Virginia Key, Fl.— Biscayne Bay has been designated an Important Shark and Ray Area recognizing the heavily urbanized estuary as an essential habitat for nine shark and two ray species, including threatened and endangered species.
The designation is supported by 10 years of research led by the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science. The findings show that the bay provides nursery and reproductive habitat for species ranging from bonnetheads and nurse sharks to great hammerheads and tiger sharks. It also serves as an important feeding area for three species and contains aggregations of lemon sharks that researchers are continuing to study.
Important Shark and Ray Areas, known as ISRAs, are scientifically identified areas that play a significant role in the development and survival of sharks, rays and chimaeras. ISRAs identify areas that are important to shark and ray reproduction, including gestation, mating, and pupping, that are essential for newborn sharks in their first year of life, or that are disproportionately important for shark feeding, resting, movement, or aggregations. The initiative was developed by the International Union for Conservation of Nature Species Survival Commission Shark Specialist Group to help ensure that critical habitats are considered in conservation, marine planning and environmental decision-making.
"Biscayne Bay is often discussed in terms of environmental decline, but that is only part of its story," said Catherine Macdonald, an associate professor in the Department of Environmental Science and Policy at the Rosenstiel School and the Robert K. Johnson Center for Marine Conservation, who led the designation effort. "The bay continues to function as an extraordinarily important habitat for sharks and rays, including species of conservation concern. Its ecological value needs to be part of ongoing decisions about Biscayne Bay's future."
The bay's shallow waters, which average about 6 feet deep, offer young sharks some protection from larger predators. It's a warm, food-rich environment which also supports gestating females and the growth of juveniles. Researchers documented an unusually high concentration of young sharks from several species, making Biscayne Bay a rare example of a productive shark nursery alongside a major metropolitan area.
Macdonald and her team began collecting data on sharks and rays in 2016 using drumlines, longlines, baited underwater video stations, drone surveys and shore-based rod-and-reel fishing. The effort represents thousands of hours of fieldwork and contributions from more than 100 University of Miami undergraduate and graduate students and collaborations with peer institutions.
Macdonald estimates 10,000 people have participated in the broader research and education effort, including schoolchildren, community members and citizen scientists. Between 800 and 1,000 South Florida students take part in Rosenstiel School's Shark Research and Conservation Program's (SRC) shark-tagging activities each year.
"Long-term research gives us the evidence needed to identify habitats that are important to wildlife and people, document changes over time, and make meaningful contributions to conservation," Macdonald said, who is also the director of the SRC at the Rosenstiel School. "This designation reflects the work of the many students, researchers and community participants who have helped us build a detailed picture of how sharks and rays use Biscayne Bay."
Supporting research has found that juvenile nurse sharks in Biscayne Bay grow faster than those studied near Bimini in the Bahamas. The team has also examined genetic differences between bonnetheads in Biscayne Bay and Tampa Bay and collected reproductive information about bonnetheads in a recent study.
The designation comes as warming waters, declining water quality and coastal development create new concerns for species that rely on South Florida's estuaries. These waters are warming an estimated 6.9 times faster than the global ocean average. Researchers have already begun connecting unusually warm years with changes in the body condition and parasite loads of juvenile sharks.
An ISRA designation does not establish a marine protected area or impose new legal restrictions. Instead, it provides scientific evidence that can inform fisheries management, environmental impact assessments, habitat conservation, marine spatial planning and infrastructure decisions. It may also help ensure that the importance of shark and ray habitat is considered in federal, state and local planning processes and international conservation commitments.
"The designation provides decision-makers a stronger scientific basis for considering sharks and rays when evaluating activities that could affect the bay's water quality and habitat," Macdonald said. "Biscayne Bay is not ecologically barren. It remains a productive ecosystem that supports marine life at critical stages of development."
The Biscayne Bay designation also demonstrates how long-term, independent monitoring programs can produce data with direct conservation value. Researchers plan to continue studying how sharks and rays use the bay and how environmental changes may affect their health, reproduction and survival.
