Shark FAQs

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Nurse shark's mouth

Shark meat is palatable and nutritious if properly prepared. In some countries shark meat is marketed under its common name, in others it is marketed under various names. The fish in England's "fish & chips" is sometimes dogfish or school shark, although this would be considered low quality fish & chips. True fish & chips consists of cod or haddock (the 2 most popular) and also plaice. The prejudice against shark meat arises from a distaste for the scavenging habits people attribute to sharks, and to the fact that the meat spoils quickly. The meat of certain species is apt to be strongly flavored, a characteristic that may be reduced by icing for 24 hours, then soaking for two hours in brine Dry salted shark has become a staple food in some countries where salt cod was formerly popular. But shark liver should never be eaten; its high concentrations of vitamins can cause illness in humans.

It is only a rumor that the hammerhead is poisonous.

Blue shark

In life the blue shark displays a brilliant blue color on the upper portion of its body and is normally snowy white beneath. The blue quickly fades to dull grey after the shark is killed. The mako and porbeagle sharks also exhibit a blue coloration, but it is not nearly as brilliant as that of a blue shark. In life most sharks are brown, olive, or grayish.

Considerable research has been devoted to finding out what stimuli attract sharks and incite them to attack. Results are mostly inconclusive, but some general principles have been advanced: Certain types of irregular sounds - like those made by a swimmer in trouble or a damaged fish - seem to attract sharks from great distances. Sound, rather than sight or smell, seems to be a shark's primary cue for moving into an area. Some scientific experiments indicate that sharks can distinguish light colors from dark, and that they may even be able to distinguish colors.

Yellow, white, and silver seem to attract sharks. Many divers maintain that clothing, fins, and tanks should be painted in dull colors to avoid shark attacks. Though blood itself may not attract sharks, its presence in combination with other unusual factors will excite the animals and make them more prone to attack.

Great white shark

The most dangerous species in order of documented attack records are: the great white shark, bull shark, tiger shark, grey nurse shark, lemon shark, blue shark, sand tiger, several species of hammerheads, and the mako. Some species such as the nurse shark are extremely sluggish and have poorly developed teeth, but even these have been known to attack man when excited or disturbed.

The barracuda (though divers claim its ferocious reputation is undeserved), moray eels, octopuses, and sharp-spined sea urchins can be dangerous to swimmers. The Portuguese man-of-war has tentacles up to 50 feet long with specialized cells that produce painful stings and welts on contact by swimmers.

Sting rays, toadfish, catfish, and jellyfish can inflict damage on swimmers and waders. Certain coral-reef organisms are to be avoided by divers.

Sharks do not have bones. Sharks are made up of cartilage, and are called Elasmobranchs, which translates into fish made of catilaginous tissues. Even though they don't have bones they still can fossilize.

Shark skeletal systems are composed of cartilage, the clear gristly stuff that your ears and nose tip are made of. And, you are correct that in its pure form, it doesn't fossilize. most sharks age, they deposit calcium salts in their skeletal cartilage to strengthen it. The dried jaws of a shark appear and feel heavy and solid; much like bone. These same minerals allow most shark skeletal systems to fossilize quite nicely. The teeth have enamel so they show up in the fossil record too.

Night shark's eye

Sharks have very good eyesight. In fact, sharks can see extremely well in dark lighted areas, have fantastic night vision, and can see colours. Avoid wearing bright colours in the water, such as oranges and yellows, as sharks can indeed see them.

It has been observed that sharks can go up to approximately 6 weeks without feeding, and the record for a shark fasting was observed with the Swell Shark, in which it did not eat for 15 months. Sharks can enter what is called an "eating phase" which perhaps might constitute hunger, but on the grand scale of things, a shark is not always hungry.

Sharks are fish. They live in water, and use their gills to filter oxygen from the water. Sharks are a special type of fish known because their body is made out of cartilage instead of bones like other fish. The classification of this type of fish is "elasmobranch." This category also includes rays, sawfish, and skates.

Sharks are omnivorous, which means they eat both meat and vegetation. Sharks will eat anything, and if there is not an abundant supply of meat in the area, they will resort to eating sea vegetation. The largest shark of all, the whale shark, is mainly a plankton feeder.

Visit our Apex Predators page for more shark information.

Contact and credits

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Taken in part from “Being a bouillabaisse of fascinating facts about fish: the most-asked questions,” NOAA Magazine, April and July of 1973.

Unless otherwise noted all color artwork is © Ray Troll 2002, © Terry Pyles, colorization 2002. These images may not be utilized in whole or in part by any entity other than NMFS without the express permission of NMFS' Office of Constituent Services and the copyright artist, Ray Troll.