Sharks Crowd Florida Coast

SCIENCE

Scroll down for a quick list of key resources in our Teachers’ Toolkit, including today’s MapMaker Interactive map.

Discussion Ideas

According to the Christian Science Monitor article and the South Florida Sun-Sentinel video, thousands of blacktip sharks are making an annual migration to South Florida. Where are the sharks migrating from? Take a look at today’s MapMaker Interactive map for some help.
- This population of blacktip sharks spends most of the year in the waters off North Carolina. Some blacktip populations can make their way to Long Island, New York, and a few lost souls have found their way as far north as Massachusetts. “It looks like there’s a correlation between global warming and their expanding range,” says one biologist. “They’re moving further north to find their ideal temperature.”

Why do you think the blacktips head to Florida every January or February? Take a look at today’s MapMaker Interactive map and this activity for some help.
- Every winter, blacktips migrate south, where sea-surface temperatures are warmer. Biologists think temperature may be only one reason for the sharks’ southern sojourn, however: “The temperature decreases, so perhaps that drives the blacktip sharks’ prey [mostly small fish, such as mullet] further south, leading the predators to follow. But also correlated with changing temperatures is the shifting day length. It’s impossible to tease it all apart.”

Blacktips usually turn up near Florida coasts in mid-January. Why are they so late this year?
- The unusually warm temperatures associated with the El Niño weather pattern probably have something to do with the sharks’ tardy arrival.

Why are the sharks swimming so close to shore?
- It’s their natural habitat. Unlike deep-water sharks (such as the terrifying frilled shark) or open-ocean sharks (such as Lydia, the great white tracked traversing the entire Atlantic), blacktips stick close to shore. Most blacktip sharks don’t venture into waters deeper than about 30 meters (98 feet). They even have a high tolerance for brackish water, so can stick close to shallow estuaries and deltas.

Are swimmers at risk from the shivers of sharks?
- No, swimmers probably aren’t in terrible danger, although no one recommends deliberately antagonizing any sharks. The biologist studying blacktip migration says “For the most part, these sharks are really skittish, so when you get in the water, they’re going to scatter and go away.”