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North Carolina's Shark Diving
Shark Biology 101
The Sand Tiger Shark (Carcharius taurus) is known as the Ragged Tooth Shark or Grey Nurse Shark in other parts of the world. A live bearer, the waters off the coast of North Carolina are thought to be this shark's breeding grounds. The fresh wounds seen on females as a result of the Sand Tiger's mating ritual, lends credence to this theory.
The most common reproductive method among sharks involves internal egg laying with gestation and live birth. Scientifically referred to as ovoviviparity, Sand Tigers have a unique variation of this process known as intrauterine cannibalism. The first unborn shark in each of the mother's two oviducts that reaches about 55 mm in length swims to the uterus where it feeds upon the embryos of its siblings and other infertile eggs. Typically each mother will produce two pups, each about three feet in length.
Sand tigers normally obtain a maximum length of about 11 feet in the Atlantic. On occasion a larger specimen is spotted. They are grey–brown on their upper bodies and light grey or white on their undersides. This counter shading helps to make them difficult to see when viewed from either above or below. They have two dorsal fins of approximately the same length and a pointed nose. The upper portion of their tail fin is substantially longer than the lower lobe. They frequently swim with their mouths slightly open giving a clear view of their three rows of fang like teeth. These teeth are shed and replaced about every two weeks providing a popular souvenir for divers.
Like humans, the Sand Tigers have sense of touch, smell, hearing, sight and taste. Unlike people these sharks also have a sixth sense called electroreception. Pores on the bottom of the shark's snout allows them to detect very weak electrical signals. This sense is used to help them detect prey, particularly in murky water, and to use the Earth's magnetic field for navigation.
Sand Tigers are considered sluggish sharks. They feed on small, slow boney fishes, bottom dwellers and crabs. Unlike the "super sharks," such as the Great White or Tiger shark, their small teeth are not suitable for tearing flesh from larger prey.
Lacking a swim bladder, the Sand Tiger shark's have large, oily livers. As the shark's liver oil is much lighter than seawater it helps to provide buoyancy. The shark's pectoral fins provides lift as it swims. Sand Tigers are known to swim to the surface, taking large gulps of air to aid with buoyancy. Unlike many other species of shark, they are frequently seen hovering motionless along the bottom.
Sand Tigers have a shorter glide path, or swimming pattern, than most other shark species. This characteristic, combined with their docile nature, ease of capture and the fierce appearance of their ragged teeth, makes them a popular species for display in public aquaria.
Sand Tiger sharks tend to congregate in large numbers at several of the shipwrecks off North Carolina's coast. Because of this there is no need for baiting or feeding to generate an artificial shark encounter for divers. Many divers find this a more pleasing and natural experience than the staged shark dives offered at other popular dive destinations.
Despite the fierce appearance given the Sand Tiger by its toothy smile, these sharks are quite docile. Aggressive displays towards divers are very rare. On the unusual occasions that problems have occurred it usually involved a diver cornering a shark in a piece of wreckage or a diver touching or grabbing one of the sharks. Sand Tigers have also been known to take a spearfisherman's catch.
While Sand Tigers don't seem to mind the presence of divers they can be difficult to approach. Being curious in nature, however, they will often approach a diver that is kneeling on the bottom. Sand Tigers have been known to swim between the legs of divers standing on the bottom and will frequently approach stationary divers within an arms length.
The largest concentration of Sand Tigers isn't always directly on the shipwreck. Often times large numbers of these graceful creatures will be found several feet off the side of the a wreck, out in the sand. By swimming near the edge of the visibility range, keeping the wreck in sight to insure a safe return, or exploring off the side of a wreck using a line reel divers may find dozens of sharks lined up in rows like cars in a parking lot.
While Sand Tigers are the most commonly encountered shark along the Carolina coast it is not unusual to spot other species mixed in with them. By keeping a sharp eye divers may also see an occasional Sand Bar, Thresher or Nurse shark mixed in with the Sand Tigers. Divers exploring North Carolina waters are also sometimes treated to sightings of Scalloped Hammer Head, Bull and Dusky sharks. Though very rare a variety of other species are also seen from time to time.
For several years the wreck of the "Papoose" was the area's best known and most popular site for shark diving. Because of its proximity to the Gulf Stream visibility of 100 feet or more is not unusual at this site during the summer months. Resting in about 120 feet of water, it was common for this wreck to be loaded up with sharks as far as the eye could see. Sank by the U-124 during World War II, this large oil tanker provides a world class wreck dive, with or without the presence of sharks. Since the end of the 1999 hurricane season Sand Tiger shark encounters at this site have been infrequent.
Another World War II casualty, the wreckage of the tanker "Atlas" is a hot spot for Sand Tiger shark encounters. This partially intact shipwreck sits upright in about 125 feet of water. Portions of this large wreck reach within 90 feet of the surface. Sank April 9, 1942 by the U-552, there is almost always a large population of Sand Tigers at this site. Since the "Atlas" rests close to Cape Lookout Shoals, visibility at this site is typically restricted to around 60 feet.
Torpedoed March 11, 1942 by the U-158, the "Caribesea" is one of the area's most popular sites for shark encounters. With a maximum depth of 90 feet to the sand, and much of the wreck 10 to 20 feet shallower, this site provides divers with longer bottom times than many of the other popular shark diving locations. The bow section used to reach within about 45 feet of the surface but is starting to fall in on itself providing less relief now. While the bow area looks tempting for penetration, the structure has become quite unstable recently. Divers should resist the urge to go inside. The "Caribesea" has held a large congregation of Sand Tigers for several years.
Part of North Carolina's artificial reef program, the "Aeolus" has recently been providing a home for a few Sand Tigers. This 409 foot long transatlantic cable layer originally rested intact on its starboard side. The hurricanes of 1996 ravaged the site, breaking the monstrous ship into three distinct sections and turning part of the wreckage upright. Today the site has the appearance of a natural shipwreck and provides plenty of opportunity for penetration. Because of its large size, divers are advised to limit their explorations to the section of the wreck their charter boat is tied in to. While Sand Tigers aren't seen in the numbers or frequency they are on some other sites, this is a popular location for a second dive and does provide an occasional shark encounter.
Several other shipwrecks resting on or near Cape Lookout Shoals attract large populations of Sand Tiger sharks. However, due to their location, visibility at these sites is frequently less than 15 feet. Since many divers find encounters with large predators in such low visibility conditions somewhat unnerving, these sites are visited infrequently by local charter operators.
Shark diving isn't restricted to the sites visited by Morehead City area dive operators. To the north, charters running out of Hatteras and Ocracoke can provide patrons with Sand Tiger shark encounters. To the south of North Carolina's Crystal Coast sites with Sand Tigers can be dived out of Wilmington and Southport.
North Carolina's large Sand Tiger shark population provides divers with the rare opportunity to dive with apex predators without the need for baiting. With its unique snaggle-toothed grin, graceful movement and classic streamlined body, the Sand Tiger shark is a joy to view, photograph or video tape. The absence of feeding results in an environmentally sound shark diving experience with minimal impact on the ecosystem. Because of their docile temperament and the lack of an artificially produced feeding frenzy, these encounters are relatively safe. By applying a little common sense, resisting the urge to touch the animals, leaving an open exit path when encountering sharks inside a shipwreck and not taking game in their presence, the risk of a shark bite is virtually eliminated. Without dispute, Sand Tiger sharks provide divers with one of North America's best underwater adventures.
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