Tuna aggregation dynamics at Drifting Fish Aggregating Devices: a view through the eyes of commercial echosounder buoys
|Author(s)||Baidai Yannick1, 2, Dagorn Laurent1, Amandè Monin J2, Gaertner Daniel1, Capello Manuela1, Proud Roland|
|Affiliation(s)||1 : MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
2 : Centre de Recherches Océanologiques (CRO), 29 rue des pêcheurs, BPV 18, Abidjan, Côte d’Ivoire
|Source||Ices Journal Of Marine Science (1054-3139) (Oxford University Press (OUP)), 2020-12 , Vol. 77 , N. 7-8 , P. 2960-2970|
|WOS© Times Cited||1|
|Keyword(s)||absence times, associative behaviour, colonization times, Drifting Fish Aggregating Devices (DFADs), echosounder buoys, residence times, tropical tunas|
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%).