Evidence and patterns of tuna spawning inside a large no-take Marine Protected Area Scientific Reports

The Phoenix Islands Protected Area (PIPA), one of the world's largest marine protected areas, represents 11% of the exclusive economic zone of the Republic of Kiribati, which earns much of its GDP by selling tuna fishing licenses to foreign nations. We have determined that PIPA is a spawning area for skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares) tunas. Our approach included sampling larvae on cruises in 2015-2017 and using a biological-physical model to estimate spawning locations for collected larvae. Temperature and chlorophyll conditions varied markedly due to observed ENSO states: El Nino (2015) and neutral (2016-2017). However, larval tuna distributions were similar amongst years. Generally, skipjack larvae were patchy and more abundant near PIPA's northeast corner, while Thunnus larvae exhibited lower and more even abundances. Genetic barcoding confirmed the presence of bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tuna larvae. Model simulations indicated that most of the larvae collected inside PIPA in 2015 were spawned inside, while stronger currents in 2016 moved more larvae across PIPA's boundaries. Larval distributions and relative spawning output simulations indicated that both focal taxa spawned inside PIPA in all 3 study years, demonstrating that PIPA is protecting viable tuna spawning habitat. Grant no. NA14OAR4320158

凤凰群岛保护区（Phoenix Islands Protected Area, PIPA）是全球规模最大的海洋保护区之一，占基里巴斯共和国专属经济区（exclusive economic zone）的11%——基里巴斯的国内生产总值（Gross Domestic Product, GDP）很大一部分来自向外国出售金枪鱼捕捞许可。本研究确认凤凰群岛保护区为鲣鱼（Katsuwonus pelamis）、大眼金枪鱼（Thunnus obesus）与黄鳍金枪鱼（Thunnus albacares）的产卵场。本研究方法涵盖2015-2017年科考航次中的幼鱼采样工作，以及利用生物-物理模型（biological-physical model）估算所采集幼鱼的产卵位置。受厄尔尼诺-南方涛动（El Niño-Southern Oscillation, ENSO）状态影响，海域水温与叶绿素浓度存在显著差异：2015年为厄尔尼诺事件，2016-2017年为中性状态。但各年份的金枪鱼幼鱼分布格局较为相似。总体而言，鲣鱼幼鱼呈斑块状分布，在保护区东北角海域丰度更高；而金枪鱼属幼鱼的丰度则更低且分布更为均匀。遗传条形码（genetic barcoding）技术确认了大眼金枪鱼与黄鳍金枪鱼幼鱼的存在。模型模拟结果显示，2015年在保护区内采集的绝大多数幼鱼均为在保护区内产卵所得，而2016年较强的海流将更多幼鱼带至保护区边界之外。幼鱼分布与相对产卵产出的模拟结果表明，在本研究覆盖的3个年份中，两类目标类群均在凤凰群岛保护区内产卵，这证实凤凰群岛保护区正保护着具有生存活力的金枪鱼产卵栖息地。资助编号：NA14OAR4320158