For the first time, researchers have been able to record in near real-time the migration of a pregnant scalloped hammerhead shark (Sphyrna lewini) from the Galápagos Islands in Ecuador to Isla del Coco in Costa Rica, located over 435 miles (700 kilometers) away.
In a truly international collaboration, the Charles Darwin Foundation’s shark ecology project, the Galapagos National Park Directorate (GNPD), Save Our Seas Foundation Shark Research Center, and Guy Harvey Research Institute at Nova Southeastern University (USA) have teamed up to study the migrations and population genetics of the world’s largest scalloped hammerhead shark aggregation.
For the first time, researchers have been able to record in near real-time the migration of a ... [+] pregnant scalloped hammerhead shark (Sphyrna lewini) from the Galápagos Islands in Ecuador to Isla del Coco in Costa Rica, located over 700 km away.
gettyThe scalloped hammerhead shark is a globally endangered migratory species a globally endangered species that inhabit both coastal and oceanic areas of the circumtropical seas. The neonates, juveniles, adult females, and adult males often occupy different habitats but information about their movements and habitat use is quite fragmentary. Enter a special hammerhead shark: Cassiopeia. Measuring about 8.2 feet (2.5 meters) long, this pregnant female was tagged in February of this year during an expedition to Darwin Island. Named after Charles Darwin himself, the northern-most island of the Galápagos archipelago is well-known among ocean-lovers for its diverse and abundant marine wildlife… this includes hammerheads, since it is their seasonal home and draws hundreds of individuals!
Thirteen tags were deployed to investigate for the migratory routes pregnant hammerheads undertake to nursery areas along the central and southern Americas (this would actually be the second year in a row). Satellite tracking data revealed that after swimming north of Darwin Island for about 10 days, Cassiopeia started swimming eat until she reached Isla del Coco. Also known as Cocos Island, it is thought of as the little Galapagos of Costa Rica and declared World Heritage Site by UNESCO in 1997.
School of scalloped hammerheads swimming over a reef and one breaks from the main school. Darwin ... [+] Island.
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The trek Cassiopeia made between the two islands means she covered around 390 nautical miles (700 km) in just under 14 days, travelling an approximate of 28 nm (50 km) per day. While previous studies have documented inter-island movements of hammerheads using passive acoustic tags, the tags weren’t able to capture the precise pathways the sharks would take. With these tags, though, scientists were able to see exactly the route they went.
“Better understanding the annual reproductive migrations of pregnant hammerhead sharks is vital to inform an urgently needed regional conservation approach aimed at reverting ongoing population declines across the Tropical Eastern Pacific,” said Dr. Pelayo Salinas de León, Senior Marine Scientist at the Charles Darwin Foundation and Save Our Seas Foundation Conservation Fellow. “Cassiopeia’s journey is not over yet: from Isla del Coco she still has to travel another 700 km or so to reach the continental coast where she will give birth to her babies within mangrove bays. Just imagine being 9 months pregnant of 20-30 baby sharks, and having to swim over 1500 km, dodging thousands of fishing hooks and nets along the way… and then swim back! If we want to save the scalloped hammerhead shark from extinction, we really need to protect these superhero mums as they migrate across the region.”
Prof. Mahmood Shivji, director of the Guy Harvey Research Institute and Save Our Seas Foundation Shark Research Center at Nova Southeastern University, agrees: “There is no more important group to protect than these pregnant females as they try to run the gauntlet of often illegal and unregulated fishing activity between the Galapagos and their birthing sites along the mainland. The data being collected in this study will be key for establishing a flexible management system that provides this protection at precisely the right places and times.”
The scalloped hammerhead shark is a globally endangered migratory species a globally endangered ... [+] species that inhabit both coastal and oceanic areas of the circumtropical seas.
gettyCurrently, there is limited data regarding the reproductive biology of the scalloped hammerheads in Ecuadorian waters, limiting the development of appropriate management measures here. But a recent study has attempted to document their reproductive biology in the central-eastern Pacific Ocean, recording a total 1,664 specimens off Manta, Ecuador from 2003-2009. Caught by local commercial fisheries, they found that females were being more frequently caught (the sex ratio was 1 male to 1.8 females). Any gravid females that were caught had 16-22 embryos and measured anywhere from 246–298 cm in total length (TL, from tip of snout to the end of dorsal caudal lobe of a shark’s tail in its natural position; this is often used as a standard measurement in the shark science).
So, what does this mean for Cassiopeia? Well, she could be in trouble. Last year the Galápagos Islands had a “massive” fleet of Chinese fishing vessels in their waters, with numbers fluctuating to over 350 before they left by mid-October to fish farther south. If she stays within Ecuador's exclusive economic zone (EEZ), she’s safe. But that’s the problem with migratory sharks… they don’t just stay in one place. While Cassiopeia is safe, for now, her future is very unclear.