Blacktip Shark Facts: Climate Change Lowers Ocean Migration

Climate change has drastically reduced the number of blacktip sharks migrating down the Atlantic coast to South Florida, posing a threat to the environmental health of the region.

Researchers at Florida Atlantic University have been tracking what should be an enormous migration, during which sharks leave cooling waters up north and play an important role in the tropical ecosystem. Instead, researchers found a sharp decline in the migrating population.

According to the university, last year's roving gang was about one-third of what it should have been, and this year's numbers represent a big drop as well. In the past, shark counters may have caught sight of up to 15,000 sharks in a single day in southern Florida, but the group has not reached that bar in 2018.

blacktip-shark-oahu
As the ocean water gets warmer, blacktip sharks are changing their migration patterns, threatening important tropical ecosystems. James P. McVey/NOAA

Observations have been made in part by taking photos and video while flying above shark groups, then manually counting the number of animals in a single frame. They have also used drones to collect the footage.

"We want to make sure that these snowbirds come back to South Florida, because if they don't, it will have a huge ecological impact in this region," researcher Stephen Kajiura said in a statement.

According to FAU, blacktips are needed to "weed out weak and sick fish species, helping to preserve coral reefs and sea grasses."

The International Union for Conservation of Nature said the shark's diet consists of bony fish and crustaceans like crabs and shrimp.

Although the migrations are changing, blacktips—whose scientific name is Carcharhinus limbatus—are still listed as "near threatened" on the group's threatened species list. That category is on the less severe end of the scale, above only the animals that are of "least concern."

While the new migration research focuses on blacktips in the western Atlantic, the sharks are found in other areas around the world, including the Mediterranean, the eastern Atlantic and around Australia.

The torpedo-shaped sharks can be identified by their gray bodies and white bellies as well as lines on their sides that look like a wedge or the letter "Z," the U.S. National Oceanic and Atmospheric Administration explained. Their common name comes from the black tips on their tail, pectoral and dorsal fins. Blacktips can be as long as 6 feet.

The sharks might help scientists better understand climate change and how it is changing the marine ecosystem. According to FAU, "since water temperatures affect the migration of these sharks, studying the correlation of water temperatures and their migration patterns provides … a powerful predictive tool."

blacktip-shark-group
As the ocean water gets warmer, blacktip sharks are changing their migration patterns, threatening important tropical ecosystems. Albert Kok/public domain