Collaborative Research: Cobble landscape structure, spatial gradients in predation, and variable demographic bottlenecks in the American lobster

了解定居前和定居后过程如何相互作用以控制海洋开放种群的动态仍然是海洋生态学的核心问题。本研究以美洲大龙虾为模型系统，研究了苗圃栖息地结构如何影响定居后的死亡和扩散。该研究的中心主题是发现鹅卵石景观结构（即斑块）和新英格兰海岸线上龙虾种群密度、捕食者丰度和捕食者多样性的梯度是否相互作用，导致假设的幼年龙虾人口瓶颈强度的区域差异。当小龙虾到达生长阶段时，它们必须在鹅卵石庇护所外觅食，即使它们还没有达到躲避捕食者（例如底栖鱼）的大小避难所，它们也可能成为有限的避难所。潜在的假设是，鹅卵石斑块和庇护所的限制将导致人口瓶颈，限制龙虾在捕食者密度高的地区（如新英格兰南部）的丰度，而在捕食者密度低的地区（如缅因州）则不会。十多年来，国家支持的新英格兰海岸幼虫后沉降调查，以及noaa支持的侧扫描声纳、远程车辆和潜水调查，以鹅卵石栖息地结构和沉降强度为指标，评估龙虾丰度与栖息地利用之间的区域联系。这项由美国国家科学基金会资助的研究将通过操纵实验来补充调查。这些研究的目的是确定在以下方面是否存在区域差异：(1)龙虾在栖息地斑块之间的运动；(2)被捕食风险；(3)局部遮蔽限制；4)住所忠诚度（换住所的倾向）。在四个地区（罗德岛州、马萨诸塞州、中部海岸和缅因州东部）的两个地点中，研究人员将构建由一个破碎的和一个非破碎的鹅卵石斑块阵列组成的实验景观。在这些景观中，幼虾从它们被释放的源斑块迁移到周围目的地斑块的比例将与阵列类型、捕食者丰度、捕食风险和龙虾种群密度相关，以推断定居斑块中龙虾损失的分散和死亡率的相对贡献。在另一个单独的实验中，将部署人工庇护所的尺寸阵列，以量化区域特定尺寸庇护所限制的程度。将进行相应的捕食实验，以确定对捕食脆弱性的区域差异。龙虾的大小既受到当地庇护所的限制，又容易被捕食，这将表明幼虾的大小受到人口瓶颈的影响。最后，他们将对龙虾进行标记，以测量庇护所的保真度，以确定庇护所之间的移动与龙虾密度、捕食者指数或栖息地之间的斑块之间的关系。这些综合项目的成果将广泛传播。美国龙虾是新英格兰地区经济上最重要的单一物种渔业。通过解决龙虾定居后过程的黑箱问题，这些科学家将为长期以来的科学愿景做出贡献，即开发一个大规模的空间明确模型，将远洋和底栖生物过程结合起来，预测空间和时间上的收成。其结果将有助于资源管理者和渔业继续开发渔业预测工具。学生培训也是这项工作不可或缺的一部分：拟议的研究将成为SDSU研究生毕业论文的基础，每年至少有四名本科生将作为实习生获得学分。该项目的另一个重要的教育组成部分是继续开发名为“从孵化到捕获”的交互式光盘和基于网络的活动，该活动已被美国国家科学教师协会认可为K-12学习的有用教育工具（见www.scilinks.org）。

Understanding how pre- and post-settlement processes interact to govern the dynamics of marine open populations remains a central issue in marine ecology. In this study the American lobster Homarus americanus is used as a model system to determine how nursery habitat structure influences post-settlement mortality and dispersal. The central theme of the study is to find if cobble landscape structure (i.e., patchiness) and gradients in lobster population density, predator abundance and predator diversity along the New England coastline interact to cause regional variation in the strength of a hypothesized juvenile lobster demographic bottleneck. As juvenile lobsters reach the emergent phase they must forage outside of cobble shelter and may become shelter limited even though they have not reached a size refuge from predators (e.g., groundfish). The underlying hypothesis is that cobble patchiness and shelter limitation will cause a demographic bottleneck that limits lobster abundance in regions of high predator density (e.g., southern New England) but not in regions of low predator density (e.g., Maine). Supplementing more than a decade of state-supported postlarval settlement surveys along the New England coast, and NOAA-supported sidescan sonar, remote vehicle and scuba surveys to evaluate the regional linkage between lobster abundance and habitat use with indices of cobble habitat structure and settlement strength this NSF-sponsored research will complement the surveys with manipulative experiments. These are aimed at determining if regional differences exist in: (1) lobster movements among habitat patches; (2) predation risk; (3) local shelter limitation; and 4) shelter fidelity (propensity to switch shelters). In each of two sites in four regions (Rhode Island, Massachusetts, mid-coast and eastern Maine) the investigators will construct experimental landscapes consisting of one fragmented and one non-fragmented cobble patch array. The proportion of juvenile lobsters moving from a source patch where they are released to surrounding destination patches within these landscapes will be correlated with array type, predator abundance, predation risk, and lobster population density to infer the relative contributions of dispersal and mortality in lobster losses from settlement patches. In a separate experiment, size arrays of artificial shelters will be deployed to quantify the degree of size-specific shelter limitation by region. Corresponding predation experiments will be conducted to determine how vulnerability to predation varies regionally. The lobster size that is both locally shelter-limited and still vulnerable to predation will indicate the size at which juveniles are subject to a demographic bottleneck. Finally, they will tag lobsters to measure shelter fidelity to determine how movements between shelters correlates with lobster density, predator indices, or habitat patchiness among sites. Results of these integrated projects will be broadly disseminated. The American lobster is the most economically important single-species fishery in New England. By addressing the black box of lobster post-settlement processes, these scientists will contribute to a long-standing scientific vision of developing a large-scale spatially explicit model that couples pelagic and benthic processes to predict harvests in space and time. Their results will aid resource managers and the fishing industry in the continued development of predictive tools for the fishery. Student training is also integral to this work: the proposed research will form the basis for a thesis or dissertation for an SDSU graduate student, and at least four undergraduates per year will serve as interns earning academic credit. Another important educational component of this project is the continued development of an interactive CD and web-based activity called Hatch-to-Catch already recognized by the National Science Teachers Association as a useful educational tool for K-12 learning (see www.scilinks.org).