Source, Trophic Opportunities and Fate of Billfish Larvae in the Diverse Pelagic Habitats of the Straits of Florida

长嘴鱼是一种大型中上层鱼类，生活在世界海洋的热带和亚热带沃茨。它们是中上层食物网中的顶级捕食者，同时也是咸水垂钓者最受欢迎的鱼类。这些海洋“巨人”支撑着数百万美元的体育捕鱼业，并构成了金枪鱼延绳钓努力的重要副渔获物。不幸的是，人类活动导致长嘴鱼种群的显著下降;蓝马林被认为是在最大可持续产量维持捕捞所需的40%以下。尽管它们的生态状况危急，但关于这些生物的现有生物信息极为有限。专注于长嘴鱼的早期生活史阶段是获得有价值的生物学数据的一种易处理的手段。例如，收集早期幼虫阶段的数据，结合关于环流的数据，可作为确定何时何地产卵的手段。调查的中上层生境变量与发生的长嘴鱼幼虫可能提供洞察产卵和早期生存所需的环境条件。即使在其早期生活史中，长嘴鱼也可能是中上层食物链的重要组成部分，特别是作为浮游动物和仔鱼的捕食者。 本研究的总体目标是一个季节性解决的理解的年度周期的长嘴鱼产卵，幼虫生长，喂养，运输内的复杂环境的佛罗里达海峡。作为顶级掠食者，长嘴鱼在中上层食物网中发挥着关键但尚未确定的作用。在这里，我们研究的早期生活史的长咀鱼在海洋学背景下的佛罗里达海峡（SSF）。SSF是一个离散的、相互作用的水团和远洋环境的复杂系统。初步数据表明，长嘴鱼幼虫发生在三个不同的补丁整个SSF可预见的。该项目的目的是：1）确定SSF内三个不同的长嘴鱼幼虫斑块的来源; 2）确定这些斑块在长嘴鱼幼虫的营养和生长环境方面的差异; 3）调查来自这些不同斑块的长嘴鱼幼虫的运输命运。实地工作分为三个独立的研究部分：第一项研究将解决两岸特征的时间质量（即，水团分布、长嘴鱼幼体斑块和浮游动物群落结构）。每月采样（包括鱼类浮游生物和浮游动物拖，CTD，荧光，ADCP测量）超过两年将通过耳石老化研究和循环模式的产卵地点的估计。关于幼虫生长率的进一步耳石研究将与关于浮游动物群落组成和动态的研究相结合，以确定斑块之间的营养动力学差异。第二项研究将扩大我们努力的空间尺度，以研究与幼长嘴鱼斑块的形成、维持和命运有关的沿海峡动态。第二年将进行一次航行，将包括上述同一套测量以及ARGOS跟踪的漂流物测量。第三年的第三项研究将采用拉格朗日技术，通过佛罗里达海峡系统跟踪来自假设产卵地点的长嘴鱼幼虫，将这些轨迹与观察到的海峡两岸空间斑块和离散斑块的最终命运联系起来。取样将包括在与一组漂流物轨道垂直的站点进行的一组类似的测量。 拟议研究的结果将提供关键的新信息，这些重要的中上层捕食者的早期生活史和生态，以及不同的水团和中上层食物网的营养动力学之间的相互作用。对特定叶绿素形成、维持和归宿的进一步认识。a/浮游动物/幼鱼斑块也将有助于深入了解上升流的作用以及锋面边界和浅岸之间的水团交换。

Billfishes are a complex of large pelagic fishes that occur in the tropical and subtropical waters of the world's oceans. They are top predators in the pelagic food web and, simultaneously, the most sought-after fishes for saltwater anglers. These oceanic "giants" support a multi-million dollar sportfishing industry and comprise a significant bycatch of tuna longline efforts. Unfortunately, human activities have led to significant declines in billfish stocks; blue marlin are thought to be at less than 40% of that necessary to sustain fishing at maximum sustainable yields. Despite their critical ecological status, the biological information available on these organisms is extremely limited. Focusing on the early life history stages of billfishes is a tractable means of obtaining valuable biological data. For example, collection of early larval stages can be used, in conjunction with data on circulation, as a means of determining when and where spawning occurs. Investigation of the pelagic habitat variables associated with the occurrence of billfish larvae may provide insight into environmental conditions required for spawning and early survival. Even in their early life history, billfishes are likely important constituents of the pelagic food chain, especially as predators on zooplankton and larval fishes. The overall objective of this study is a seasonally resolved understanding of the annual cycle of billfish spawning, larval growth, feeding, and transport within the complex environment of the Straits of Florida. As top predators, billfishes play a critical yet undefined role in the pelagic food web. Here we examine the early life history of billfishes within the oceanographic context of the Straits of Florida (SSF). The SSF is a complex system of discrete, interacting water masses and pelagic environments. Preliminary data suggest that billfish larvae occur predictably in three distinct patches across the SSF. The project is designed to 1) identify the sources of the three distinct larval billfish patches within the SSF; 2) determine how the these patches differ in terms of the trophic and growth environment of the billfish larvae; and 3) investigate the transport fates of larval billfishes from these different patches. The fieldwork is divided into three separate study components: The first study will address the temporal qualities of cross-Strait features (i.e., water mass distribution, larval billfish patches, and zooplankton community structure). Monthly sampling (consisting of ichthyoplankton and zooplankton tows, CTD, fluorometry, and ADCP measurements) over two years will be linked via otolith aging studies and circulation patterns to estimates of spawning locations. Further otolith work on larval growth rates will be coupled to zooplankton work on community composition and dynamics to identify trophodynamic differences among patches. The second study will expand the spatial scale of our efforts to examine the along-Strait dynamics relating to the formation, maintenance, and fate of larval billfish patches. A single cruise will be made during the second year and will include the same suite of measurements as above as well as ARGOS-tracked drifter measurements. The third study during year 3 will incorporate Lagrangian techniques to track larval billfishes from hypothesized spawning sites through the Straits of Florida system to link these trajectories to the observed cross-Strait spatial patchiness and ultimate fate of the discrete patches. Sampling will consist of a similar set of measurements conducted at stations normal to the track of a group of drifters. Results of the proposed study will provide critical new information regarding the early life history and ecology of these important pelagic predators as well as the interaction between different water masses and the trophodynamics of pelagic food webs. A further understanding of the formation, maintenance and fate of particular chl. a/zooplankton/larval fish patches also will provide insights into understanding the role of upwelling and water mass exchange across frontal boundaries and shallow banks.