"In general, the survival of these intermediate-aged sharks is critical for sustaining shark populations," said study co-author Dr. Samuel Gruber, Professor at the University of Miami's Rosenstiel School of Marine and Atmospheric Science and Director of the Bimini Biological Field Station, who has been leading the overall lemon shark research program at Bimini since 1978. "Our study suggests that local conservation efforts can help many lemon sharks born at islands like Bimini survive through roughly half of their development to adulthood. Broader scale, sometimes international, management is needed to protect them after they've left their birthplace as adolescents and adults."

Detailed information on how sharks disperse from their birthplace could be very useful for conservation efforts throughout the tropics, given that many tropical shark species are threatened by overexploitation to supply the trade for shark fin soup, for which demand is especially high in Asia. Between 22 and 73 million sharks are killed each year to supply the fin trade, and international management agencies are scrambling for solutions to stem severe shark population declines.

"Our study suggests that many tropical island nations may not have to wait for complex international shark regulations to be established in order to act," said Dr. Chapman. "Their local management efforts could give immature sharks a chance to grow up in relative safety until they are big and 'bad' enough to roam deeper habitats far from home, where broader scale protection becomes more important."

The research team is now extending its study to answer one of the great mysteries of shark biology: do sharks home back to their birthplace as adults? Co-author Dr. Kevin Feldheim of the Field Museum in Chicago, who led the genetics part of the study, said: "This research showed that most of the young sharks left the island by the time they were mature. Now we want to find out if they end up coming back to the place where they were born to breed, much like salmon and sea turtles do."

Source: Stony Brook University