isobath, between the well-mixed central Crest and the seasonally stratified southern Flank. This last region, the tidal mixing front, divides two areas which are very different in terms of hydrography and biology. These researchers will work at this front on two cruises in 1999, to determine the distribution and abundance of prey and predators along and across the front, the effect of frontal dynamics on aggregation and interaction, and the exchange of organisms from one side to the other. The Crest and Flank regions are where they have concentrated efforts in previous process studies, and where there appears to be a critical overlap in occurrence between target species and their main predators. Turbulence, convergence and exchange associated with the front may have different effects on predators with different feeding biologies. The key to long-term understanding of the Georges Bank system is development of comprehensive physical-biological models. This study should make a major contribution to these models with data on predation mortality which is specific to season, location, species, and for principal predators, stage and density of the prey.