Sharks, Skates and Rays

       Many strange things are found in the sea; but none of them are stranger than the sharks skates and rays. To begin with, these fish are unlike all others because they have a skeleton made largely of cartilage instead of bone and because the gill slits through which they breathe have no covers. If you examine the fish skeletons, you will see how the shark and ray skeletons differ from those of other fish.

       Sharks are better known to most of us than the other members of the family because we have heard so many stories of man-eaters. All sharks eat animal food; and many of them like their food alive; but of the hundred and fifty different kinds of sharks, there are only but a few large enough to eat a man!

       One of the large sharks which is greatly feared by people who live on the margins of the warm seas, is the Tiger Shark. Their baby sharks show us where this fish gets its name. The stripes which are so dark on their babies gradually fade as the shark grows older and finally disappear. Tiger Sharks prey upon other sharks and upon turtles, crabs, swimming birds and fish. In fact, they apparently consider any animal which they find in the water a proper article of diet; and they must, therefore, be considered dangerous to man. The Tiger Shark sometimes grows to a length of thirty feet. It is seldom seen alone; but usually prefers to go with others of its kind in schools.

       The Tiger Shark sometimes visits east coast; but far more often, the fishermen there are bothered by great schools of smaller sharks which, at certain seasons of the year, make fishing for mackerel, shad, etc., almost impossible. Of these, the Dogfish, which come in packs like wild dogs, are particularly troublesome. They swim along the fisherman's gill net and eat the fish caught there. They get into his pound nets and devour the catch. They take his bait from his line. They catch his lobsters both in and out of the lobster pots or traps; and, besides all this, they do great damage in tearing and destroying his nets and other fishing tackle.

       For many years, fishing practically ceased during the shark season; but now fishermen are beginning to discover that the shark itself is useful and to catch it. The flesh of the Dogfish is canned and sold under the name of Grayfish or spiny dogfish; and the flesh of even the large sharks often finds its way to the markets as Deep Sea Swordfish. 

       Old Tanneries long ago, established on the east coast, made leather from the shark's skin. When the rough, horny, outer covering was left on it, it was called shagreen‚ and it was used, in America for polishing wood. When the outer covering was removed, a soft leather, suitable for shoes, luggage, pocket books, furniture covering etc., could be made. The shark's liver was used for making an oil similar to cod liver oil; and its fins are sometimes still sent to China to be used in making gelatine (shark fin soup).

In earlier geologic ages, sharks were much larger than they are now.
Some of them grew to a length of eighty feet.
Above is a reconstructed Megalodon skeleton from Calvert Marine Museum.

       Skates and rays are little more than flattened sharks; but their teeth are, for the most part neither as large nor as sharp as those of the sharks; so they have learned to defend themselves in ways other than by biting. The Eagle Ray is one of the Stingrays. It defends itself by lashing its tail back and forth and inflicting painful and dangerous wounds with the barbed spine or sting which is attached to the base of its tail. The Sawfish has a toothed saw on the end of its nose which it uses in fighting. The Torpedo, or Electric Ray, generates an electric current in a peculiar organ which lies near the back of its head. It uses the current to stun or kill the small fish upon which it feeds as well as for defense. It is said that a large Torpedo can give off enough electricity to knock a man down. Cockrell.

Deep Look "How do sharks and rays use electricity to find hidden prey?"