Warming waters are causing less blacktip sharks to migrate to South Florida

BY GENNA NORDLING

College students aren’t the only tourists Florida beaches expect to see during Spring Break. Blacktip sharks make their way to South Florida every year around this time, but there has been a decline in number of sharks that are migrating in the past few years.

Blacktip sharks start heading south when waters drop to a temperature of 71 degrees Fahrenheit, traveling from North Carolina to South Florida. These sharks have a vital role in the ecosystem when they arrive in the south. According to Florida Atlantic University associate professor and internationally renowned shark researcher Stephen Kajiura, Ph.D., blacktip sharks ‘spring clean’ and eat all of the weak and ill fish which keeps the coral reefs and sea grasses healthy.

Usually, tens of thousands of sharks find their way to South Florida. Kajiura and his team count more than 15,000 sharks in a group, meaning that anyone in the water could be at least 60 feet away from a shark. But last year, there was an extreme decrease in the amount of sharks that made it past Central Florida.

“Last year, we saw a dramatic decline in the number of blacktip sharks that migrated south,” Kajiura said. “In fact, it was so low that we estimated the population to be about one-third of what we have seen in previous years.”

“Last year, we saw a dramatic decline in the number of blacktip sharks that migrated south,” Kajiura said. “In fact, it was so low that we estimated the population to be about one-third of what we have seen in previous years.”

According to National Geographic, the sharks are not traveling to South Florida because the waters of the Carolinas and Central Florida are warm enough for them to be comfortable. Last year’s winter had warmer waters than usual, never dropping below 73.4 degrees Fahrenheit. This year, water temperatures have dramatically raised to 78.8 degrees Fahrenheit.

Kajiura suspects that because of these warming waters, the black tip shark population will move further north. He believes that the warming waters are linked to global warming and climate change. National Geographic also states that according to Victor Saba (a marine biologist at the National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center), the waters off the coast of the northeast United States have warmed faster than 99 percent of the rest of the worlds waters. If these sharks continue to stop further north, there could be serious problems.

“They’re just simply stopping when they reach their optimum water temperature,” Kajiura said. “That might have ramifications throughout the ecosystem … You might have an abundance of sick or diseased fish here that are not being cleaned out.”

Estuaries, coral reefs, shallows waters and other areas blacktip sharks could become either overpopulated or riddled with disease if the migratory population continues to drop.

If the number of sharks migrating continue to deplete, this will disrupt the all of the ecosystems they are apart of. As a predator, these sharks control overpopulation of their prey and all of the organisms below them in the food chain. Estuaries, coral reefs, shallows waters and other areas blacktip sharks could become either overpopulated or riddled with disease if the migratory population continues to drop.

“We want to make sure that these snowbirds come back to South Florida,” Kajiura said. “Because if they don’t, it will have a huge ecological impact in this region.”

Photo courtesy of  National Geographic