Scope and Consequences of Variability in the Early Life History Traits of a Caribbean Coral Reef Fish

在底栖海洋生物的远洋幼体阶段发生的事件可在调节开放种群方面发挥重要作用。从远洋幼体阶段到底栖幼体阶段(定居和变态)之间的过渡通常被认为是珊瑚礁鱼等许多底栖海洋鱼类生命的关键时期，但这些阶段之间的联系相对较少受到关注。幼虫期表现出的生物学特性不仅会影响幼虫的存活，还会影响后续幼虫阶段的招募和存活。早期生活史(ELH)特征的自然变异模式、早期幼年死亡率和与特征相关的存活率完全未知。我们目前还不知道哪些幼虫存活下来成功定居，以及哪些幼虫在珊瑚礁上存活了早期生命，包括耗费巨大的蜕变过程。虽然有关温带系统中幼鱼的ELH特征能带来更高存活率的生态学理论已经开发出来，但这一理论很少被推广到幼鱼的过渡阶段，而且关于热带物种(如珊瑚礁鱼)ELH特征与存活率之间的关系的数据也很少。这项实地研究旨在调查一种常见的加勒比海珊瑚礁鱼类ELH特征的自然变异模式，以及这种变异对从浮游生物向珊瑚礁过渡期间幼鱼和幼鱼生存的影响。将在佛罗里达群岛的几个季节(6个月)对新招募的多个海链藻队列进行普查和收集。和水文条件，以确定环境条件、ELH特征和招聘成功之间的关系。新兵将从高密度和低密度的栖息鱼类的复制地点收集，以研究不同的生长和死亡情况如何进一步影响新兵的ELH特征的分布。检查后期幼虫和幼虫的耳石记录将能够识别幼虫生长速度、年龄大小、定居时的大小和年龄以及幼虫生长速度等群体内、群体间和地点间的差异。此外，还将测量后期幼体和新出现的幼体(在礁石上1天)的特定群组条件指数。对耳石记录的纵向和横截面分析将揭示生长较快、较大或较大的幼虫或条件较高的幼虫优先存活，以及大型招募活动是否由具有特殊ELH特征的幼虫或新兵组成。一系列密集的青少年普查将提供每日特定年龄的死亡率，这些死亡率与耳石衍生的ELH性状分析将定义生长、存活和ELH性状选择性丧失之间的关系。因此，这项实地研究将是第一次广泛的现场调查ELH特征与幼体和幼年珊瑚鱼存活的关系。这项研究的结果将有助于我们理解珊瑚礁鱼类生活史上这一重要过渡阶段的动态，以及导致这些开放种群中补充数量变化的因素。

Events occurring during the pelagic larval stage of benthic marine organisms can play an important role in the regulation of open populations. The transition between the pelagic larval stage and the benthic juvenile stage (settlement and metamorphosis) is generally recognized as a critical period in the life of many benthic marine fishes such as coral reef fishes, yet the linkage between these phases had received relatively little attention. Biological traits exhibited during the larval stage can influence not only larval survival, but also the recruitment and survival of subsequent juvenile stages. Patterns of natural variability in early life history (ELH) traits, early juvenile mortality, and trait--related survival are entirely unknown. We currently have no knowledge of which larvae survive to settle successfully, and which of those then survive the early life on the reef, including the energetically expensive process of metamorphosis. While ecological theory concerning the ELH traits that confer higher survival has been developed for larval fishes in temperate systems, rarely has this theory been extended across the transition to juveniles, and very few data are available on the relationship between ELH traits and survival for tropical species such as coral reef fishes.This field study is designed to investigate patterns of natural variability in the ELH traits of a common Caribbean coral reef fish and the consequences of this variation to the survival of young larvae and juveniles during the transition from the plankton to the reef. Multiple cohorts of newly recruited Thalassoma bifasciatum will be censused and collected from sites in the Florida Keys over several seasons (6 mos.) and hydrographic conditions to identify the relationship between environmental conditions, ELH traits, and recruitment success. Recruits will be collected from replicate sites with high and low densities of resident fishes to examine how variable growth and mortality further influence the distribution of ELH traits of recruits. Examination of the otolith record of late-stage larvae and young juveniles will enable the identification of within--cohort, among-cohort, and among-site differences in ELH traits such as larval growth rates, size-at-age, size and age at settlement, and juvenile growth rates. In addition, cohort-specific condition indices will be measured for late-stage larvae and emerging juveniles (1 d on the reef). Longitudinal and cross-sectional analyses of otolith records will reveal whether faster-growing, larger or older larvae, or larvae of higher condition preferentially survive, and whether large recruitment events are composed of larvae or recruits with particular ELH traits. An intensive series of juvenile censuses will provide daily age-specific mortality rates, which together with the otolith-derived ELH trait analyses will define the relationship between growth, survival, and selective loss of ELH traits. As such, this field study will be the first broad in situ investigation of the relationship between ELH traits and the survival of larvae and young juvenile reef fishes. Results of this study will contribute to our understanding of the dynamics of this important transitional phase in the life history of coral reef fishes and the factors contributing to recruitment variability in these open populations.