Data from: Environmental influences and ontogenetic differences in vertical habitat utilisation of black marlin (Istiompax indica) in the Southwestern Pacific

The black marlin (Istiompax indica), is a highly migratory billfish that occupies waters throughout the tropical and sub-tropical Indo-Pacific. To characterise the vertical habitat use of I. indica, we examined the temperature-depth profiles collected using 102 pop-up satellite archival tags (PSATs) deployed off the east coast of Australia. Modelling of environmental variables revealed location, sea surface height deviation, mixed layer depth, and dissolved oxygen to all be significant predictors of vertical habitat use. Distinct differences in diel movements were observed between the size classes, with larger size classes of marlin (>50 kg) undertaking predictable bounce diving activity during day light hours, while diving behaviour of the smallest size class occurred randomly during both day and night. Overall, larger size classes of I. indica were found to utilise an increased thermal range and spend more time in waters below 150m, than fish of smaller size classes. The differences in the diving behaviour among size classes were suggested to reflect ontogenetic differences in foraging behaviour or physiology. The findings of this study demonstrate, for the first-time, ontogenetic differences in vertical habitat in a species of billfish, and further the understanding of pelagic fish ecophysiology in the presence of global environmental change.黑枪鱼（Istiompax indica）是一种高度洄游的旗鱼，广泛分布于热带及亚热带印度洋-太平洋海域。为阐明I. indica的垂直生境利用模式，本研究对澳大利亚东海岸部署的102个卫星弹出式存档标签（pop-up satellite archival tags, PSATs）所采集的温深剖面数据进行了分析。环境变量建模结果显示，地理位置、海面高度偏差、混合层深度与溶解氧浓度均为垂直生境利用的显著预测因子。不同体长组的昼夜运动模式存在显著差异：体重超过50kg的大型枪鱼在日间会进行可预测的弹跳式潜水活动，而最小体长组的潜水行为则在昼夜均随机发生。总体而言，与小型个体相比，大型I. indica个体的水温适应范围更广，且在150米以下水域停留的时间更长。研究认为，不同体长组间的潜水行为差异，反映了其觅食行为或生理机能的个体发育差异。本研究首次证实了旗鱼物种垂直生境利用的个体发育差异，同时进一步深化了全球环境变化背景下远洋鱼类生态生理学的研究认知。