Telemetric and Genetic Analyses of Habitat Use, Philopatry and Natal Homing of a Coastal Shark Species in Continental Nursery Areas

海洋中的迁徙脊椎动物，包括海鱼、海龟、海鸟和海洋哺乳动物，以一种尚未完全了解的方式与海洋边缘联系在一起。在其生活史的关键阶段，这些海洋动物往往依靠近岸地区进行繁殖、摄食和其他基本活动。将一个沿海地区与另一个沿海地区区分为这些迁徙物种的首选栖息地的情况鲜为人知，特别是在广袤的大陆地区，那里的适宜栖息地似乎很普遍。一个物种如何以及为什么选择一个特定的大陆沿海地区进行繁殖和早期生命阶段--以及同一地理位置是否以进化上固定的方式被个别动物利用--在某种程度上仍然是一个谜，特别是在鲨鱼的情况下，鲨鱼是海洋中占主导地位的顶端捕食者。Mote海洋实验室自1991年以来对鲨鱼育婴区进行的先前研究表明，至少有14种沿海鲨鱼利用佛罗里达州墨西哥湾沿岸的近岸地区作为幼崽和/或育婴区。这项研究表明，从5月到9月，新生的黑鳍鲨(Carcharhinus Limbatus)在佛罗里达州海湾沿岸的海岸海湾和河口大量存在，然后向南迁徙过冬。该项目将研究海湾作为新生和幼年斑鲨的托儿所的使用，试图确定该区域在幼鲨生活史中的生态作用，以及这些区域的使用是否导致了亲缘关系的进化。研究的目标是：1)描述幼年斑鲨在育儿区的活动模式、栖息地范围和栖息地偏好，并确定这些动物在特定大陆育婴区停留的时间；2)估计一岁大的动物返回育儿区的比率(繁殖)，并确定它们是否继续使用育婴区；3)通过对种群内遗传变异的分析，确定成年雌性鲨鱼是否返回其出生的育婴区产卵(幼鲨归巢)。这项研究将在Terra Ceia Bay进行，Terra Ceia Bay是佛罗里达州墨西哥湾中部沿岸的一个大陆苗圃区域。在春季、夏季和秋季，将在苗圃区域内部署最先进的远程声学水听器系统，以持续监测装有超声波发射器的鲨鱼的位置和运动。从水听器站收集的数据将被用来确定幼鲨在育婴区的停留时间、活动模式、栖息地范围和栖息地用途。一旦确定使用Terra Ceia Bay作为新生斑鲨的保育区，就必须审查特定的保育区是否继续是幼鲨生活史中不可或缺的一部分。将使用水听器系统并通过在邻近的三个沿海苗圃地区(松岛海湾、扬基敦、万岛)进行采样，来检查幼鲨返回其出生苗圃的比率。对Terra Ceia Bay的持续监测将提供与非新生青少年相同的个体的停留时间、活动模式、栖息地范围和栖息地用途的信息。远程声学系统的使用将为实现本研究的前两个目标提供主要数据。遗传分析将测试是否发生亲水现象，以支持水听器的结果，并测试成年雌性的产后归巢。这些分析将为评估雌性鲨鱼产后归巢的假说提供必要的数据。虽然在其他动物物种中，亲水性和出生归宿是广为人知的，但这项研究将首次有针对性地在板足动物种群中阐明这些行为，特别是居住在大陆地区的动物，那里合适的托儿所栖息地广泛且不是孤立的。这项研究的结果将提供关于幼鲨习性的连续数据，在追踪过程中不会受到科学家的干扰。总体而言，该项目将研究沿海育苗区在生活在大陆架水域的鲨鱼物种生活史中的更大作用。

The ocean's migratory vertebrates, including marine fishes, sea turtles, sea birds and marine mammals, are tied to the sea's margins in ways that are not completely understood. These marine animals often depend on inshore regions for reproduction, feeding and other essential activities during critical stages of their life histories. What delineates one coastal area from another as preferred habitat for these migratory species is poorly known, particularly for broad continental regions where suitable habitat appears to be widespread. How and why a species selects a specific continental coastal area for reproduction and early life stages -and whether the same geographic site is utilized by individual animals in an evolutionarily fixed way- remain somewhat of a mystery, particularly in the case of sharks, the predominant apex predators in the sea. Previous research on shark nursery areas conducted by Mote Marine Laboratory since 1991 has shown that at least 14 coastal shark species utilize inshore regions of the Gulf of Mexico coast of Florida as pupping and/or nursery areas. This research has shown that neonate blacktip sharks (Carcharhinus limbatus) are abundant in coastal bays and estuaries of the Florida Gulf coast from May through September before migrating south for the winter. This project will examine the use of a bay as a nursery area for neonate and juvenile C limbatus, attempt to define the ecological role of this area in the life history of young sharks and if use of these areas has resulted in evolution of philopatry. The research objectives are to: 1) delineate the activity patterns, home range and habitat preferences of young C limbatus in a nursery area and ascertain how long these animals reside within a specific continental nursery area; 2) estimate the return rate (philopatry) of one year-old animals to the natal nursery and defiiie their continued use of the nursery area; and 3) determine if adult female sharks return fo their natal nursery area to give birth (natal homing) through analysis of genetic variation within the population. This research will be conducted in Terra Ceia Bay, a continental nursery area along the central Gulf coast of Florida. A state-of-the-art system of remote acoustic hydrophones will be deployed within the nursery area during spring, summer and fall months to continuously monitor the location and movement of sharks fitted with ultrasonic transmitters. Data collected from hydrophone stations will be used to determine the residence time, activity patterns, home range and habitat use of young sharks in the nursery area. Once the use of Terra Ceia Bay as a nursery area for neonate C. limbatus has been defined it will be important to examine whether specific nursery areas continue to be integral in the life history of juvenile sharks. The return rate of young sharks to their natal nursery will be examined using the hydrophone system and by conducting sampling in three adjacent coastal nursery areas (Pine Island Sound, Yankeetown, Ten Thousand Islands). Continued monitoring of Terra Ceia Bay will provide information on residence time, activity patterns, home range and habitat use for the same individuals as non-neonate juveniles. Use of the remote acoustic system will provide the primary data to accomplish the first two objectives of this study. Genetic analyses will test for the occurrence of philopatry to support hydrophone results and test for natal homing by adult females. These analyses will provide the data necessary to evaluate the hypothesis of natal homing by female sharks. Although philopatry and natal homing are widely known in other animal species, this study will provide the first directed effort to elucidate these behaviors within an elasmobranch population, particularly one inhabiting a continental region where suitable nursery habitat is widespread and not insular. Results of this study will present continuous data concerning the habits of young sharks without disturbance by scientists during tracking. Overall, this project will examine the larger role of the coastal nursery area in the life history of shark species inhabiting continental shelf waters.