Swarms of up to 200 lemon sharks off the Florida coast have enabled marine biologists to get face-to-face with the still-enigmatic species. Scroll down to below the video player to read details of this unusual shark behavior.

July 26, 2005—Each year dramatic swarms of up to several hundred lemon sharks gather near Jupiter, Florida. The aggregations offer scientists a unique opportunity to meet adults face-to-face and are believed to be part of the animal's reproductive cycle.

Like salmon and certain other marine species, lemon sharks (Negaprion brevirostris) return to their natal grounds to give birth.

"If a whole population was less than 100 or 200 animals, you might expect to see sharks with twelve fins," said Samuel "Doc" Gruber, a marine biologist at the University of Miami. Small populations, he said, could lead to inbreeding.

Yet lemon sharks appear normal. "This perplexed us," Gruber noted.

To avoid inbreeding problems, the sharks appear to have developed a mating strategy as yet unobserved in other shark species: Though female lemon sharks return to their birthing grounds each year, males remain nomadic.

The strategy ensures genetic diversity among different lemon shark populations. It may also have spawned the phenomenon of large lemon shark gatherings, like the ones found near Jupiter, Florida. Such gatherings guarantee that the two sexes get together.

—Brian Handwerk

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