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Some species of sharks return to the same breeding grounds decades at a time and live longer than previously thought, scientists study the animals. Florida say
Scientists with the New England Fisheries found that nurse sharks returned from Dry Tortugas, about 70 miles (113 kilometers) off Key West, to mate for up to 28 years. They also found that the life span of sharks is extending to at least 40 years, instead of about 24 years as previously believed.
The researchers published their findings in the journal PLOS ONE in October as part of the world’s longest study of shark mating behavior. The research sheds new light on how sharks reproduce and the role their environments play in their reproduction, said Nick Whitney, a senior scientist at the fishery and co-author of the study.
“This is the first example of long-term use of mating land,” Whitney said. “Observing natural shark behavior in the wild is incredibly rare and observing mating behavior is truly extraordinary.”
Scientists have known that nurse sharks have used Tortugas’ waters as a breeding ground since at least the late 19th century, but the question of whether the sharks have ever returned to the area remains. Researchers with the fishery tagged 118 sharks from 1993 to 2014 and found that more than two-thirds returned to breeding grounds in subsequent mating seasons.
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This evidence of long-term fidelity to a site “highlights the importance of identifying and protecting mating sites for this and other species,” the scientists wrote.
Members of the research team said they did not expect the same animals to continue mating at the site for years at a time. Of all sharks returning to the site, nearly 60% were tracked for more than 10 years and 13% were tracked for more than 20 years.
David Shiffman, marine biologist Arizona The state university, which was not involved in the study, said the work will open new perspectives on sharks and how they migrate and use habitat.
That could be a key to helping protect them, he said.
“Some well-known shark species are highly migratory, constantly crossing oceans. So it’s fascinating to learn that other species are homebodies that use the same habitat year after year,” Schiffman said.
The Dry Tortugas are a remote group of islands in the Gulf of Mexico that are popular with divers and birdwatchers. The area’s status as a breeding ground for nurse sharks may be affected by its direct impact. Hurricane Ian In September, Whitney said.
Scientists have yet to determine whether the underwater observatories survived the storm. They still don’t know if the sharks are back. Female sharks come into the shallows in the area to prepare to give birth in September and October, said Ryan Nodek, associate scientist at the fishery and study co-author.
Whitney said the vulnerability of the site is a good reason to protect both sharks and their breeding stock.
“These sharks have a strong desire to return to this state,” he said. “It’s a shark that was once thought to be a shark’s sitting couch potato. It turns out they’re very active.”
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