Retrospective Analysis of Dispersive and Retentive Behaviors of Young-of-the-Year Estuarine Fishes: Are Fish Otoliths Environmental Chronometers?

近年来，耳石微化学研究的进展为研究人员提供了一个强有力的手段来跟踪鱼类在个体发育过程中的扩散。该方法提供了空间和时间信息的鱼类扩散和运动。虽然利用耳石微化学重建海洋鱼类的环境历史是公认的和报道，根本的问题，鱼耳石是否可以作为“忠实的环境计时器？”基本上还没有经过测试。本计画验证耳石锶能反映河口及海洋鱼类个体发育早期盐度变化之假设。该假设将在切萨皮克湾进行评估，因为该系统包含环境梯度的极端范围。这项研究将严格检验耳石锶在实验室和野外环境中反映盐度的假设。研究方法分为三个层次：（1）对在恒定和波动的盐度和温度条件下饲养的个体进行回顾性的耳石锶元素分析;（2）对野外捕获和笼养个体进行耳石锶元素分析，并将耳石锶与环境盐度的关系作为现场验证的手段;（3）测量了切萨皮克湾一年生（YOY）河口鱼类扩散的宽尺度（如河口进出）和细尺度（河口运动）模式。空间行为将测量五个生态上重要的河口物种与对比的早期生活策略：美国鳗鱼Anguilla rostrata，美国沙鱼，白色鲈鱼Morone americana，现场Leiostomus xanthurus，和hogchoker Trinectes maculatus。Sr：Ca比值的准确度和精确度的物种特定估计将被用来评估耳石锶是否可以测量扩散沿着盐度梯度和追溯空间历史的YOY鱼类。

Recent advances in otolith microchemistry have provided researchers with a powerful means of tracking fish dispersal throughout ontogeny. The approach provides both spatial and temporal information on fish dispersal and movement. While the use of otolith microchemistry for reconstructing environmental histories of marine fishes is well recognized and reported, the fundamental question, whether fish otoliths can function as `faithful environmental chronometers?` remains largely untested. This project tests the hypothesis that otolith strontium is reflective of changing salinities during the early ontogeny of estuarine and marine fishes. The hypothesis will be evaluated in the Chesapeake Bay because this system contains extreme ranges in environmental gradients. The research will rigorously test the hypothesis that otolith strontium is reflective of salinity in both laboratory and field environments. The approach will be three-tiered, including: 1) retrospective elemental assays of otolith strontium of individuals reared under constant and fluctuating schedules of salinity and temperature levels; 2) elemental assays of otolith strontium of wild caught and caged individuals, and the relation otolith strontium to ambient salinity as a means of field verification; and 3) measurement of broad scale (e.g. estuarine ingress and egress) and fine scale (within estuary movements) patterns of dispersal by young of the year (YOY) estuarine fishes in the Chesapeake Bay. Spatial behaviors will be measured for five ecologically important estuarine species with contrasting early life tactics: American eel Anguilla rostrata, American shad Alosa sapidissima, white perch Morone americana, spot Leiostomus xanthurus, and hogchoker Trinectes maculatus. S pecies specific estimates of accuracy and precision of the Sr:Ca ratio will be used to evaluate whether otolith strontium can measure dispersal along a salinity gradient and hindcast spatial histories of YOY fishes.