Finding Bull Shark Nurseries
by Safina Center Fellow Jasmin Graham
A graphic created for the North Carolina Bull Shark Project, a collaboration between Minorities in Shark Sciences and Encounter NC that aims to further our understanding of bull shark nurseries. ©MISS
Minorities in Shark Sciences (MISS) is working with scientists and community members to understand how bull sharks use inland waters as nurseries in both Florida and North Carolina. After years of focused research on manatees, attention has shifted to bull sharks in Crystal River, Florida, where little data currently exists regarding their population and nursery habitats. MISS Member Dr. Alyssa Andres posits that Crystal River could be a crucial nursery for this species on Florida's west coast, especially as water conditions evolve. She started a new research initiative in collaboration with MISS that aims to quantify and monitor the local bull shark population. The project involves the local community, particularly fishermen, who provide valuable insights into the sharks’ daily presence and activities. For this project, Alyssa is tracking baby bull sharks using acoustic telemetry.
The project in North Carolina was actually initiated by community members and shark enthusiasts who were curious about the shark populations in their area. Encounter NC is a small Instagram page where community members share photos, information and encounters with sharks in a fun and engaging way. It’s led to a lot of interest in understanding the sharks in the area. Encounter NC decided to partner with MISS to study these sharks in greater depth.
A baby bull shark found in Crystal River, Florida. ©Dr. Alyssa Andres
Fortunately, one of our Friends of MISS, Dr. Chuck Bangley, had already laid the groundwork for understanding the movements of bull sharks along the coast of NC in his previous research. Thanks in large part to his research, Pamlico Sound in North Carolina is now recognized as a key nursery area, potentially the northernmost for bull sharks along the U.S. Atlantic coast, previously thought to extend only to the Indian River Lagoon in Florida. We plan to follow up on this research by using satellite tags to track the movements of pregnant bull sharks as they move around North Carolina.
Both sites provide an interesting way to study how climate change is affecting bull sharks. While widespread along coasts, bull sharks typically establish nurseries in select locations, making the discovery of nursery areas in Crystal River and Pamlico Sound critical for their conservation. With climate change leading to rising temperatures, understanding how these changes affect local wildlife becomes increasingly urgent. Crystal River's unique characteristics make it a prime location for bull shark nurseries. As Florida's second-largest spring system, it offers a stable thermal refuge, crucial for the survival of young sharks. The consistent temperatures in Crystal River reduce the risks associated with migrating to find suitable conditions, which can expose young sharks to predators and temperature fluctuations.
Chuck’s study was the first to link environmental factors to the colonization of Pamlico Sound as a nursery habitat for bull sharks, highlighting a significant increase in juvenile shark presence. From 2003 to 2011, only six juvenile bull sharks were captured, but from 2011 to 2016, that number surged to 53, indicating a dramatic rise in their abundance. Researchers found that increasing water temperatures and salinities during summer months correlated with this rise in juvenile populations. By comparing these two study sites, we hope to gain more insight into the behaviors of bull sharks.