Ribbon-Fishes

Ribbon-Fishes (Trachypteridae), a family of marine fishes readily recognized by their long, compressed, tape-like body, short head, narrow mouth and feeble dentition. A high dorsal fin occupies the whole length of the hack; an anal is absent, and the caudal, if present, consists of two fascicles of rays of which the upper is prolonged and directed upwards. The pectoral fins are small, the ventrals composed of several rays, or of one long ray only. Ribbon-fishes possess all the characteristics of fishes living at very great depths. They are extremely fragile when found floating on the surface or thrown ashore, and rarely in an uninjured condition; the rays of their FIG. I. - Trachypterus taenia. fins especially, and the membrane connecting them, are of a very delicate and brittle structure. In young ribbon-fishes some of the fin-rays are prolonged in an extraordinary degree, and sometimes provided with appendages (see fig. 2). There FIG. 2. - Young Trachypterus. are only two genera in the family, Regalecus, the oar-fish, and Trachypterus. In the former the length of the body is about fifteen times its depth. The head likewise is compressed, short, resembling in its form that of a herring; the eye is large; the mouth is small, and provided with very feeble teeth. A long many-rayed dorsal fin, of which the very long anterior rays form a kind of high crest, extends from the top of the head to the end of the tail; the anal and perhaps the caudal fins are absent; but the ventrals (and by this the oar-fish is distinguished from the other ribbon-fishes) are developed into a pair of long filaments, which terminate in a paddle-shaped extremity, but are too flexible to assist in locomotion. The whole body is covered with a layer of silvery epidermoid substance, which easily comes off and adheres to other objects.

FIG 3. - Oar-fish.

Oar-fishes are the largest deep-sea fishes known, the majority of the specimens observed measuring 12 ft. in length; but some are recorded to have exceeded 20 ft. Their range in the great depths of the ocean seems to extend over all seas, but, however numerous they may be in the depths which are their home, it is only by rare accident that specimens reach the surface. Thus from the coasts of Great Britain only about twenty captures are known in the long space of a century and a half, and not more than thirteen from those of Norway. Oar-fishes have been considered by naturalists to have given rise to some of the tales of "sea-serpents," but their size as well as the facility with which they are secured when observed render this solution of the question of the existence of such a creature improbable. When they rise to the surface of the water they are either dead or in a helpless and dying condition. The ligaments and tissues by which the bones and muscles were held together whilst the fish lived under the immense pressure of great depths have then become loosened and torn by the expansion of the internal gases; and it is only with difficulty that the specimens can be taken entire out of the water, and preserved afterwards. Every specimen found has been more or less mutilated; and especially the terminal portion of the tail, which seems to end in a delicate tapering filament, has never been perfect; - it is perhaps usually lost as a useless appendage at a much earlier period of the life of the fish. Of Trachypterus, specimens have been taken in the Atlantic, the Mediterranean, at Mauritius and in the Pacific. The species from the Atlantic has occurred chiefly on the northern coasts, Iceland, Scandinavia, Orkneys and Scotland. It is known as T. arcticus, in English the deal-fish; its Icelandic name is Vagmaer. Its length is 5 to 8 ft. Specimens seem usually to be driven to the shore by gales in winter, and are sometimes left by the tide. S. Nilsson, however, in Scandinavia observed a living specimen in two or three fathoms of water moving something like a flat-fish with one side turned obliquely upwards.