Bycatch mitigation from the sky: using helicopter communication for Mobulid conservation in tropical tuna fisheries

March 2024

Jennifer L. Waldo,  Ernesto Altamirano-Nieto, Donald Croll, Marta D. Palacios, Nerea Lezama-Ochoa, Jon Lopez, Gala Moreno, Stefany Rojas-Perea & Melissa R. Cronin

Keywords: Purse seine • Management • Eastern Pacific Ocean • Stakeholder Knowledge • Elasmobranch • Conservation Technology

Summary: In tuna fisheries, bycatch of non-target species, particularly vulnerable marine vertebrates like manta and devil rays, is a concern. Efforts to reduce mobulid bycatch mainly focus on post-capture measures. A novel strategy involves communication between tuna purse seine fishing vessels and spotter helicopters to detect mobulids before capture. A survey of 33 individuals operating in the eastern Pacific Ocean suggests helicopter crews can sight and identify mobulids, and they often communicate sightings to vessels. This approach could enable scalable bycatch detection and improve mobulid conservation efforts.

Abstract

“The incidental capture of non-target species (bycatch) in tuna fisheries impacts some marine vertebrates, particularly species with vulnerable life histories such as manta and devil rays (mobulids). There is broad interest in reducing mobulid bycatch in tuna purse seine fisheries, with existing efforts mainly focusing on reducing post-capture mortality rates. We explore a novel potential pre-capture mobulid bycatch avoidance strategy for the tuna purse seine fishery using communication between fishing vessels and associated spotter helicopters. We conducted a survey of tuna purse seine helicopter pilots, spotters, and fishers operating in the eastern Pacific Ocean (n = 33) to ascertain the ability of helicopter crew to detect mobulids prior to capture and communicate bycatch avoidance with vessel crew. Results indicate over half of the helicopter crew report being “always” or “sometimes” able to sight and identify mobulids and that helicopter crew regularly communicate mobulid sightings to the vessel already. Given that an average of 63% of class-6 vessel trips between 2017 to 2022 carried onboard helicopters, our results suggest that helicopter-vessel communication could be feasible and scalable for mobulid bycatch detection, enabling potential bycatch avoidance and early alerts for proper handling protocols. We also identify the potential use of helicopter detection to improve research efforts for mobulid conservation (e.g., data collection of population and habitat observations). This study is the first to investigate the utility of helicopter-vessel communication as a bycatch mitigation strategy for elasmobranchs and identifies research and management directions that could be further investigated to avoid bycatch of mobulids.”

Photos From The Field

Author Affiliations

  • Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University

  • Long Marine Lab, University of California Santa Cruz

  • Mobula Conservation

  • Inter-American Tropical Tuna Commission

  • Instituto Politécnico Nacional

  • The Manta Trust

  • Institute of Marine Sciences, University of California Santa Cruz

  • Ecosystem Science Division, National Oceanic and Atmospheric Administration (NOAA) Southwest Fisheries Science Center

  • International Seafood Sustainability Foundation

  • Nicholas School of the Environment, Duke University

Funded by

  • Thomas G. Scott Publication Funds

  • Western Division of the American Fisheries Society Small Project Grant

  • Undergraduate Research in Science & Technology Endowment

  • Stevenson College Student Research Project Award from the University of California, Santa Cruz