Data from: Ontogenetic resource utilization and migration reconstruction with δ13C values of essential amino acids in the Cynoscion acoupa otolith

1. With the increasing anthropogenic impacts on fish habitats, it has become more important to understand which primary resources sustain fish populations. This resource utilization can differ between fish life stages and individuals can migrate between habitats in search of resources. Such lifetime information is difficult to obtain due to the large spatial and temporal scales of fish behaviour. The otolith organic matrix has the potential to indicate this resource utilization and migration with δ13C values of essential amino acids (EAAs), which are a direct indication of the primary producers. 2. In a proof-of-concept study, we selected the Acoupa weakfish, Cynoscion acoupa, as a model fish species with distinct ontogenetic migration patterns. While it inhabits the Brazilian mangrove estuaries during juvenile stages, it moves to the coastal shelf as an adult. Thus, we expected that lifetime resource utilization and migration would be reflected in δ13CEAA patterns and baseline values in C. acoupa otoliths. 3. By analysing the C. acoupa otolith edges across a size range of 12 to 119 cm, we found that baseline δ13CEAA values increased with size, which indicated an estuarine to coastal shelf distribution. This trend is highly correlated with inorganic δ13C values. The δ13CEAA patterns showed that estuarine algae rather than mangrove-derived resources supported the juvenile C. acoupa populations. Around the juvenile size of 40 cm, resource utilization overlapped with those of adults and mean baseline δ13CEAA values increased. This trend was confirmed by comparing otolith core and edges, although with some individuals potentially migrating over longer distances than others. 4. Hence, δ13CEAA patterns and baseline values in otoliths have great potential to reconstruct ontogenetic shifts in resource use and habitats. The insight could aid in predictions on how environmental changes affect fish populations by identifying the controlling factors at the base of the food web.

1. 随着人类活动对鱼类栖息地的干扰日益加剧，明确维持鱼类种群的核心营养资源已成为亟待解决的科学问题。鱼类的资源利用策略会随生活史阶段发生显著分化，且个体为获取资源会在不同栖息地间迁移。但由于鱼类行为的时空尺度跨度极大，获取覆盖完整生命周期的相关信息难度极高。耳石（otolith）有机基质可通过必需氨基酸（essential amino acids, EAAs）的δ¹³C值反映鱼类的资源利用与迁移情况——该同位素比值可直接指示初级生产者的碳源特征。
2. 在本次概念验证研究中，我们选取阿卡帕弱鱼（Acoupa weakfish，*Cynoscion acoupa*）作为模式物种，该物种具有典型的发育型迁移模式：幼体阶段栖息于巴西红树林河口，成体则迁移至大陆架海域。据此我们推测，阿卡帕弱鱼耳石中的δ¹³C_EAA模式与基线值，能够反映其整个生命周期的资源利用与栖息地迁移过程。
3. 我们对体长12至119 cm的阿卡帕弱鱼耳石边缘开展同位素分析后发现，基线δ¹³C_EAA值随体长增长而升高，这表明鱼类的栖息环境从河口逐渐向大陆架转变，该趋势与无机碳的δ¹³C值高度相关。δ¹³C_EAA模式显示，幼体阿卡帕弱鱼种群的主要营养来源为河口藻类，而非红树林衍生资源。当幼体体长约40 cm时，其资源利用策略与成体重叠，且基线δ¹³C_EAA平均值出现上升。通过对比耳石核心与边缘的同位素信号，我们验证了这一趋势，不过部分个体的迁移距离可能长于其他个体。
4. 综上，耳石中的δ¹³C_EAA模式与基线值，具备重建鱼类资源利用与栖息地选择的发育转变的巨大潜力。该研究结果可通过识别食物网底层的调控因子，助力预测环境变化对鱼类种群的影响。