Scientists Document First Evidence of Shark Swimming Between Cocos Island National Park and Las Gemelas Seamount

Scientists Document First Evidence of Shark Swimming Between Cocos Island National Park and Las Gemelas Seamount

Researchers tag a thresher shark at Las Gemelas Seamount to track its movements.

Written by Executive Director Todd Steiner

For the past 12 years, Turtle Island Restoration Network’s work at Cocos Island National Park to tag turtles and sharks with our colleagues MigraMar has focused on understanding where highly migratory species go when they leave protected “no-take” zones of the Park.

We have shown a minimum of five endangered species (two sea turtle species and three shark species) move between Cocos Island and Galapagos National Park – located approximately 400 miles south – along an underwater mountain range thousands of feet beneath the surface, known as the Cocos Ridge. The Cocos Ridge contains many underwater peaks called seamounts — most of which have never been explored. Cocos and Galapagos Islands are the highest points on this mountain range, extending beyond the ocean surface, and in the case of Cocos, to a height of 2,080 feet. 

Now, for the first time, we have documented a scalloped hammerhead shark moving persistently between Cocos Island National Park and the Las Gemelas Seamount, emphasizing the need to create swimways between marine protected areas to protect the migratory route of hammerhead sharks and other species that have shown to move between biodiversity hotspots. 

In 2015, with the generosity and help of Ray Dalio and the Dalio Foundation, we joined a team of marine scientists and sailed to Cocos Island aboard its research vessel the Alucia. Using two onboard submarines, we visited Las Gemelas Seamount and placed an underwater acoustic listening device on its pinnacle 600 feet below the surface. We also tagged a thresher shark.

A year later, we returned and retrieved the receiver and downloaded the data.  

Published today in Revista de Biología Tropical, the data showed a scalloped hammerhead shark we tagged at Cocos Island National Park made persistent movements between Cocos Island and Las Gemelas Seamount, a distance of approximately 40 miles. In addition, the thresher shark stayed put while at Las Gemelas, indicating resident behavior.

Movements of scalloped hammerhead shark ID 22437 between Cocos Island National Park and the Seamounts Marine Management Area during May 2015 and May 2016. Dotted lines suggest the potential shark’s trajectory.

This data is now being used to promote the expansion of a no-take zone that connects Cocos Island and Las Gemelas and to demonstrate the importance of the Cocos Ridge. Furthermore, this information is being used to advocate for a much larger marine protected area, known as the Cocos-Galapagos Swimway, that connects Costa Rica’s Cocos Island with Ecuador’s Galapagos Island. 

We thank all of our TIRN members and supporters for providing the resources necessary to advance  this research and help us better advocate for stronger protections for sharks, sea turtles and other highly migratory marine species!

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