Sharks on Spring Break

The snowbirds aren’t the only ones who return yearly to Florida, attracted by its warm coastal waters. Blacktip sharks annually migrate from as far away as North Carolina during the winter and thousands of them come within yards of South Florida beaches. The sharks normally arrive in mid-January and leave by the end of March but this winter their arrival was late. This might be because of the El Nino that caused an unseasonably warm winter on the East Coast.

The sharks typically grow to five or six feet long. They were named Blacktip for the black markings on the tips of their fins. They are among the most common species to bite people and are believed to be responsible for most of the shark attacks in Florida, none of which have been fatal according to the National Oceanic and Atmospheric Administration.

Stephen Kajiura, a professor of biological sciences at Florida Atlantic University, has been studying shark migration since 2011. He said this year’s estimate of 10,000 to 12,000 sharks is probably an underestimate of how many sharks are in Florida waters because it only includes the ones that are visible in shallow waters.

Since December, Kajiura has been flying in a small plane from the southern end of Miami beach to Jupiter to survey blacktip numbers and locations. In an aerial video, he captured the ocean filled with tiny black dots hovering just off the shore for 80 miles from Miami to Jupiter Inlet. The black dots were blacktip sharks.

Kajiura and his team are also tagging sharks. They catch a shark, then implant a transmitter immediately and send it on its way. The transmitters emit a signal that can be picked up by undersea listening posts operated along the east coast by the Atlantic Cooperative Telemetry Network. The signals are picked up by receivers, which record the presence of that particular shark.

Dr. Kajiura is interested in what the sharks are doing when they are in Florida and what their movements are. Also where they go when they leave, how far up the coast do they go?

The sharks are now on their way to waters off of Georgia and the Carolinas and some may go as far as New York. The female sharks will give birth around June, mate again, then move back to Florida in the winter.

Photo courtesy of Florida Atlantic University

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