Science in Seconds: Meet Steve Kajiura

Every fall, thousands of blacktip sharks migrate south to the southeast Florida coast to escape the colder temperatures. It’s the largest migration in U.S. coastal waters — and it may be impacted by climate change.

Stephen Kajiura, Ph.D., professor, Charles E. Schmidt College of Science, has studied these sharks since 2010, counting them from planes and drones, and monitoring them from boats to record size, sex and tag individuals to track movements.

Kajiura has previously reported as many as 15,000 blacktip sharks on any given day, with the densest aggregation of sharks reported at more than 2,100 sharks.

According to recent research, Kajiura and his team found that male sharks travel all the way from Palm Beach, Fla., to Long Island, N.Y. Female sharks appear to travel shorter distances, depending on whether they are pregnant or not. For instance, female blacktip sharks reproduce every other year and so one reproductive year is followed by a year of rest. Resting females travel farther north, while pregnant females stay closer to the nursery grounds where they then give birth.

Kajiura said monitoring migration is important because the aggregation locations may be shifting north as a result of global climate change, according to research his team’s research.

Sharks have been migrating down to southeast Florida for thousands of years. The very recent change in water temperature means that we will no longer have this large seasonal influx of these top predators every year, Kajiura said. As a result, the prey fish populations will not receive an annual culling — or spring cleaning — when the top-level predators fail to arrive. “This could have cascading effects throughout the entire ecosystem, and we simply don't know how this may affect populations around here,” he said.