Complex Predator-Prey Interactions in Marine Soft-Bottom Communities: Crabs, Clams, and Patch Dynamics

本研究的总体目标是定量地确定海洋软底生物群落中捕食者-猎物动态的相互作用调控因素和潜在机制。研究人员有广泛的背景知识和创新的超声波生物遥测技术来检查切萨皮克湾一个小河口（罗德河）的捕食者-猎物复杂。研究人员将测量导致功能性和聚集性反应变化的捕食者行为的组成部分。捕食者-猎物复合体包括大型蓝蟹（Callinectes sapidus），它们以两种常见的水生蛤蜊（Macoma balthica和Mya arenaria）为食，也以小型蓝蟹为食。底栖鱼类也是大量的捕食者，它们以蛤蚌虹吸和其他生活在沉积物中的底栖无脊椎动物为食，但不以整个大蛤为食。早期的研究主要集中在猎物种类、沉积物类型和猎物密度对猎物遭遇强捕食的持久性的交互影响，重点是蓝蟹觅食蛤的功能反应。生物遥测已被用于确定捕食者行为变化的尺度和关键猎物斑块之间的运动。因此，这些研究集中在蓝蟹对猎物斑块的聚集反应上，并将这种捕食者-猎物系统的调节因素、潜在机制和最终动态联系起来。本研究将：1)确定调节主要捕食者（大蓝蟹）聚集反应的交互因子（猎物种类、猎物密度和捕食者密度）；2)确定了调节两种交替猎物（蛤和小蟹）捕食率的相互作用因子（猎物密度和分布、栖息地避难所和捕食者密度）；3)研究大蓝蟹在捕食斑块中聚集和在小蟹和蛤之间转换的行为/生理机制。

The overall goal of this research is to determine quantitatively, the interactive regulatory factors and underlying mechanisms of predator-prey dynamics in a marine soft-bottom community. The researchers have extensive background knowledge as well as an innovative ultrasonic biotelemetry techniques to examine the predator-prey complex in a small sub-estuary (the Rhode River) of Chesapeake Bay. The researchers will measure the components of predator behavior which lead to changes in the functional and aggregative responses. The predator-prey complex includes large blue crabs (Callinectes sapidus) which feed on two common species of infaunal clams (Macoma balthica and Mya arenaria) as well as cannibalizing small blue crabs. Demersal fish are also abundant predators which feed extensively on clam siphons and other benthic invertebrates which live in the sediments, but not on large whole clams. Earlier work focused on the interactive effects of prey species, sediment type, and prey density on the persistence of prey encountering intense predation, with emphasis on the functional response of blue crabs foraging on clams. Biotelemetry has been used to determine the scales of variation in predator behavior and movement between key prey patches. Thus, these investigatins focus on the blue crab's aggregative response with prey patches, which links the regulatory factors, underlying mechanisms, and resulting dynamics of this predator-prey system. This research will: 1) determine the interactive factors (prey species, prey density, and predator density) regulating the aggregative response of the main predator (large blue crabs); 2) determine the interactive factors (density and distribution of prey, habitat refugia, and predator density) regulating predation rates upon two alternate prey (clams and small crabs); and 3) investigate the behavioral/physiological mechanisms of large blue crabs aggregating in prey patches and switching between small crabs and clams.