About This Project

Blacktip sharks (Carcharhinus limbatus) aggregate by the thousands in the warm nearshore waters of Southeast Florida each winter. However, these massive aggregations are comprised exclusively of males. Where are the females? We will travel to their summertime mating/birthing areas to instrument females with acoustic transmitters to delineate their migratory route and identify critical habitat. Knowing the distribution of the entire population is essential for effective management.

Ask the Scientists

What is the context of this research?

Blacktip sharks exhibit a well-known, but poorly studied, seasonal migration along the US eastern seaboard. They migrate from summer mating/birthing grounds in the Carolinas down to Southeast Florida where they form massive aggregations in nearshore waters from January-April. Their migration closely correlates with water temperature and, as global water temperatures have increased, their northern range has expanded correspondingly. As a result, their migration is now up to 50% farther than it was historically. This imposes a significant energetic burden on the sharks and increases the travel duration.

Our work has revealed that the huge winter aggregations of blacktips in Southeast Florida are comprised entirely of males. Which raises the question, “Where are all the females?”

What is the significance of this project?

It is impossible to effectively manage a population if you don’t even know where half the population is for most of the year. Because we encounter only males in Southeast Florida, we lack data for the females. Blacktip sharks are harvested commercially and targeted recreationally, so, to provide effective management, it is vital to know their migratory route and where the entire population is distributed throughout the year.

As the northern limit of their migration expands due to global warming, the sharks will also establish new critical habitat which must be identified to provide appropriate conservation.

This project is significant because it will address a large data gap on the distribution of the female blacktip sharks.

What are the goals of the project?

This project will determine the migratory route of female blacktip sharks in the Western Atlantic. We will travel to known blacktip mating/birthing areas in South Carolina where we can be sure to encounter females. We will instrument 12 female sharks with 6 year acoustic transmitters. The instrumented sharks will be detected by an array of acoustic receivers distributed along the coast from Florida to Nova Scotia. Data from these receivers is shared freely among the researchers who are members of the collaborative networks. The movements of the female blacktips will be reconstructed from the receiver detections and their seasonal migratory pattern delineated over several years. From this we will be able to determine critical habitat used by these sharks throughout the entire year.