Table_2_A genomic approach for the identification of population management units for the dolphinfish (Coryphaena hippurus) in the eastern Pacific.docx

In the Tropical Eastern Pacific dolphinfish (TEP) Corypahena hippurus is part of commercial, recreational, and artisanal fisheries and is also caught incidentally by the tuna purse-seine and longline fisheries. Defining the existence of differenced populations in exploited species for being considered independent management units is crucial for conservation plans. However, there is a great uncertainty about the species population genetic structure across the TEP. To investigate it and to identify possible management units for conservation purposes this study was carried out, based on two SNPs datasets of 3867 and 3220 SNPs for young of the year (YOY) and adult individuals, respectively, obtained through NGS protocols. Sampling covered the species’ range distribution in the Tropical Eastern Pacific and was structured into YOY and adult individuals in order to discard the effects of migrating individuals into sampled locations. Our results revealed slight but significant differences among locations occupying the latitudinal limits of the species distribution at transitional areas between tropical and subtropical waters. These areas are characterized by strong seasonal variations in sea surface temperature and limit the prevalence of populations in these extremes. Genetic differences also seem to be related to spatial separation of locations as the northernmost (Los Cabos) and southernmost (Peru) locations including a set of oceanic samples, showed the highest levels of genetic differentiation. Whereas were detected barriers to gene flow among spatially separated locations for YOY individuals probably related to site fidelity, clear limitations to gene flow between Mexico and Central America locations were observed probably related to oceanic circulation in the area. Design management strategies in countries where the dolphinfish is explored is of primary interest to preserve genetic resources. It is necessary to define the existence of genetic differences of populations for species that are highly dependent on environmental factors limiting its distributional range as is the case of the dolphinfish.

东热带太平洋（Tropical Eastern Pacific, TEP）的鲯鳅（Coryphaena hippurus）是商业、休闲及手工渔业的捕捞对象，同时也会在金枪鱼围网和延绳钓渔业中被兼捕。明确被开发物种的分化种群存在性并将其作为独立管理单元，对于保护规划至关重要。然而目前学界对该物种在东热带太平洋范围内的种群遗传结构仍存在较大不确定性。为探究这一科学问题并确定可用于保护的潜在管理单元，本研究基于两套单核苷酸多态性（Single Nucleotide Polymorphism, SNP）数据集开展相关工作：两套数据集分别包含3867和3220个SNP标记，对应当年幼鱼（young of the year, YOY）和成体个体样本，均通过下一代测序（Next-Generation Sequencing, NGS）技术获取。本研究采样覆盖了该物种在东热带太平洋的完整分布范围，并按当年幼鱼和成体个体进行分组，以排除迁徙个体对采样位点造成的干扰。研究结果显示，在位于热带与亚热带水域过渡带、占据物种分布纬度边界的采样位点之间，存在微弱但显著的遗传分化。这类过渡区域以海表温度的强烈季节性变化为特征，限制了种群在分布极端区域的存续。遗传分化似乎还与采样位点的空间距离相关：最北端的洛斯卡沃斯（Los Cabos）和最南端的秘鲁（Peru）位点，连同一组远洋样本，表现出最高水平的遗传分化。针对当年幼鱼个体，在空间分隔的位点间检测到了基因流障碍，这可能与栖息保真度相关；而在墨西哥与中美洲的采样位点之间，也观察到了明显的基因流限制，该现象大概率与该区域的海洋环流有关。针对鲯鳅的开发国家制定针对性管理策略，对保护其遗传资源具有核心意义。对于高度依赖环境因素、分布范围受限的物种（如鲯鳅），明确其种群遗传差异的存在性是十分必要的。