Research Reveals Remarkable Longevity and Site Fidelity Among Sharks

A groundbreaking study has discovered that certain shark species, particularly nurse sharks, return to their breeding grounds for extended periods, demonstrating longevity beyond previous estimates. Conducted by researchers at the New England Aquarium, this investigation focused on nurse sharks inhabiting the waters of the Dry Tortugas, situated approximately 70 miles from Key West, Florida.

The findings suggest that nurse sharks may mate in the same locations for as long as 28 years, with lifespans extending into their 40s, rather than the earlier belief of around 24 years. Published in the journal PLOS ONE, this research represents the longest ongoing study of shark mating behaviours, offering new insights into the significance of environmental factors in their reproductive cycles.

Nick Whitney, a senior scientist and co-author of the study, remarked, “This is the first instance demonstrating long-term fidelity to a mating ground. Observing natural shark behaviours in their habitat is rare, and witnessing mating activities is particularly exceptional.”

While it has been known for centuries that nurse sharks utilise the Dry Tortugas as a breeding site, the extent of their return remained unclear. Researchers tagged 118 sharks between 1993 and 2014, finding that more than two-thirds returned to the same breeding grounds in subsequent seasons. Notably, nearly 60% of tracked sharks were monitored for over a decade, with 13% observed for more than 20 years.

David Shiffman, a marine biologist at Arizona State University not involved in the study, noted the implications for shark conservation: “Understanding that some species remain in the same habitat year after year is truly fascinating.”

The Dry Tortugas, a remote archipelago in the Gulf of Mexico, is a favourite destination for divers and birdwatchers. However, the area’s status as a breeding ground for nurse sharks could be jeopardised by the recent impact of Hurricane Ian in September. Researchers have yet to ascertain whether their underwater monitoring stations survived the storm or if the sharks have returned, as female sharks typically move into shallower waters in September and October to prepare for birthing, according to Ryan Knotek, an associate scientist and co-author of the study.