If you want to see a shark in the South Florida national parks, you go to Shark Valley or Shark River Slough in Everglades National Park, right?
Both areas are predominantly freshwater ecosystems. The name "shark" was given to them as a result of alleged sightings of meandering sharks where the famed River of Grass meets the coast.
So, where are the sharks in our South Florida national parks?
They can be found offshore and along the coast of the Ten Thousand Islands and Florida Bay in the Everglades, in the bay and offshore in Biscayne National Park and in the waters surrounding Dry Tortugas National Park. Sharks also can be found in the waters all around the Florida Keys and throughout the Caribbean.
What kind of sharks are you going to find?
Neil Hammerschlag, director of the Predator Ecology Lab and Shark Research and Conservation Program at the University of Miami, says the most common sharks in Florida Bay and Biscayne Bay are lemon, bonnetheads, great hammerhead, nurse, bull, blacktip, tiger and Atlantic sharpnose.
George Burgess, director of the University of Florida's Florida Program for Shark Research, notes that there also are scalloped hammerheads, blacknose, Caribbean reef and sandbar sharksin waters adjacent to the Ten Thousand Islands, Biscayne Bay, Florida Keys and Dry Tortugas. He added that shortfin and longfin mako sharks and silky sharks ply deeper "blue waters. "The great white shark, a winter visitor to these waters, is the inspiration for the movie "Jaws."
"On any given day, we can tag up to 10 species of shark in South Florida," Hammerschlag said. "Florida has one of the highest diversities of sharks in the world. You're likely to find more shark species only in Indonesia and a few other places."
In addition to sharks, rays and skates are also members of the elasmobranch class. One of the major features that they share is a cartilaginous skeleton. Rays have been described as being a kind of "flattened" shark. Most scientists agree they should be studied together, as related species.
Rays and skates can be found basically where there are sharks. Burgess focuses his research on sharks and rays that can be found in Florida Bay and areas to the south. Rays include the endangered smalltooth sawfish, southern, bluntnose, roughtail, yellow stingrays, Atlantic cownose, spotted eaglerays and smooth and spiny butterfly rays.
The life cycle of a shark or ray is not well-known because of the difficulties in tracking their movements. Great hammerheads may be the longest-lived of common sharks. Some have been estimated to be 40 years old. Great whites may live up to 70 years. Most species are estimated to live up to 30 years, and rays can live up to 15 to 25 years in the wild.
A trait of all sharks and rays is that they reproduce late in life. Many sharks mature well into their teen years, and most rays do not mature until they are about 10. Male great white sharks may not mature until they are 26 to 33.Their late maturity makes shark species more susceptible to the pressures that reduce their population.
"Sharks are the 'canary in coal mine' of the marine environment," Hammerschlag said. "You can think of them as being at the top of a health system made of building blocks, like Jenga. Sharks need a lot of food below them in the food chain to have a sustainable population."
Many of the shark and ray species stay in South Florida waters throughout their lives. Newborn and juvenile sharks and the smalltooth sawfish find refuge in the shallow, tangled mangrove forests of Shark River Slough and in the Ten Thousand Islands. Because many other fish also use these areas as nurseries, there can be plenty of food there for the growing "toothy" predators.
Hammerschlag says that there are signs that the tiger and lemon shark populations are not as robust as they once were, and individuals do not seem to be as large as they were a few years ago. He points out that a critical piece of information about what we don't know about sharks in South Florida is how well they are doing. Current research is helping scientists learn more.
Most sharks and many of the rays are highly migratory, often seen following such migrating fishes as tarpon, jacks and herrings. Satellite tagging has allowed researchers at NOAA and many universities to track and study migrating shark populations.
Recent research at the Shark Research and Conservation Program is looking at the structure of the mangrove and coral reef food web and how it is affected by climate change. Researchers are finding that where corals are bleached, the reef fish populations are declining and that this is leading to the decline in the number of shark observations.
Scientists at the Florida Program for Shark Research, in collaboration with NOAA, Florida State University and the Florida Wildlife Conservation Commission, are studying the life cycle of smalltooth sawfish, also known as the carpenter shark, in Everglades National Park and the Florida Keys.
"The story of these animals is that the park boundaries largely coincide with where the remnant population of sawfish is found," Burgess says. "Getting them back on their feet here will determine the recovery of the rest of the U.S. population."
The only federally endangered marine fish in South Florida waters is the smalltooth sawfish. Some of the sharks, skates, and rays that can be found in South Florida's national parks are listed as endangered, near-threatened or vulnerable by the International Union for Conservation of Nature and Natural Resources (IUCN) on their Red List of Threatened Species (http://www.iucnredlist.org/). This list is important for the protection of marine animals because a large percentage of the Earth is affected by changes in the biodiversity of coastal and marine habitats.
More is being learned about sharks everyday. The more we learn, the more we can do to protect and appreciate them as an important part of our marine and coastal ecosystem.