Retrospective Determination of Atlantic Croacker Migration Through Laser-Based Elemental Analysis of Otoliths

在第一年存活下来的鱼的数量每年的变化（称为招募或年类强度）往往足以控制几年后渔业的成败。尽管在鱼达到可销售的尺寸之前就能估计出一年的班级实力会带来科学和经济效益，但事实证明，预测招生是一个难以实现的目标。造成大西洋黄花鱼年类强度逐年变化的可能机制包括产卵地点和时间的变化、随后平流到河口苗圃区的年龄和日期的变化、在河口的持续时间和相对生长速度，以及成年河口迁移的年龄和日期。结合基于耳石日生长环的年龄结构生长和存活测量，该项目将使用一种新的基于激光的元素分析技术（LS-ICPMS）来验证这些假设，以追溯确定孵化地点，并估计个体鱼随后迁徙的年龄和日期。这项技术是基于鱼耳石（耳石）的脱细胞特性，它是通过每天在中心核周围同心增加矿化组织而形成的。鉴于给定日环的元素组成反映了当天通过鱼鳃的水的元素组成，在某个年龄和/或日期的水团之间的迁移将被记录为耳石元素组成在适当的日增量上的变化。由此推论，孵化时间和孵化地点的水质量差异将反映在耳石核元素组成差异上。目前几乎没有（如果有的话）海洋鱼类种群的标记，更不用说过去的运动和水体关联的指标了。该项目的成功完成不仅对大西洋青花鱼的捕捞预测，而且对世界各地的捕捞、种群结构、迁徙和渔业管理的研究具有重要意义。

Year to year variations in the number of fish which survive the first year of life (termed recruitment or year class strength) are often sufficient to control the success or failure of the fishery a few years later. Despite the scientific and economic benefits which would result if year class strength could be estimated before fish reached a marketable size, recruitment prediction has proved to be an elusive goal. Likely mechanisms contributing to year-to-year variations in the year class strength of Atlantic croaker include variations in the location and timing of spawning, the age and date of subsequent advection to the estuarine nursery area, the duration and relative growth rate while in the estuary, and the age and date of migration of the estuary as an adult. In conjunction with age-structured measures of growth and survival based on otolith daily growth rings, this project will test these hypotheses using a new laser- based elemental analysis technique (LS-ICPMS) to retroactively determine the hatching site and estimate the age and date of subsequent migrations in individual fish. The technique is based on the acellular nature of the fish otolith (earstone), which forms through the concentric daily additions of mineralized tissue around a central nucleus. Given the fact that the elemental composition of a given daily ring reflects the elemental composition of the water which passed through the fish's gills on that same day, migration between water masses at some age and/or date will be recorded as a change in the elemental composition of the otolith at the appropriate daily increment. By corollary, water mass differences at the time and place of hatching will be reflected in elemental composition differences in the otolith nucleus. At present there are few (if any) markers of marine fish populations, let alone indicators of past movement and water mass association. Successful completion of this project has implications not only for recruitment predication of Atlantic croaker, but for studies of recruitment, stock structure, migration and fisheries management around the world.