Tuesday, September 2, 2014

MCAF at Work: Tagging Giants, Part 2

This post is one of a series on projects supported by the Aquarium’s Marine Conservation Action Fund (MCAF). Through MCAF, the Aquarium supports researchers, conservationists and grassroots organizations all around the world as they work to address the most challenging problems facing the ocean.  

Part 1 of this series focused on how scientists tag these giants. Here's more about the scientific tagging project from guest blogger Josh Stewart of the Manta Trust

The Aquarium’s Marine Conservation Action Fund helped support the satellite tagging of manta rays off the coast of Mexico, led by Josh Stewart of the Manta Trust.

Understanding how these gentle giants move around in and use their environment is a pressing and unanswered question. Manta rays are threatened globally by targeted fisheries and bycatch, much of which is driven by the gill plate trade (read more here). Currently we know almost nothing about the population structure and connectivity of oceanic manta populations, which have significant implications for the impacts that fisheries are having on mantas, as well as the practicalities of effective conservation and management action. Luckily, mantas are protected from direct catch under Mexican law, but they are still impacted by harmful fisheries interactions and bycatch in Mexican waters.

Tagging oceanic manta rays

We know of two manta hotspots in Pacific Mexico: the Revillagigedo Archipelago, long a favorite of dive tourists, and Bahia de Banderas, where we've recently discovered what seems to be a sizeable manta population. One of our goals is to determine whether these two 'hotspots' are part of a single, linked population that migrates seasonally between the two regions, or if they represent separate populations. Evidence of fisheries interactions, such as gear entanglement, scars from fishing lines, and missing cephalic and pectoral fins, is more frequent in mantas observed at the coastal hotspot in Bahia de Banderas, suggesting that mantas using this area may be more susceptible to bycatch or other negative impacts of fisheries.

Understanding the linkage between these regions, as well as the habitats that the mantas here are using and visiting frequently, will help us generate strategies for reducing and mitigating these impacts. Furthermore, the tag tracks will show us how large the geographic ranges of these populations are and, importantly, whether they are staying within Mexican waters or traveling to regions where mantas are not protected.

While we'll be biting our nails until the tags pop off and transmit their data in November, the New England Aquarium is taking the opportunity to properly prepare for the satellite tracks by naming the two mantas that are currently sporting some new MCAF-funded fashion accessories. Stay tuned for details on how you can suggest names for these mantas and vote on your favorites! We'll keep you updated on where the mantas went and what this means for manta conservation come this fall.

Josh Stewart is the Associate Director of the Manta Trust, a PhD student at Scripps Institution of Oceanography, and a grantee of the Aquarium’s Marine Conservation Action Fund.

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