Study: Lemon sharks return to birthplace, exhibiting 'natal homing'

A study by a team of researchers, including two from Stony Brook University, shows sexually mature female lemon sharks return to their place of birth to have their own litter of pups.

The findings, published Thursday in the journal Molecular Ecology, offer the first evidence that lemon sharks exhibit "natal homing" despite having spent years away from their nursery.

Finding that sharks, widely thought to be a roaming species, have a homing ability to return to specific places could help nations and regions implement specific fishing bans or create sanctuary areas to protect the species.

The study is based on research dating to 1995, when researchers in the Bahamian island of Bimini began tagging and taking tissue samples of lemon sharks. The sharks, named for their color, tend to stay where they are born, seeking protection from predators in the local mangroves until they are about 5 years old.

The females become sexually mature between 15 and 17 years old and return to Bimini when carrying their young, on average about every two years. They can have as many as 18 pups at a time, and the brood can have between two and five fathers, said Kevin Feldheim, manager of Chicago's Pritzker Laboratory for Molecular Systematics and Evolution and the study's lead author.

Many returned consistently. "We're realizing these nursery areas are really vital for these populations," he said. "There's some females that have been giving birth [in the research area] the entire course of the study."

"There are a lot of conservation implications of these scientific findings," said Ellen K. Pikitch, a professor at Stony Brook's School of Marine and Atmospheric Sciences and executive director of the Institute for Ocean Conservation Science based there.

The findings could be applicable to other species, she said.

In 2011 the Bahamas enacted anti-poaching legislation protecting more than 40 species of sharks from hunting. Shark fins are a prized delicacy, and with two dorsal fins, lemon sharks often fall prey.

"I really think that there is not a species of shark on this planet that would be rejected for its fin," Pikitch said.

Palau, the Maldives and Honduras also ban shark hunting.

"National efforts to rein in the shark fishing industry by many countries are likely to benefit homing shark species, like lemon sharks," Stony Brook assistant professor Demian Chapman, also a study author, said in a news release.