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Introduction to How Angel Sharks Work

Are angel sharks the holiest fish in the sea? Their name certainly seems to indicate a pure and pious air, and some seafood connoisseurs say that a bite of an angel shark is like a little taste of heaven. Or did they get the name because it's a miracle that they're classified as a shark at all? After all, angel sharks certainly don't resemble the typical shark, which has a torpedo-shaped body and ominous fins that warn of its presence. Instead, the angel shark looks like it has been run over by a car or flattened by a very big iron.

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The angel shark more closely resembles a skate or a ray, the bottom-dwelling cousins of the shark, but it's classified as a shark in the family Squatinidae, which has one genus: squatina. Squatina is Latin for "a kind of shark," perhaps reflecting early confusion about just what kind of shark this was. But certainly the name sounds right -- these sharks are stocky and shorter than other sharks.

But what about their other name, angel shark? Squatina's 19 species of angel sharks get their name from this atypical appearance. The flaps around their head are actually flattened pectoral fins, which gives them the look of a shark with wings or a halo, like an angel. Or perhaps if you see the hood of a monk's habit, you might call them by their other name, monkfish. While those flattened pectoral wings provide their devout moniker, they also represent the divine intervention that kept these angels classified as sharks. Whereas skates' and rays' pectoral fins are attached to their head, the angel sharks' fins are not. This difference may be small, but it keeps these creatures in the shark family.

These flattened fins also allow them to spend a lot of time lying on the bottom of the ocean floor, waiting for a meal to swim by. But even if they're not as ferocious-looking as other sharks, don't underestimate them. Their sharp teeth and tenacious bite have earned them a nickname on the other end of the religious spectrum: sand devil.

We don't have to go all the way to heaven to get to know the angel shark a little bit better. We only have to go as far as the next page, where we'll take a further look at the angel shark's cherubic anatomy.

The anatomy of an angel shark

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Angel Shark Anatomy

As we mentioned, the angel sharks live up to their "squatty" name, with most species of squatina measuring only about 5 feet (1.5 meters). A few species, such as the Japanese angel shark and the Mediterranean angel shark, may be as long as 6.5 feet (2 meters), but that's about as long as they get. While most weigh about 60 pounds (27 kilograms), the biggest angel shark, found in Europe, has been known to weigh 170 pounds (77 kilograms) [source: Lineaweaver].

Angel sharks look more like rays than great whites, but they have all the same basic equipment as sharks. It just happens that the equipment is flattened dorsoventrally, or from top to bottom. The pectoral fins that give the angel shark its name are probably the first thing to strike your eye. To review, these fins aren't attached to the head, as they are in rays. The pelvic fins are similarly flattened and expand outward from the body.

The mouth is located at the very tip of the snout, and inside are some truly scary teeth. Shaped like triangles, the teeth are extremely sharp and come to needlelike points. On either side of the mouth are barbels, which are whiskerlike antennae that sniff out the chemical reactions of prey along the bottom of the ocean floor.

Along the side of the head are gill slits that allow the angel shark to breathe. The positioning of the gill slits represents another important distinction from rays and skates, which have gill slits on the bottom of their heads. Unlike many other sharks that must constantly swim to pull water over their gill slits, the angel shark uses its muscles to pull water over the gill slits while in a resting position. This shark also has a spiracle, or a tube behind the eyes that can pull in water when the shark's mouth is closed.

One way that angel sharks do differ from other sharks is their caudal fin, or tail. Most sharks' tails are top-heavy, meaning that the top lobe of the fin is bigger than the second one. The opposite holds true for angel sharks. They have a longer lower lobe, which may help them achieve a quick liftoff when they attack their prey from below.

A successful attack from below is the key to an angel shark's next meal. Many of the angel shark's features, from its flattened body to its barbels to a tail that helps it move upward quickly, allow it to live at the bottom of the ocean floor, waiting for prey to swim by. Even its coloring provides camouflage. Angel sharks are various shades of white, gray, brown and black, colors that blend in with the ocean floor. Some have red spotting, which may provide even more coordination with their habitat.

Find out where they're lying in wait, and what exactly they're waiting for, on the next page.

