A new study based on long-term monitoring data demonstrates significant differences in growth between nurse sharks off the coast of Miami and those living just across the Gulf Stream.
A new study from the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science shows that juvenile Atlantic nurse sharks (Ginglymostoma cirratum) grow more rapidly as juveniles and reach smaller maximum sizes than nurse sharks in Bimini, Bahamas—locations so close that these populations have historically been assumed to be the same.
Evidence from long-term fisheries-independent monitoring by the Shark Research and Conservation Program at the Rosenstiel School shows Biscayne Bay is an important nursery habitat for numerous species of shark.
"Despite human degradation of Biscayne Bay, our data suggests it remains critical habitat for many species of juvenile shark, providing essential resources and protection from predation early in life," said John Hlavin, Ph.D. student in the Abess Center for Ecosystem Science and Policy and lead author on the study.
"Using data from nurse sharks captured more than once between 2017 and 2025, we were able to assess their growth rates and estimate the size of habitats they rely on based on the distance between initial and final capture," said Emily Yeager, co-author of the study and a doctoral candidate in the Department of Environmental Science and Policy at the Rosenstiel School. "We found significant differences that show more rapid growth at smaller sizes in Biscayne Bay compared to the Bahamas."
The study found that juvenile nurse sharks in Biscayne Bay likely rely on small home ranges while young, which increase in size as they grow, and that their growth rates and maximum size are distinct from nearby nurse sharks in the Bahamas.
"These differences are likely to be driven by variances in access to resources, suggesting that resource availability may be more limited in Bimini, or that juveniles in Bimini may face greater competition from abundant juvenile lemon sharks that share those habitats," said Catherine Macdonald , Ph.D., an associate professor in the Department of Environmental Science and Policy, and the director of the Shark Research and Conservation Program. "These groups may show these significant differences as a result of greater resource availability and/or historic fishing pressure, which has been shown to select for faster growth and smaller maximum sizes."
Because South Florida includes extensive recreational fisheries and a historic fishery targeting nurse sharks for their skin and liver oil, there may be genetic differences in nurse shark populations in Florida that explain the observed differences.
The authors emphasize the importance of long-term monitoring that can provide these kinds of data sets.
"Conducting studies of life-history traits across different habitats within a region can help us better understand how local variation might affect traits that are essential for science-based fisheries management," added Hlavin. This is especially important for species like nurse sharks that are threatened by poorly managed or unmanaged fisheries in many parts of their range."
The research was supported by the University of Miami's Abess Center Fellowship, Florida Sea Grant–Guy Harvey Foundation, and the National Science Foundation Graduate Research Fellowship
The study, titled "Is the seagrass greener on the other side? Faster growth in Biscayne Bay, Florida's nurse sharks (Ginglymostoma cirratum) compared to neighboring conspecifics of Bimini, The Bahamas" was published in the journal Environmental Biology of Fishes on December 18, 2025. The authors include John Hlavin*1,2,3,4, Emily Yeager1,2,3,4, Christine Martin1,2,3,4, Christopher Will1,2, Nicholas Perni2, Christian Pankow1,2, and Catherine Macdonald1,2,3
¹ Shark Research and Conservation Program, University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, ² Field School Scientific Training, ³ Department of Environmental Science and Policy, University of Miami, ⁴ Abess Center for Ecosystem Science and Policy, University of Miami
About the University of Miami and Rosenstiel School of Marine, Atmospheric and Earth Science
The University of Miami is a private research university and academic health system with a distinct geographic capacity to connect institutions, individuals, and ideas across the hemisphere and around the world. The University's vibrant academic community comprises 12 schools and colleges serving more than 19,000 undergraduate and graduate students in more than 180 majors and programs. Located within one of the most dynamic and multicultural cities in the world, the University is building new bridges across geographic, cultural, and intellectual borders, bringing a passion for scholarly excellence, a spirit of innovation, and a commitment to tackling the challenges facing our world. The University of Miami is a member of the prestigious Association of American Universities (AAU).
Founded in 1943, the Rosenstiel School of Marine, Atmospheric, and Earth Science is one of the world's premier research institutions in the continental United States. The School's basic and applied research programs seek to improve understanding and prediction of Earth's geological, oceanic, and atmospheric systems by focusing on four key pillars:
*Saving lives through better forecasting of extreme weather and seismic events.
*Feeding the world by developing sustainable wild fisheries and aquaculture programs.
*Unlocking ocean secrets through research on climate, weather, energy and medicine.
*Preserving marine species, including endangered sharks and other fish, as well as protecting and restoring threatened coral reefs. www.earth.miami.edu .
