The devil ray in the details

Many individual islands and states in the western and central Pacific had their own protections for the charismatic reef manta (M. alfredi), beloved by tourists. But devil rays don’t generally draw tourism revenue like mantas do, according to Guy Stevens, founder and chief executive of the U.K.-based NGO Manta Trust, who said he was encouraged by their inclusion in the new WCPFC measure.

Stevens said he hopes tourism will eventually foster the same widespread love for mobulids that dolphins receive, where a single undercover photo of abuse can cause a Twitter cyclone of outrage. He said manta and devil rays need the same stringent level of protection that the IATTC has provided for dolphins: Dolphins have bycatch quotas, and onboard observers document each ship’s compliance. Fishing boats steer clear of dolphins when planning routes. Crew members jump into the water to guide trapped dolphins over the top of purse seine nets because they know that tuna will go low, but dolphins will stay near the top — the kind of information yet to be gathered about manta and devil rays.

As a result of the IATTC’s 1999 dolphin conservation agreement, the management body says bycatch rates for dolphins dropped from 132,000 in 1986 to less than 1,000 in recent years.

But to duplicate that level of success for mantas and devil rays, scientists and fishers have much to learn about them. For instance, scientists don’t have much data on mobulids’ migratory paths, or the locations of their feeding grounds and cleaning stations that could help fishing boats avoid them. Any increase in tagging and documentation resulting from the new measure will help scientists fill those and other information gaps, as well as understand what’s working and what isn’t in the safe-handling guidelines.

Mobula rays in a Sri Lankan fish market, in 2018. Image © Simon Hilbourne | Manta-Trust.

As long as fisheries management bodies show a willingness to work with the science, Stevens said he expects the various regional manta and devil ray protection measures to undergo continuous refining as the data come in. So far, according to Stevens, managers are willing. The IATTC has already scheduled a meeting with manta scientists, a year from now, to assess and refine the mobulid protection measures it implemented in 2015.

The WCPFC measure is a doorway to answers. Will more gently handled and quickly released rays have any better chances of surviving getting caught? What kind of compliance, observation and enforcement practices are realistic for the western and central Pacific?

The measure will take effect in January 2021. While it could be a long wait for manta and devil rays, it gives scientists and NGOs a year to gather more data. According to Dimmlich, the commission requested a report on mobulids based on observer-gathered data later this year, and if feasible, a detailed assessment of the region’s mobulid stock by 2023.

“We have to go through the scientific process,” Stevens said.

And if the measure doesn’t look like it is saving mobulids?

“We go back to them and say this is not good enough.”

Banner image: A reef manta ray (Mobula alfredi) in the Maldives. Image © Guy Stevens | Manta Trust.

Marianne Messina is a conservation journalist focusing on wildlife and sustainable farming issues. Over her career, she has contributed hundreds of freelance articles to print and web news outlets and magazines.

Correction 2/24/20: This story was updated to reflect a recent change in title for Wetjens Dimmlich, director of fisheries management for the Pacific Islands Forum Fisheries Agency.

Citations:

Francis, M. P., & Jones, E. G. (2016). Movement, depth distribution and survival of spinetail devilrays (Mobula japanica) tagged and released from purse-seine catches in New Zealand. Aquatic Conservation: Marine and Freshwater Ecosystems27(1), 219-236. doi:10.1002/aqc.2641

White, W. T., Corrigan, S., Yang, L., Henderson, A. C., Bazinet, A. L., Swofford, D. L., & Naylor, G. J. P. (2017). Phylogeny of the manta and devilrays (Chondrichthyes: mobulidae), with an updated taxonomic arrangement for the family. Zoological Journal of the Linnean Society182(1), 50-75. doi:10.1093/zoolinnean/zlx018

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