The angel shark buried at the bottom of the ocean floor

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Angel Shark Habitat and Hunting

Angel sharks are found all over the world, including both the western and eastern sides of the Atlantic and Pacific oceans [source: Compagno]. They're generally not found in the Indian Ocean, except for one southwestern corner. To learn exactly where angel sharks are found, see the sidebar.

Of all the angel sharks, the Pacific angel shark is probably the most studied and best known, although many of these species are likely the same except for location. Even if they make their homes in different parts of the world, in waters ranging from cool to tropical, angel sharks are still seeking out the same parts of the ocean. They're found on the very bottom of the ocean floor, either in shallow areas or at depths of up to 4,265 feet (1,300 meters).

The angel shark buries itself into the sand and mud at the bottom of the ocean floor, with only its eyes poking out. They can lie there for days at a time, waiting for the perfect meal to swim by. When this shark strikes its prey -- normally fish, such as flounder and halibut, crustaceans or mollusks -- its front half rises suddenly to ambush the prey from below. It can attack and capture its prey in a tenth of a second [source: Martin]. Angel sharks seem to favor one hunting spot strongly, but if the local fish figure out where the shark is hiding, then the angel shark will temporarily move several miles away.

While their barbels are constantly working, the most important sense to a hunting angel shark is its sense of sight. In a study, Pacific angel sharks were presented with rubber fish, which didn't contain any of the same olfactory, electrical or vibratory cues of a regular fish. The angel shark struck at virtually all of the targets [source: Martin]. When hunting at night, angel sharks are tipped off to a fish's presence by the bioluminescent plankton in the fish's wake. Some angel sharks are probably exclusively nocturnal.

When provoked, the angel shark turns its sharp bite on humans, but generally, angel sharks have much more to fear in terms of us taking a big bite out of them. Find out about angel shark fishing on the next page.

Does this look appetizing to you?

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Angel Shark Fishing and Recovery

Larger sharks, including the great white shark, may prey on the angel shark, but the angel shark's real threat is man. Or more specifically, one man, by the name of Michael Wagner. Until the 1970s, angel sharks were thought of as a "junk fish," something that got caught in a fishermen's net by accident. Fishermen threw them back, until Wagner, a seafood processor in California, began to spread the word about the tastiness of the Pacific angel shark.

Wagner's campaign was almost single-handedly responsible for bringing the angel shark to millions of plates. In 1977, only about 366 pounds (166 kilograms) of Pacific angel shark were caught, but by 1984, that had become 700,000 pounds (317,545 kilograms) [source: Monterey Bay Aquarium]. When fishing for this shark reached its peak in 1985 and 1986, about 1.2 million pounds (544,311 kilograms) of sharks were being caught each year [source: Martin].

While this was good news for inventive cooks and shark connoisseurs, it was extremely bad news for angel shark populations, which were nearly decimated when the high fishing rate was combined with their low reproductive rate and slow growth.

Pacific angel sharks typically give birth to litters of about 8 to 13, while other species may have litters of just six or up to 25 [sources: Martin, Awruch et al., Hansen]. The gestation period varies among species but is generally between eight and 10 months. Angel sharks are ovoviviparous, which means that the females carries the eggs, but the eggs hatch inside and the pups are born live. Angel shark pups measure only about 9 inches (23 centimeters) at birth. Adults try to protect the small pups by giving birth in deeper waters [source: Martin]. Still, only about 20 percent of Pacific angel sharks survive to maturity [source: Bester].

Not every angel shark is subject to this kind of fishing, but many angel shark populations have been declining [source: Morey et al.]. In some areas, the fish appears to have vanished completely, but specific numbers are hard to come by. These sharks are listed as "vulnerable" by the International Union for Conservation of Nature (IUCN), and some of the fisheries are subject to increased regulation. When not caught, it's estimated that angel sharks live about 25 years [source: Kay].

You can fish for more information on angel sharks and other shark species on the next page.

Lots More Information

Sources

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  • Bester, Cathleen. "Pacific Angel Shark." Florida Museum of Natural History Ichthyology Department. (May 19, 2008) http://www.flmnh.ufl.edu/fish/gallery/descript/pacificangelshark/ pacificangelshark.html
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