Cortisol is recognized as a physiological indicator of stress in fish. However, this hormone is typically measured in plasma samples. In this study, cortisol content was evaluated for the first time in the scales of tropical tuna. The sample included 20 skipjack tuna (Katsuwonus pelamis) and 25 yellowfin tuna (Thunnus albacares) collected in the Atlantic (the Gulf of Guinea off the Ivory Coast) and the Indian Ocean (off Reunion Island), and their scales were analyzed using an ELISA test. The results indicated that on average, cortisol concentration (1) did not show any geographical pattern, (2) was independent of fish size, and (3) was significantly higher in skipjack (mean 4.75 ± 6.56 ng g⁻¹) than in yellowfin (mean 1.65 ± 1.85 ng g⁻¹), although the difference was mainly due to four skipjack individuals. Larger datasets would be needed to confirm any species difference in cortisol concentration. The particularly high cortisol concentration observed in four individuals may be due to fish from different schools, suggesting the need for future sampling from free-swimming schools to investigate intra- and inter-school variability in cortisol concentration. This study opens the door for future research, including the collection of scales on tagged individuals, to investigate the links between chronic stress and behavior in these species.

皮质醇被认为是鱼类压力的生理指标。然而，这种激素通常在血浆样品中测量。在这项研究中，首次对热带金枪鱼的皮质醇含量进行了评估。样本包括在大西洋（象牙海岸附近的几内亚湾）和印度洋（留尼汪岛附近）收集的20 条鲣鱼 ( Katsuwonus pelamis ) 和 25 条黄鳍金枪鱼 ( Thunnus albacares )，并使用 ELISA 分析了它们的鳞片测试。结果表明，平均而言，皮质醇浓度 (1) 没有显示任何地理模式，(2) 与鱼的大小无关，并且 (3) 鲣鱼（平均 4.75 ± 6.56 ng g ^-1）显着高于黄鳍鱼（平均 1.65 ± 1.85 ng g ^-1)，尽管差异主要是由于四个鲣鱼个体。需要更大的数据集来确认皮质醇浓度的任何物种差异。在四个个体中观察到的特别高的皮质醇浓度可能是由于来自不同学校的鱼，这表明未来需要从自由游泳学校取样以调查皮质醇浓度的校内和校际变异性。这项研究为未来的研究打开了大门，包括收集标记个体的尺度，以调查这些物种的慢性压力与行为之间的联系。