Acoustic and behavioral strategies of dolphins in relation to fishing vessel traffic in the Southern Gulf of Mexico Data Set

Behavioral and acoustic plasticity of bottlenose dolphins allow them to explore a variety of habitats and to develop strategies to overcome the increasingly demanding anthropogenic pressures. Bottlenose dolphins are known to compete with artisanal fishing along the southwestern coast of the Gulf of Mexico, but the extent of marine traffic impact on the dolphins is unknown. We investigated dolphin behavioral dynamics through unmanned aerial vehicles (UAV) and acoustic recordings in two zones off Alvarado, Veracruz, Mexico, with high (HVP) and low-vessel presence (LVP). Our results show that at the HVP-zone, located at the mouth of the Alvarado lagoon and with a greater abundance of prey, dolphins focus their behavioral budget on feeding, with higher emission rates of echolocation trains. Conversely, at the LVP-zone, which is located northwest and southeast of the lagoon mouth, their behavioral repertoire is more varied (dolphins move, feed, socialize, and rest equally), and they emit not only large amounts of echolocation trains, but also whistles at higher emission rates. Our findings suggest a zoning strategy through a compensatory mechanism that has allowed dolphins to develop a level of tolerance to fishing activities and marine traffic within their feeding areas, by reducing the size of their groups (and individual interactions) while prioritizing acoustic and surface behavior when in presence of vessels. By using this trade-off strategy, dolphins may remain at the site and continue taking advantage of the resources, at the expense of long-term effects, which remain to be investigated.