Tiger Shark News

If you've seen an up-close photograph of a tiger or lemon shark, we'd bet it was taken at Tiger Beach, an area close to Grand Bahama and visited by shark diving operators from the Bahamas as well as American liveaboards from Fort Lauderdale, FL. The sharks, mainly lemon and tiger sharks, are there year-round, but why?

Recently researchers from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and the University of New England performed in-water ultrasound imaging technology on live tiger sharks and took blood samples for hormone analysis to determine the reproductive status of females.

"Using the same ultrasound imaging technology used on pregnant women, we discovered Tiger Beach was important for females of different life stages, and that a high proportion of tiger sharks were pregnant during winter months," said Professor James Sulikowski.

Study co-author Neil Hammerschlag, a research assistant professor at the UM Rosenstiel School and Abess Center for Ecosystem Science and Policy, said, "Our data suggests that Tiger Beach may function as a refuge habitat for females to reach maturity, as well as a gestation ground where pregnant females benefit from calm, warm waters year-round that help incubate the developing embryos and speed up gestation."

The study has been published in the recent edition of the Journal of Aquatic Biology.

Meanwhile, down under, a female tiger shark was tagged near Exmouth in Western Australia. Nominally "Catalina," she made her way north into the Timor Sea before being tracked all the way south, a distance of around 3000 nautical miles, where she has become the first tiger tracked onto the continental shelf of South Australia, an amazing feat because the water there is thought to be too cold for a tiger shark, says Dr. Mark Meekan from the Australian Institute of Marine Science. "But these big sharks can be full of surprises."

Scientists attach radio tags to track sharks. Each time a tagged shark's dorsal fin breaks the surface of the water, it transmits a signal to a satellite, which in turn transmits an estimated geo location. You can follow Catalina, the tiger shark, on the Global Shark Tracker page at http://www.ocearch.org/profile/catalina/