Recruitment of Marine Fish Larvae to Estuarine Nursery Systems: Insights from High Resolution Analysis of Otolith Chemistry and Hydrodynamics

海洋生态学的一个基本问题是生物和物理过程在海洋种群的丰富和持久性中所起的作用。虽然对底栖生物和潮间带生物有了一些了解，但这些因素在依赖河口的鱼类中的相对重要性尚待确定。在某种程度上，依赖河口的鱼类更难以研究，因为它们经历了个体发育栖息地的变化。在它们的早期生活中，它们被岸上的洋流运送到大陆架上，然后到达河口育儿区相对狭窄的入口。然后，幼虫必须通过河口进入河口，直到进入适合幼鱼生长和生存的中盐和寡盐生境。更复杂的是，许多这些经济价值鱼类固有的产卵季节的长度和产卵范围的地理宽度。对于依赖河口的鱼类，很难将重要性归于任何一个因素，部分原因是逻辑。例如，幼虫进入河口是典型的偶发事件。因此，科学家们只有在能够长期每天监测幼虫供应的情况下才能检查幼虫进入。即使如此，当产卵广泛分布时，幼虫来源不明。然而，仪器和技术的改进允许一种不同的方法，这对产卵期较长的鱼类在后勤上更可行。这些研究人员已经开发出量化编码在鱼耳石（耳骨）中的化学特征的技术，这种特征使我们能够确定幼鱼的产卵地点和时间。此外，调查人员还可以通过对新定居的幼鱼进行随机抽样和对其切片耳石进行化学分析来确定进入河口的日期和来源位置。这种方法提供了产卵源和进入河口的时间为少数年轻的鱼生存，并达到托儿所。通过结合这些数据在整个招聘季节，每天幼虫进入的时间序列也可以产生。当这些时间序列与每天测量的物理过程在河口，调查人员可以估计的时间和地点的相对重要性，随后通过河口和到达苗圃的理由产卵。这项研究的时机是特别合适的，因为这一建议的重要杠杆作用将提供一项研究，最近资助的物理海洋学计划在美国国家科学基金会。这项合作研究的目的是回答这个问题“如何的幅度和时间招聘到切萨皮克湾依赖于产卵源和近岸的物理过程？“研究的直接结果将是更好地了解河口近岸物理过程与幼虫供应和定居之间的联系。研究结果将指明识别产卵模式的方法，从而成功招募，从而确定包括当地种群的鱼类来源。最后，现代渔业管理方法越来越多地依赖于对补充的空间过程的了解，以确定和保护重要的鱼类栖息地，以保护不断减少的种群。这项研究将通过耳石化学追踪幼虫扩散路径，大大提高对本地和集合种群之间幼虫连接性的理解，并将为海洋种群和保护区的管理提供重要信息。

Jones9876565A fundamental question in ocean ecology is the role that biological and physical processes play in the abundance and persistence of marine populations. Although some understanding has been gained about benthic and intertidal organisms, the relative importance of these factors has yet to be determined in estuarine-dependent fishes. In part, estuarine-dependent fishes are more difficult to study because of the ontogenic habitat shifts that they experience. During their early lives they are transported across the continental shelf by onshore currents before arriving at the comparatively narrow entrances to estuary nursery areas. Larvae must then travel through the mouth and into the estuary until settling into meso and oligohaline habitats suitable for juvenile growth and survival. Further complicating the picture are the length of the spawning season and the geographic breadth of the spawning range inherent to many of these economically valuable fishes.For estuarine-dependent fishes, the difficulty in attributing importance to any one factor has, in part, been logistic. For instance, larval entry into estuaries is typically episodic. Consequently, scientists have only been able to examine larval entry when it was possible to monitor larval supply daily over long periods. Even so, larval source was unknown when spawning was broadly distributed. However, improvement in instruments and techniques permit a different approach that is logistically more feasible for fish with broad spawning periods. These investigators have developed techniques to quantify chemical signatures encoded in the fish's otolith (earbone), a signature that allows us to determine a young fish's spawning location and time. Moreover, the investigators can determine date of entry into the estuary and source location by randomly sampling newly-settledjuveniles and chemically analyzing their sectioned otoliths. This approach provides the spawning source and timing of ingress to the estuary for the few young fish that survive and reach the nursery grounds. By combining these data throughout the recruitment season, a time series of daily larval ingress can also be generated. When these time series are correlated with daily measurements of the physical processes at an estuary mouth, the investigators can estimate the relative importance of the time and place of spawning on subsequent passage through the estuary and arrival at the nursery grounds. The timing of this study is particularly opportune, as significant leverage for this proposal will be provided by a study recently funded by the Physical Oceanography program within National Science Foundation.This collaborative research is designed to answer the question "How is the magnitude and timing of recruitment to Chesapeake Bay dependent on spawning source and nearshore physical processes?" An immediate result of the research will be a better understanding of the linkage between nearshore physical processes at an estuary mouth to larval supply and settlement. The results will point the way to identifying pattems of spawning that result in successful recruitment and therefore the sources of fish that comprise local populations. Finally, modern approaches to fisheries management increasingly rely on knowledge of spatial processes on recruitment for defining and preserving essential fish habitat to protect declining populations. This study will significantly enhance the understanding of larval connectivity among local and metapopulations by tracking larval dispersal paths via otolith chemistry and will provide critical information for the management of marine populations and reserves.