Young Lemon Sharks Stay Close to Home

It seems young lemon sharks that live in the waters around the Bahamas are homebodies. Recent research has revealed that these "teenage" sharks stay close to their birthplace as they mature.

Previously, little was known about the wanderings of the sharks after they reached 3 years of age. Scientists were uncertain whether they dispersed into new territory as they gained experience or if they lingered close to their nursery sites. These new findings reveal that more than half of teenage lemon sharks hang-out in the waters near their former nurseries.

The long-term study was conducted by scientists from the Institute for Ocean Conservation Science at Stony Brook University, University of Miami, and Field Museum of Chicago.

From 1995 to 2007, the researchers sampled sharks in Bimini, Bahamas, a cluster of subtropical islands on the western edge of the Great Bahamas Bank, about 86 kilometers east of Miami. The two largest of the islands in the area, North Bimini and South Bimini, form an arch of land that shelters a shallow, mangrove-fringed lagoon. There are several lemon shark nurseries within the lagoon, sites where the sharks give birth and where young sharks congregate until they are old enough and large enough to set off on their own.

Each summer during that time period, the researchers spent 3 weeks capturing, measuring, tagging and releasing lemon sharks from the nursing sites in the lagoon. In subsequent years, they recaptured the sharks to determine which individuals had moved on to new territory and which had remained close to their home territory.

Lemon sharks don't reach reproductive age until at least ten years of age. It's critical that conservationists understand the "missing teenage years" during a shark's development in order to ensure young sharks mature and join the breeding population.

Refs:
CHAPMAN, D., BABCOCK, E., GRUBER, S., DIBATTISTA, J., FRANKS, B., KESSEL, S., GUTTRIDGE, T., PIKITCH, E., & FELDHEIM, K. (2009). Long-term natal site-fidelity by immature lemon sharks at a subtropical island Molecular Ecology, 18 (16), 3500-3507 DOI: 10.1111/j.1365-294X.2009.04289.x

Photo © Matthew D. Potenski / MDP Photography.