Some sharks return to the same sites to breed for decades

Some sharks return to the same sites to breed for decades

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Some species of shark return to the same breeding grounds for decades at a time, and live longer than previously thought.

Nurse shark
Nurse shark

Scientists with the New England Aquarium found that nurse sharks, Ginglymostoma cirratum, returned to the waters off the Dry Tortugas, 70 miles (113km) from Key West, to mate for up to 28 years. The Dry Tortugas has been known as a courtship and mating site for nurse sharks since 1895.

A 30-year (1992–2021) study documented long-term site fidelity to this area, with data from 137 adult sharks.

Known individuals returned in up to 16 different mating seasons and over periods of up to 28 years, indicating that the sharks' lifespan extends well into the forties, rather than about 24 years as previously believed.

Of all the sharks returning to the site, nearly 60 percent were monitored for more than 10 years and 13 percent were monitored for more than 20 years.

Males arrived annually in May and June and departed in July, whereas females arrived biennially or triennially in June, with a secondary peak in site use in September and August, likely associated with thermoregulation during gestation.

The scientists wrote that this evidence of long-term mating site fidelity of this shark population reveals the importance of identifying and protecting mating sites for this and other elasmobranch species.