Nickels Catherine F, Muhling Barbara A, Portner Elan J, Snodgrass Owyn E, Dewar Heidi
University of California, Santa Cruz, Institute of Marine Sciences' Fisheries Collaborative Program, Santa Cruz, California, United States of America.
Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, California, United States of America.
PLoS One. 2025 Sep 11;20(9):e0331436. doi: 10.1371/journal.pone.0331436. eCollection 2025.
Juvenile albacore tuna (Thunnus alalunga) undertake long migrations across the North Pacific that they fuel by feeding in the California Current System (CCS) during the summer. The CCS is a highly dynamic system, which can lead to differences in foraging success that may be indicated by differences in body condition. Assessed through stomach content analysis, albacore diet composition by mean proportional weight showed high interannual variability including some years characterized by large increases in consumption of anchovy (2011 = 81%, 2017, 2022) and sardine (Sardinops sagax, 2022). We used a generalized additive model (GAM) to investigate the impact of albacore length, month of collection, diet composition, and environmental conditions on albacore muscle energy content. Two proxies for muscle energy content, the carbon to nitrogen ratio (C:N) and ash free dry weight (AFDW), were positively but weakly correlated. Albacore C:N increased with month, body size, and upwelling in the first half of the year, and decreased with increasing sea surface temperature. The mean energy density of prey and chlorophyll-a concentration were not important predictors of muscle energy content, indicating that albacore may be resilient to changes in prey composition and productivity. Sea surface temperature was the most important predictor of muscle energy content, which suggests that marine heat waves and projected future warming in the CCS may have detrimental effects on albacore body condition or the value of the CCS as a foraging habitat.
幼年长鳍金枪鱼（Thunnus alalunga）会在北太平洋进行长途洄游，它们在夏季通过在加利福尼亚洋流系统（CCS）觅食来获取能量。CCS是一个高度动态的系统，这可能导致觅食成功率的差异，而这种差异可能通过身体状况的不同表现出来。通过胃内容物分析评估，按平均比例重量计算，长鳍金枪鱼的饮食组成显示出较高的年际变异性，包括某些年份以凤尾鱼（2011年=81%，2017年、2022年）和沙丁鱼（Sardinops sagax，2022年）消费量大幅增加为特征。我们使用广义相加模型（GAM）来研究长鳍金枪鱼的体长、采集月份、饮食组成和环境条件对其肌肉能量含量的影响。肌肉能量含量的两个指标，碳氮比（C:N）和无灰干重（AFDW）呈正相关但相关性较弱。长鳍金枪鱼的C:N在上半年随月份、体型和上升流增加，随海面温度升高而降低。猎物的平均能量密度和叶绿素a浓度不是肌肉能量含量的重要预测指标，这表明长鳍金枪鱼可能对猎物组成和生产力的变化具有恢复力。海面温度是肌肉能量含量最重要的预测指标，这表明海洋热浪以及CCS未来预计的变暖可能对长鳍金枪鱼的身体状况或CCS作为觅食栖息地的价值产生不利影响。
