CHAPTER XV.

_BONY PIKE, BOW-FIN, STURGEON, REED-FISH, AND BICHIR._

BY W. P. PYCRAFT, A.L.S., F.Z.S.

The present chapter deals with the remaining forms belonging to that great assemblage of fishes known as the Bony-mouthed group, which includes all the members of the class save the Lung-fishes on the one hand and the Shark Tribe on the other.

This great assemblage, as we have already remarked, is divided into two sections--the Fan- and Fringe-finned Fishes. The fishes presently to be described belong partly to the one and partly to the other of these divisions, and were at one time, together with the Lung-fishes, regarded as nearly allied, and as forming but a single group, which, on account of the structure of the scales, was known as the Enamel-scaled group.

The BONY PIKE, the BOW-FIN, and the STURGEON are the last of the Fan-finned Fishes.

The BONY PIKE, or GAR-PIKE, is an inhabitant of the fresh-waters of North America, and has the most completely ossified skeleton and the most perfectly jointed backbone of all the fishes, whilst externally it is covered with a complete armour of thick, quadrangular scales coated with enamel. Three distinct species of this family are known, all of which are of large size, attaining a length of 6 feet. They are carnivorous in their habits, lying in wait among the reeds, and rushing out to seize their prey as soon as within range. In the Mississippi, great lakes, and rivers of South Carolina bony pike are especially abundant, occurring at times in such numbers as to fill the shad-nets and render the fishery for many days impossible. The larger members are said to be as aggressive as sharks, and remarkably tenacious of life.

The geographical distribution of the BOW-FIN closely corresponds with that of the bony pike. It is an extremely common fish, and, though worthless for food purposes, has yet been deemed worthy of a number of different names, such as GRINDLE, DOG-FISH, SAWYER, MUD-FISH, and LAWYER-FISH. At one time it was regarded as a near ally of the Herring Tribe, but modern research has shown this view to be erroneous. The bow-fin attains a length of about 2 feet, and is very voracious, preying both upon other fishes and aquatic insects and shrimps. It has a habit of coming frequently to the surface to breathe, especially when the water is foul, taking in large mouthfuls of air. When near the surface, it is said to utter a bell-like note, probably caused by the escape of air from the air-bladder. During the breeding-season the male takes entire charge of the eggs.

The STURGEONS differ from the other fan-finned fishes in many particulars. To begin with, the skeleton is almost entirely cartilaginous instead of bony, whilst externally the body is either naked or covered with bony bucklers, arranged symmetrically. The snout is prolonged into a more or less shovel-shaped beak, used for turning over the mud at the bottom of the water in search of prey, and in some forms this becomes further developed into a spoon-shaped paddle, constituting one of the most remarkable appendages of fishes.

Sturgeons grow to a large size, and are the largest of the fresh-water fishes of the northern hemisphere. The GIANT STURGEON of the Black and Caspian Seas and the Sea of Azoff attains a length of 24 feet, and sometimes more, specimens of 3,200 lbs. weight having been recorded.

On account of the wholesomeness of their flesh, sturgeons are highly esteemed wherever they are found. In Russian rivers they are very abundant, regular fishing-stations being established for their capture. The approach of a shoal of fish is announced by a watchman, and it is said as many as 15,000 sturgeon have been captured at one of these stations in a single day. Should the fishing be suspended for a short time, the fish assemble in such numbers as to form a solid mass, completely blocking a river 400 feet in width and 25 feet in depth.

From the roe of these fishes caviare is made, and isinglass from the inner lining of the air-bladder. But the best-flavoured flesh and the finest caviare are obtained from a comparatively small form, the STERLET, a species which does not exceed a yard in length. It is common in the Black and Caspian Seas, the Siberian rivers, and the Danube as far as Vienna.

With the Sturgeons we come to the end of the Fan-finned Fishes. The Fringe-finned group are represented to-day only by the BICHIR and the REED-FISH. These are extremely interesting forms, if only because they are the sole survivors of a once numerous tribe, the remains of which occur as fossils in some of the oldest geological formations. They are known as Fringe-finned on account of the fact that the rays which support the fin-membrane in the paired fins are ranged round a lobe-shaped base, instead of running directly backwards to the body. As in the bony pike, the body is clothed externally by large quadrangular bony plates of considerable thickness, and coated with a layer of enamel.

The BICHIR, which is found in the Nile and other tropical rivers of Africa, is easily recognised by the peculiar structure of the back-fin, which takes the form of a series of detached finlets, varying in number from eight to eighteen. The length attained by the bichir is about 4 feet. Gill-breathing is supplemented by the air-bladder, which is used as a respiratory organ, the expired air escaping by a slit, known as the "spiracle." The young bichir breathes, like a tadpole, by means of large external gills, projecting backwards on each side of the head; later these are replaced by the more efficiently protected internal gills.

The only surviving relative of the bichir is the REED-FISH of Old Calabar, which differs by its eel-like form and the absence of the hinder paired fins.

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