Shark Nurseries

When a person thinks of Florida’s estuaries, it usually conjures images of schools of brightly colored fish, wading birds in great numbers and scores of blue and stone crabs. However, sharks are also prevalent in the state’s estuaries and are the top predators within these waters. They use the protected estuaries as nurseries for their young, which provide an abundance of food and protection from predators, such as larger sharks.

To learn more about these amazing animals, Florida Department of Environmental Protection biologists at Rookery Bay National Estuarine Research Reserve have been studying sharks to see how their habitat is affected by water quality conditions.

The shark study is taking place among the Ten Thousand Islands portion of the Rookery Bay Reserve off the coast of Naples. Sharks are captured around sunset, when they are most active, using a monofilament gill net and baited long lines. Once in the boat, each shark is weighed, measured, tagged and released. Water conditions, including temperature and salinity, are documented. The variety of shark species found in an estuary gives scientists clues regarding salinity levels, or how much salt is present in the water. Bull sharks (Carcharinus leucas) are the dominant species caught in Faka Union Bay, one of three bays in the study area. Bull sharks are more tolerant of low salinities than other sharks, and freely move from marine to freshwater locations. Other types of sharks documented in the study include bonnethead, lemon and blacktip.

Scientists hope to learn more about sharks by documenting the different types found in each location to determine how they react to changes in their environment. Research results are used by many entities including the partners in Everglades restoration.

“By monitoring salinity trends in these estuaries and examining the water quality in the areas that sharks prefer, we can help guide South Florida Ecosystem restoration efforts with the results of this research to ensure healthy habitats for all marine life,” said Reserve manager Gary Lytton.

For more information, please visit: www.rookerybay.org.