Mixed stock analysis of juvenile green turtles aggregating at two foraging grounds in Fiji reveals major contribution from the American Samoa Management Unit Scientific Reports

In this study we assessed the breeding population, or Management Unit (MU), origin of green turtles (Chelonia mydas) present at Yadua Island and Makogai Island foraging grounds in Fiji, central South Pacific. Based on analysis of mitochondrial (mt) DNA sequences from 150 immature green turtles caught during surveys carried out in 2015-2016, we identified a total of 18 haplotypes, the most common being CmP22.1 (44%) which is a primary haplotype characterizing the American Samoa breeding population. Results of a Bayesian mixed-stock analysis reveals that the two foraging grounds are used by green turtles from the American Samoa MU (72%, Credible Interval (CI): 56-87%), New Caledonia MU (17%, CI: 6-26%) and French Polynesia MU (7%, CI: 0-23%). The prominence of the contribution we found from the American Samoa MU compared to that of French Polynesia, both which have historic telemetry and tagging data showing connectivity with Fijian foraging areas, may reflect the current relative abundance of these two nesting populations and draws attention to a need to update population surveys and identify any significant nesting in Fiji that may have been overlooked.

本研究针对南太平洋中部斐济的亚杜阿岛（Yadua Island）与马科盖岛（Makogai Island）的绿海龟（Chelonia mydas）觅食地，对栖息于此的绿海龟的繁殖种群——即管理单元（Management Unit, MU）——的来源展开评估。本研究基于2015-2016年野外调查捕获的150只未成熟绿海龟的线粒体（mitochondrial, mt）DNA序列分析，共鉴定出18种单倍型，其中占比最高的为CmP22.1（44%），该单倍型是表征美属萨摩亚繁殖种群的核心单倍型。贝叶斯混合种群分析结果显示，这两处觅食地的绿海龟分别来自美属萨摩亚管理单元（MU，72%，可信区间（Credible Interval, CI）：56%~87%）、新喀里多尼亚管理单元（MU，17%，CI：6%~26%）以及法属波利尼西亚管理单元（MU，7%，CI：0%~23%）。相较于法属波利尼西亚管理单元，本研究观测到美属萨摩亚管理单元的种群贡献占比更为显著；二者均有历史遥测与标记数据证实其与斐济觅食区存在种群连通性，这一结果或可反映当前这两个筑巢种群的相对丰度差异，同时也提示亟需更新现有种群调查方案，并排查斐济境内可能被遗漏的重要筑巢位点。