Drone imaging of elasmobranchs

Drone imaging of elasmobranchs: Whale sharks and golden cownose rays co-occurrence in a zooplankton hot-spot in southwestern Sea of Cortez

Martín G.Frixione, Miguel de J .Gómez García, Marco F.W. Gauger

ABSTRACT:

The golden cownose ray (Rhinoptera steindachneri) and the whale shark (Rhincodon typus) are two elasmobranch species commonly found in Bahía de La Paz, Baja California Sur, Mexico. There are no records of the species sharing the same sites, as their prey, ecology and migration sites normally deviate. Both are listed as endangered and vulnerable species, respectively, under Mexican and international regulations. We took images by a quad-copter near Mogote Beach and recorded whale sharks during late July, alongside a group of golden cownose rays, although earlier research suggests that the main whale shark feeding season starts in late August or September. These recordings showed for the first time, the co-occurrence of these two vulnerable elasmobranch species while feeding possibly simultaneously. This indicates that there might be a relation between the presence of the two species and the interannual variability in zooplankton abundance. The latter may have implications for possible resource overlapping, a current topic in elasmobranch research. Furthermore, these findings highlight the usefulness of drones when capturing biological data. This information is important in the understanding of the ecology and trophic interactions of threatened species and is a step forward towards their understanding and conservation.

Food Webs, Volume 24, September 2020, e00155, DOI: 10.1016/j.fooweb.2020.e00155

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