Correlated Random Walk of tuna in arrays of Fish Aggregating Devices: A field-based model from passive acoustic tagging

For centuries fishers have exploited the propensity for tuna to associate with floating objects, yet reasons and mechanisms behind this behavior remain unclear. The number of man-made objects (FADs, Fish Aggregating Devices) undergone a dramatic increase in recent decades, development industrial purse seine fishing. However, current knowledge does not allow evaluation consequences on ecology tuna. Here, we developed model movements an array FADs, using passive acoustic tagging data. was built four behavioral rules: (1) when no FAD is perceived, exhibit random search behavior, (2) individuals can orient directly they perceive it (within given orientation radius), (3) associative dynamics follow daily rhythm (4) Continuous Residence Time (CRTs – time spend at by tuna) are independent from previous Absent (CATs- between two consecutive CRTs). based only parameters: swimming speed, path sinuosity, distance loss term account natural fishing mortality events. calibrated 70±10 cm yellowfin (Thunnus albacares), acoustically tagged different networks anchored FADs (Oahu, Hawaii, U.S.A. Mauritius) densities. Our results show that reproduce spent traveling (i.e., away FADs), as well total fish (total residence time) both study sites. parameter sets best experimental data correspond steering radius 2 5 km, sinuosity (correlated walk parameter) 0.9 0.995 rates 1 3% per day. This model, thus parameterized, could be used future studies predict arrays densities provide scientific advice their management. same approach modeling marine terrestrial animals detected near aggregation