Sharks and Rays
Sharks, rays, and skates all belong to the category of cartilaginous fish. These jawed fish are distinguished by their skeletons, which are made of cartilage rather than bone.
The Gulf of Mexico is home to more than a dozen different species of sharks. Many species are apex predators, at the very top of the food chain. Sharks are well known for their many rows of razor sharp teeth. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward, much like a conveyor belt; some sharks lose 30,000 or more teeth in their lifetime. Sharks have a keen sense of smell, with some species able to detect as little as one part per million of blood in seawater. Like humans, sharks can contract and dilate their pupils, allowing them to see well in both light and dark waters. While many people fear sharks, shark attacks on humans are extremely rare.
Sharks that live in the Gulf of Mexico include the bull, thresher, nurse, hammerhead, oceanic white tip, blacktip, sandbar, shortfin mako, blacknose, and finetooth.
Several species of ray also make their homes in the Gulf. Most rays have flat, disc-shaped bodies and broad, wing-like fins with gills underneath. Many possess unique adaptations, such as a venomous barb on their tail or the ability to produce an electric discharge. Rays and ray-like fishes in the Gulf include the manta ray, southern stingray, smalltooth sawfish, and Atlantic Guitarfish.
Types of Sharks
Bull sharks are gray with an off-white underside. They have a blunt nose, stout body, and no dorsal ridge. They are slow swimmers, can breathe while at rest, and grow to about ten feet. They are the only sharks that are just as happy in fresh water as salt water and have been found as far as 2,000 miles inland. Bull Sharks are world-class travelers and have been sighted in Lake Nicaragua, Guatemala's Lake Yzabal, the Spanish Main, and New York, but their favorite hangouts are in shallow waters along the continental shelves. They aren't picky eaters—they'll eat just about any kind of fish.
Thresher sharks reach a length of 13 to 20 feet, with a tailfin nearly as long as the rest of their body. They love the warm tropical and sub-tropical waters out in the open Atlantic and Pacific oceans, often feeding in groups on schools of small fish. They use their long upper tail fin to stun small fish.
Nurse sharks have both dorsal fins set far back. They have small eyes and a big nose with fleshy barbs hanging off them that can detect prey hidden from view. This compensates for the nurse shark's poor eyesight. Nurse sharks have conical teeth used for crushing the shells of crabs and mollusks. They replace a row of teeth about every two weeks during warm weather. By the time nurse sharks reach nine feet, they turn grayish or yellowish-brown all over. They live on the bottom of shallow waters in the Western Atlantic as far north as Rhode Island and as far south as Brazil.
Hammerhead sharks can be found both offshore and inshore, even entering shallow bays. They are well known for their distinctly flat heads, the shape of which is known as a cephalofoil. The positioning of their eyes allows them to see in almost 360 degrees, meaning they can simultaneously see above and below themselves. Hammerheads eat fish and stingrays.
Oceanic White Tip Shark
Oceanic white tip sharks are open-sea sharks very rarely seen close to land. Unlike most sharks, white tips have been known to be aggressive towards humans. Their Latin name means "long hands" because of their long pectoral fins. They are primarily solitary but are reported to feed in groups when a food source is present.
Blacktip sharks are found in shallow water and form an important part of the commercial shark catch in Florida. They are smooth-backed, lacking a ridge. The tips of the dorsal, pectoral, rear, and lower caudal fin are all black, giving the shark its name. Size at maturity is between 5.5 and 6.5 feet, and they frequently swim in schools.
Sandbar sharks are also known as brown sharks. They're medium-sized sharks with a large first dorsal fin that's placed far forward, a much smaller second dorsal, and a ridged back. Sandbar sharks love the warm waters in southern Florida but will travel all the way to the shallow bays of Long Island Sound to give birth to their young.
Shortfin Mako Shark
The shortfin mako shark has big pointy teeth but rarely chews its food thoroughly. Once an unlucky tuna or mackerel gets nabbed, the mako shark swallows it whole. It also likes to hunt along the ocean floor. The shortfin mako is one of the better-looking shark species. It is a beautiful blue on top and pure white underneath. An adult is usually about 12 feet long.
The blacknose shark matures at 3.5 to 4.5 feet. It has a long snout with a dark spot and asymmetrical upper teeth. Its color can be cream to yellowish-gray above, and a paler shade of the same or white below. This kind of color differentiation is typical of almost all sharks that frequent the upper layers of the ocean and is effective camouflage against the deeper water or bottom when viewed from above and against the light when seen from below.
The finetooth shark is a small, slender, inshore shark species. It is recognizable by a very long second dorsal fin that is much smaller than the first dorsal.