VIDEO: Tracking An Endangered Hammerhead Shark For Thousands Of Kilometres

A hammerhead shark being measured. Image: Mauricio Hoyos

The precise movements of a young hammerhead shark have been tracked for the first time over a 10-month period.

The study, published in journal Animal Biotelemetry, reveals important gaps in current efforts to protect these endangered sharks and suggests key locations which should be protected.

Hammerhead sharks, which have recently received new protections from the UN Convention on the Conservation of Migratory Species of Wild Animals, are experiencing drastic population declines in excess of 90% in several parts of world.

Scalloped hammerhead sharks, found in the Gulf of California, Mexico, are particularly susceptible to being caught by fishing nets while moving into the open sea, but little information exists on their exact movements.

Researchers from the Centro Interdisciplinario de Ciencias Marinas, Mexico, and the University of California, Davis, travelled out into the Gulf of California by boat and collected three live juvenile hammerhead sharks.

At the base of their pelvic fins they inserted small electronic tracking devices, able to calculate position and depth, and then released the young sharks back into the water.

Only one shark, a female which had grown to 123 cm, was recaptured 10 months later by local fisherman after they identified the visible tag and reward notice during fishing.

After the tracking device was removed and the shark released, the downloaded data revealed a wealth of information about her 3,350 km journey.

Study author Mauricio Hoyos says the key to protecting this species is detecting their nursery grounds and protecting them in their more vulnerable stages.

The young female hammerhead was found to swim within a school of fellow hammerheads at an offshore island during the day, but migrated away at night, diving to greater depths to feed on fish and squid, sometimes as deep as 270 metres.

The research suggests that juvenile female hammerheads are trading off the risks of greater exposure to predators in the open sea, in exchange for the opportunity to get offshore as early as possible and grow big quickly.

By doing this they can jockey for position, assert dominance in the schools, establish social rank and increase their reproductive potential.

Watch the video of the researchers tagging and releasing the hammerhead sharks:

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