2017-08-01 / Features

I've got friends in wet places...

MEET SOME CARCHARHINIDAE, better known as sharks
By Escambia County Marine Resources manager Robert Turpin

Robert Turpin Robert Turpin

More than a dozen species of the “requiem” shark family Carcharhinidae may occur in the brackish and salt waters around Escambia County. Bull sharks have been observed within fresh water rivers. Other sharks are listed in my personal encounter story about sharks in this edition of Splash! All sharks are capable of injuring humans. Sharks have teeth that are also known as “dermal denticles” on their skin.

They are ancient creatures with cartilaginous skeletons. Their teeth and skin dermal denticles are their hardest features. They lack swim bladders, but compensate with a large oily liver to provide some buoyancy. All sharks have at least one dorsal fin. Dogfishes, lemon and nurse sharks have two dorsal fins. Some species, such as deepwater sharks, may live more than 100 years. Maximum lifespans are unknown for many shark species. Most local species probably live 20-50 years.

Some local species grow to only 2-3 feet. Bull, mako and hammerhead sharks have maximum known lengths of 10, 15 and 18 feet, respectively. Depending upon species, the newborn length of most local species ranges between a few inches and a few feet. Sharks’ reproductive strategies are different than most marine fishes. Most sharks give birth to live young. The longer gestational period of sharks allows the offspring to be larger and more mature. This improves offspring survival rate and allows the female shark to give birth in a specific “nursery”’ habitat.

However, the trade-off to this reproductive strategy is the limited number of offspring produced by female sharks. The brood size of most local shark species is fewer than 50. The species with the most limited known brood size is grey nurse shark, Carcharius taurus. Gray nurse shark females have two ovary chambers in which the oldest/biggest/strongest embryonic shark in each chamber eats all of the other eggs and embryos. Thus, only two pups are produced by each female during each reproductive cycle. Another feature of the shark’s reproductive life cycle is the late age of reproductive maturity. Female sharks of some species become reproductive at ages up to 20 years or more. The combination of late reproductive maturity and low reproductive rate make some shark species vulnerable to over-fishing.

Most local sharks are regulated by Florida and federal fishing restrictions. Some species, such as the Great White, are protected. Sharks are not known for being maternal/paternal creatures. Neither parent has been observed raising offspring in any shark species. Most sharks feed on fish, squid, crustaceans and such. Some feed only on live prey, and some species feed only on carcasses. Nurse sharks sometimes feed on mollusks, such as conchs. Tiger sharks apparently eat anything, including inanimate objects.

Tiger shark teeth are shaped in such a way that allows them to prey on sea turtles. Some sharks, for example, dogfishes, Atlantic sharpnose sharks and others, are commonly found very close to shore. Most other species may be seen swimming very close to shore.

Florida Fish and Wildlife Conservation Commission and National Marine Fisheries Service regulate sharks in Florida and federal waters. Sharks can be seen virtually anywhere in waters connected to the Gulf of Mexico. Some of the best locations to see sharks are local piers.

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