Manta Ray Tagging with Propspeed
To find out whether New Zealand mantas are indeed resident year-round, the Department of Conservation and Conservation International teamed up to satellite-tag these elusive creatures, with support from Oceanmax.
New Zealand fishermen have spotted the giant oceanic manta ray (Manta birostris) off the coast of the North Island for over a decade now, but observations were generally limited to the summer months. This led many scientists to believe that they were migrating populations passing through New Zealand waters. Recent studies of oceanic mantas in Mexico, Peru, Indonesia and Sri Lanka show them to be much more “site-attached,” or resident, than previously thought, raising the strong possibility that the mantas seen off the North Island's east coast are actually resident year-round. This is further supported by the fact that oceanic mantas are only rarely sighted in neighboring Australia and the islands surrounding New Zealand, including New Caledonia and Tonga.
To test that assumption, the New Zealand Department of Conservation and Conservation International, with support from Oceanmax, deployed satellite tags on local mantas from March 20 to 23, 2017. These satellite tags were to remain on the mantas for up to 12 months, allowing marine biologists to see exactly where they were going during winter. The tags, deployed using a pole spear, temporarily lodge in the manta’s dorsal fin by way of a titanium dart and release after a pre-programmed period, in this case 12 months.
While the tags remain attached, they record depth and temperature readings every 10 seconds. They also take GPS fixes anytime the tag’s antenna breaks the surface, as when mantas rise to feed or cruise. It is hoped that the results will conclusively show if the mantas are indeed here year-round while providing more detail about their movements. Findings will be important for population management and potentially developing local tourism around this endangered, worldwide-protected species. Manta watching is growing rapidly around the world, as is their popularity as the world’s smartest fish.