Fish are vertebrate animals living in water and having, instead of legs, fins which are adapted to rapid movement in the water. They breathe through gills instead of lungs.
The principal order of fish is known as the Teleostei or bony fishes. Other orders are the Elasmobranchii or fishes without a bony skeleton, Ganoidei, and a small order called the Holocephali. Fishing since the earliest recorded times has always been an industry as well as a sport with mankind. Great commercial seaports have developed from beginnings as small fishing towns, and fishing privileges are often incorporated in international treaties. The most important of the American fisheries are the cod, herring, mackerel, menhaden, halibut, salmon and whitefish fisheries.
THE ELASMOBRANCHII.
These are fishes which have no bony skeleton. In place of bone they have an elastic tissue or gristle. There are two sub-orders—those having round bodies, like the sharks and dog-fish, and those having flat bodies, like the rays and skates.
Sharks.
Shark is a general name applied to all the larger round-bodied elasmobranchii. They are powerful and rapid swimmers and many of the larger forms are found in mid-ocean. The smaller ones keep closer to the shore. Although a few are found in Arctic regions, they do not attain the great size there that they do in warmer waters. They are carnivorous, that is, they feed on animal matter, and most of them have strong teeth. The Chinese consider shark fins a great delicacy and many are exported from California to the East. The fins are also a source of gelatine.
The Tope is a small shark found in tropical and temperate seas. It averages about six feet in length. Its habit of making away with bait and scaring off other fish makes it unpopular with fishermen. The color of the tope is gray above and whitish gray beneath. It swims along the bottom of the water, feeding upon fish, crustaceans, etc. This fish is not common in American waters.
The Hammer-head Shark. The characteristic peculiarity of this shark is its broad, flat head, which accounts for its name. Its eyes are set on projections from the side of the head. They have been known to reach a length of fifteen feet. Sometimes they are seen in the North Atlantic. They are formidable and greedy. The topes and hammerheads belong to the same shark family.
The Porbeagle is a shark that is found in the North Atlantic and is known to fishermen as the Mackerel Shark. It feeds principally upon fish. A length of ten feet is attained. It bolts its food, the teeth being adapted to hold its slippery prey.