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的过程如何相互作用，以管理海洋开放种群的动态仍然是海洋生态学的一个中心问题。 在这项研究中，美国龙虾Homarus americanus被用来作为一个模型系统，以确定苗圃栖息地结构如何影响定居后的死亡率和扩散。 研究的中心主题是寻找鹅卵石景观结构（即，斑块）和梯度的龙虾种群密度，捕食者丰富度和捕食者多样性沿着新英格兰海岸线相互作用，导致区域变化的强度的一个假设的少年龙虾人口瓶颈。 当幼年龙虾到达紧急阶段时，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的大小庇护所，也可能成为庇护所有限的动物（例如，底栖鱼）。潜在的假设是，鹅卵石斑块和住房限制将导致人口瓶颈，限制龙虾在高捕食者密度地区的丰度（例如，新英格兰南部），但不是在低捕食者密度的区域（例如，缅因州）。 补充十多年的国家支持的新英格兰海岸沿着幼体定居点调查，和NOAA支持的侧扫声纳，远程车辆和水肺调查，以评估龙虾丰度和栖息地利用之间的区域联系与鹅卵石栖息地结构和定居强度的指数，这NSF赞助的研究将补充调查与操纵实验。 这些旨在确定是否存在区域差异：（1）栖息地斑块之间的龙虾运动;（2）捕食风险;（3）当地住房限制;和4）住房忠诚度（倾向于转换住房）。 在四个地区（罗得岛、马萨诸塞州、中部海岸和缅因州东部）的两个地点，研究人员将构建由一个碎片和一个非碎片鹅卵石斑块阵列组成的实验景观。 幼年龙虾从源补丁，他们被释放到周围的目的地补丁在这些景观的比例将与阵列类型，捕食者丰度，捕食风险，和龙虾种群密度推断的相对贡献的分散和死亡率在龙虾的损失结算补丁。 在另一项实验中，将部署人工避难所的大小阵列，以量化各地区特定大小避难所的限制程度。 相应的捕食实验将进行，以确定如何脆弱性捕食不同的区域。 龙虾的大小，这是当地的住房有限，仍然容易被捕食将表明在青少年受到人口瓶颈的大小。 最后，他们将标记龙虾来测量庇护所的保真度，以确定庇护所之间的运动如何与龙虾密度，捕食者指数或栖息地之间的斑块相关。 这些综合项目的成果将广泛传播。 美洲龙虾是新英格兰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匣子问题，这些科学家将有助于实现一个长期的科学愿景，即开发一个大规模的空间明确模型，将远洋和海底过程结合起来，以预测空间和时间上的收获。 他们的研究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：拟议的研究将形成SDSU研究生论文或论文的基础，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教育组成部分是继续开发一种名为“Hatch-to-Catch”的互动光盘和网络活动，该活动已被全国科学教师协会确认为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).