  Based on the data gathered by echo-sounder buoys attached to drifting Fish
Aggregating Devices (dFADs) across tropical oceans, the current study applies a
Machine Learning protocol to examine the temporal trends of tuna schools'
association to drifting objects. Using a binary output, metrics typically used
in the literature were adapted to account for the fact that the entire tuna
aggregation under the dFAD was considered. The median time it took tuna to
colonize the dFADs for the first time varied between 25 and 43 days, depending
on the ocean, and the longest soak and colonization times were registered in
the Pacific Ocean. The tuna schools' Continuous Residence Times were generally
shorter than Continuous Absence Times (median values between 5 and 7 days, and
9 and 11 days, respectively), in line with the results found by previous
studies. Using a regression output, two novel metrics, namely aggregation time
and disaggregation time, were estimated to obtain further insight into the
symmetry of the aggregation process. Across all oceans, the time it took for
the tuna aggregation to depart from the dFADs was not significantly longer than
the time it took for the aggregation to form. The value of these results in the
context of the "ecological trap" hypothesis is discussed, and further analyses
to enrich and make use of this data source are proposed.
