Collaborative Research: The impact of multiple nursery areas and adult age structure on the population dynamics of marine fishes

许多海洋种群表现出复杂的生活史，其中幼虫和幼年阶段在空间上与成虫分开。这是许多沿海产卵、依赖河口的鱼类的情况，它们利用多个河口作为育苗地，以确保任何一个河口的招募失败不会转化为种群水平的全部招募失败。对于这些物种来说，产卵的地点和时间被认为调节了向潜在的河口苗圃供应幼虫的模式。此外，许多这些物种表现出年龄依赖的沿海迁移，其幅度随着年龄的增长而增加。因此，种群年龄结构的变化有可能影响幼虫向苗圃的供应模式和招募模式的结构。研究人员将采用综合的经验和模拟方法来研究美国东海岸大西洋鲱鱼（Brevoortia tyrannus）河口苗圃的幼虫供应来源、模式和后果。第一个目标将是量化这些苗圃对整个海岸招聘的贡献。将对从马萨诸塞州到乔治亚州的幼鱼苗圃进行取样，并对其耳石的微化学成分进行表征。这些化学特征将被用来确定成年鲱鱼在整个海岸种群中的苗圃亲缘关系。调查人员将检验一个零假设，即切萨皮克湾仍然是人口中最重要的新兵来源。通过确定人口中不同年级的成年人的托儿所亲和力，他们将评估托儿所的贡献是否随时间而变化或转移。第二个目标是使用种群模型与基于个体的耦合物理-生物学招募模型相关联，以评估已知的成年鲱鱼的年龄依赖迁移是否足以引起观察到的鲱鱼幼虫分布的变化，这些幼虫在潜在的苗圃区域播种。模拟模型将有助于评估观察到的鲱鱼幼鱼分布变化背后的机制。这项工作将有助于对海洋种群空间结构调控的基本理解。过去十年来，一些依赖河口的海洋物种的活动范围扩大，其幼虫分散，而其他物种的长期补充减少。这个综合研究项目旨在探索人口统计学、海洋环流和苗圃多样性对随后的种群动态的影响。考虑到许多河口育苗区栖息地质量的变化，以及气候变化对海洋环流的预期影响，单个物种的分布变化可能会变得更加普遍。此外，鉴于许多依赖河口的物种在许多海洋生态系统中发挥的关键作用，了解分布变化将对它们所属生态系统的结构和功能产生直接影响。该项目还将在目前国家需要的研究领域（定量渔业生态学、物理海洋学）培训青年科学家。

Many marine populations exhibit complex life histories in which larval and juvenile stages are spatially separated from adults. This is the case for many coastal-spawning, estuarine-dependent fishes which utilize multiple estuaries as nursery grounds to ensure that recruitment failure in any single estuary does not translate to total recruitment failure at the population level. For these species, the location and timing of spawning is believed to regulate the pattern of supply of larvae to potential estuarine nursery areas. Furthermore, many of these species exhibit age-dependent coastal migrations which increase in amplitude with age. Thus, there is the potential that changes in the age structure in the population can affect the pattern of supply of larvae to nursery areas and structure the pattern of recruitment. The investigators will carry out an integrated empirical and simulation approach to study the sources, patterns and consequences of larval supply to estuarine nursery areas for Atlantic menhaden (Brevoortia tyrannus) along the East Coast of the US. The first goal will be to quantify the contribution of these nursery areas to coast wide recruitment. Juvenile menhaden from nursery areas from Massachusetts to Georgia will be sampled and the microchemical constituents of their otoliths will be characterized. These chemical signatures will be used to assign the nursery affinities of adult menhaden in the coastwide population. The investigators will test the null hypothesis that the Chesapeake Bay remains the most important source of recruits to the population. By determining the nursery affinities of adults from different year classes in the population they will assess whether the contribution of nurseries varies or has shifted over time. The second goal is use a population model linked to an individual-based coupled physical-biological model of recruitment to evaluate whether the known age-dependent migrations of adult menhaden are sufficient to cause the observed shifts in the distribution of larval menhaden that seed potential nursery areas. The simulation model will assist in evaluating mechanisms behind observed changes in the distribution of juvenile menhaden.This work will contribute to the fundamental understanding of the regulation of spatially-structured marine populations. The last decade has seen the range extension of several estuarine-dependent marine species with dispersive larvae and the long-term recruitment decline of others. This integrated research program seeks to explore the effects of population demography, oceanographic circulation, and nursery site diversity on subsequent population dynamics. Given the documented changes in habitat quality in many estuarine nursery areas, and the anticipated impacts of climate change on oceanographic circulation, distributional changes in individual species are likely to become more common. Moreover, given the pivotal role that many estuarine-dependent species play in many marine ecosystems, understanding distributional changes will have direct consequences for the structure and function of the ecosystems to which they belong. The project will also train young scientists in areas of research (quantitative fisheries ecology, physical oceanography) for which there is current a national need.