Each year, by the end of January, a shiver of blacktip sharks — named for the black spots on the tips of their fins and tails — arrive in numbers totaling more than 10,000 to the coastal waters along Palm Beach County.
This year, the migration was caught on video, from above, by biological sciences professor for Florida Atlantic University Stephen Kaijura, who then posted it to Facebook. "[The migration] is getting a lot of coverage this year because I posted that crazy video," he said.
"There are literally tens of thousands of sharks right adjacent to shore, and certainly many more than that, farther off shore, that we're simply not seeing in video surveys."
These particular blacktips grow to be about 6 feet long (their Pacific cousins are a bit larger) and will remain in Florida until the end of March, at which time they begin their trek back north, resting in waters around the Carolinas for the summer. Although the sight of shark-infested waters is alarming, many of the beaches don't close, because the sharks are just far enough from the coast, and aren't so interested in humans anyway, says Kaijura.
"The sharks can tell that you're a person, not a fish, so the number of bites on people is relatively low down here. When you consider that there are literally tens of thousands of sharks, and not many bites, it's a testament that these sharks are not out to get you."
Kaijura and other scientists will tag the sharks with transmitters as they pass by, in an attempt to learn more about migratory patterns. They've noticed in recent years that some blacktips are reaching waters typically thought to be too cold for the sharks, but are now warmer due to a rise in sea level temperature, such as those around New York's Long Island.