title: Deep-water feeding and behavioral plasticity in Manta birostris revealed by archival tags and submersible observations.
abstract: Foraging drives many fundamental aspects of ecology, and an understanding of foraging behavior aids in the conservation of threatened species by identifying critical habitats and spatial patterns relevant to management. The world's largest ray, the oceanic manta (Manta birostris) is poorly studied and threatened globally by targeted fisheries and incidental capture. Very little information is available on the natural history, ecology and behavior of the species, complicating management efforts. This study provides the first data on the diving behavior of the species based on data returned from six tagged individuals, and an opportunistic observation from a submersible of a manta foraging at depth. Pop-off archival satellite tags deployed on mantas at the Revillagigedo Archipelago, Mexico recorded seasonal shifts in diving behavior, likely related to changes in the location and availability of zooplankton prey. Across seasons, mantas spent a large proportion of their time centered around the upper limit of the thermocline, where zooplankton often aggregate. Tag data reveal a gradual activity shift from surface waters to 100-150m across the tagging period, possibly indicating a change in foraging behavior from targeting surface-associated zooplankton to vertical migrators. The depth ranges accessed by mantas in this study carry variable bycatch risks from different fishing gear types. Consequently, region-specific data on diving behavior can help inform local management strategies that reduce or mitigate bycatch of this vulnerable species.
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA; The Manta Trust, Catemwood House, Corscombe, Dorchester, Dorset, DT2 0NT, UK. Electronic address: j8stewart@ucsd.edu.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Stewart
authors.affiliation: Pelagios Kakunja A.C., Sinaloa 1540, Las Garzas, 23070, La Paz, Baja California Sur, Mexico; Fins Attached, 19675 Still Glen Drive, Colorado Springs, CO 80908, USA.
authors.forename: Edgar Mauricio
authors.initials: EM
authors.lastname: Hoyos-Padilla
authors.affiliation: Pacific Manta Research Group, University of California Davis Bodega Marine Laboratory, 2099 Westshore Rd., Bodega Bay, CA 94923, USA.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Kumli
authors.affiliation: Pacific Manta Research Group, University of California Davis Bodega Marine Laboratory, 2099 Westshore Rd., Bodega Bay, CA 94923, USA; Santa Rosa Junior College, 1501 Mendocino Ave, Santa Rosa, CA 95401, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Rubin
mesh_terms: D000823:Animal Identification Systems; D000818:Animals; D004242:Diving; D056727:Endangered Species; D005247:Feeding Behavior / Q000502:physiology*; D012621:Seasons; D012860:Skates, Fish / Q000502:physiology*
keywords: Deep scattering layer; Diving behavior; Foraging ecology; Manta birostris; Mobulidae