Some sharks return to the same sites to breed for decades

Some species of shark return to the same breeding grounds for decades at a time, and live longer than previously thought, scientists studying the animals off Florida say.

Scientists with the New England Aquarium found that nurse sharks returned to the waters off the Dry Tortugas, 70 miles (113 kilometers) from Key West, to mate for up to 28 years. They also found that the sharks' life span appears to extend at least into their 40s, rather than about 24 years as previously believed.

The researchers published their findings in October in the journal PLOS ONE as part of the world's longest running study of shark mating behavior. The research sheds new light on the way sharks breed and the role their environments play in their reproduction, said Nick Whitney, a senior scientist with the aquarium and a co-author of the study.

“This is the first example that has shown long-term use of a mating ground,” Whitney said. “To observe natural shark behavior in the wild is incredibly rare to begin with and to observe mating behavior is really unusual.”

Scientists have known nurse sharks have used the waters off the Tortugas as a breeding ground since at least the late 19th century, but the question of whether the sharks returned to the area lingered. The researchers with the aquarium tagged 118 sharks from 1993 to 2014 and found that more than two-thirds returned to the breeding grounds in subsequent mating seasons.

The scientists wrote that this evidence of long-term fidelity to one site “reveals the importance of identifying and protecting mating sites for this and other” species.

Members of the research team said they did not guess the same animals would continue mating at the site for years at a time. Of all the sharks returning to the site, nearly 60% were monitored for more...