Abstract

This study addresses novel questions on the dynamics of tuna aggregations around floating objects, using echosounder buoys data collected throughout the drifts of newly deployed Drifting Fish Aggregating Devices (DFADs) in the Atlantic Ocean (AO) and Indian Ocean (IO). Time series of presence/absence of tunas were obtained by supervised classification of acoustic data. To avoid biases related to the variability in individual DFAD soak times, a new approach was developed to estimate the average colonization time of new DFADs by tuna aggregations. We showed that tunas colonize DFADs after an average of 16 days in the AO, and 40 days in the IO. Moreover, the analysis indicated that the time span during which tuna aggregations occupy DFADs is driven by a time-independent process with short- and long-term residence modes. On average, DFADs were continuously occupied by tuna aggregations for 6 and 9 days in the IO and AO, respectively. The time between two consecutive aggregations at the same DFAD averaged 9 days in the IO and 5 days in the AO. Throughout their soak time after being colonized, DFADs remained occupied for a larger proportion of time in the AO (63%) than in the IO (45%).

中文翻译：

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漂流鱼聚集设备上的金枪鱼聚集动态：通过商业回声测深仪的浮标观察

摘要

这项研究使用在大西洋（AO）和印度洋（IO）上新部署的漂流鱼聚集设备（DFAD）的整个漂移过程中收集的回声测深浮标数据，解决了有关漂浮物体周围金枪鱼聚集动力学的新问题。通过有声数据的监督分类获得金枪鱼存在/不存在的时间序列。为了避免与单个DFAD浸泡时间的可变性相关的偏差，开发了一种新方法来估计金枪鱼聚集对新DFAD的平均定植时间。我们显示，金枪鱼在AO中平均放置16天，在IO中放置40天之后，在DFAD上定居。此外，分析表明，金枪鱼聚集体占据DFAD的时间跨度是由与时间无关的具有短期和长期居住模式的过程驱动的。一般，DFADs在IO和AO中分别连续6天和9天被金枪鱼聚集所占据。在相同的DFAD中，两次连续聚合之间的时间在IO中平均为9天，在AO中为5天。在定居后的整个浸泡时间内，DFAD在AO（63％）中的停留时间要比IO（45％）更长。