CHAPTER XII.

_PIKES, ARAPAIMAS, BEAKED SALMON, AND SCOPELIDS._

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

The Pikes are strictly fresh-water fishes, which are extremely voracious, and grow to a large size. They are met with in most of the fresh-waters of Europe, Asia, and America; yet they must be regarded rather as a Western than an Eastern type, since all the known species occur in America, whilst only one--the Common Pike--is known outside that country. These fishes capture their prey by stealth--practised, however, not so much by concealment as by lying suspended in the water, perfectly motionless save for the movement of the gills, which is barely perceptible. When the victim comes within reach, it is seized by a sudden rush. The form of the body is admirably adapted to this manner of feeding, resembling rather a submerged log than a fish. It is, furthermore, on account of this shape that the name Pike has been bestowed, since it recalls the "pike" borne by the soldiers of bygone days.

When on the feed, nothing comes amiss to pike, and the havoc they commit in trout-streams is enormous. Not only other fishes are devoured, but both the young and adults of water-birds are frequently seized, and instances are on record where boys have been attacked while bathing. The mouth of a pike bristles with teeth, even the roof being thickly covered. These are all attached by hinges, moving readily backwards towards the throat, so as to assist the swallowing operation, but preventing any possibility of the victim's escape.

In Great Britain the pike is held in high esteem by anglers, though as an article of food it does not find much favour. The females are larger than the males. The largest specimens attain a length of about 4 feet, sometimes a little more, and a weight of from 36 to 37 lbs.

About six species of pike are known, five of which are confined to American waters. Of these, the one known as the MUSKET-LUNGE, or MUSKINONGE, attains the same large size as the common pike; the other species are known as PIKEREL. The immature pike is commonly called a JACK.

The ARAPAIMAS are large fresh-water fishes, confined to the tropics, their distribution being practically the same as that of the Lung-fishes; they are represented in America, Australia, and Africa, but one species occurs in the East Indian Archipelago. The largest species of all--which is also the largest fresh-water bony fish known--is found in the rivers of Brazil and the Guianas, attaining a length of 15 feet and a weight of 400 lbs. It is highly esteemed as an article of food, being salted and exported from the inland fisheries to the sea-ports. The natives take it either with a rod and line, or with a bow and arrow, a line being fastened to the arrow, thus converting it into a harpoon.

Four species of arapaimas are distinguished by the presence of "barbels" on the chin; of these, two are Australian, one American, and one occurs in Sumatra and Borneo. Yet another species is found in the Nile and the rivers of West Africa. The Australian species, like the large Brazilian form, are highly esteemed as food; one of these, known as the DAWSON RIVER SALMON, is confined to the rivers of Queensland, the other to the rivers emptying into the Gulf of Carpentaria.

The BEAKED SALMON occurs in the open seas of the Cape, Japan, and Australia; but in New Zealand, where it is known as the SAND-EEL, it is found in bays with a sandy bottom.

The group of fishes known as SCOPELIDS is one of particular interest, on account of the number of remarkable forms which it contains. For the most part they are inhabitants of the open sea, many being found only at great depths. Of the latter, some apparently come to the surface to feed at night, whilst others are entirely confined to the abysses of the ocean. As with the members of other groups which have adopted a deep-sea habitat, certain modifications of the body have become necessary in these fishes. Many of them have a direct relation to the absence of light, which has rendered normal eyes of little use; consequently the eyes of these fishes have become either greatly reduced or enormously enlarged, or sometimes lost altogether. As a rule the large-eyed forms are those which come to the surface at night or do not live beyond the reach of daylight; whilst those in which the eyes are small or reduced live in the very lowest depths, far beyond the limit of daylight. In all these forms compensation for the loss of light has taken place, generally by the development of phosphorescent organs. These may take the form of a number of luminous areas distributed down each side of the body, as in the PHOSPHORESCENT SARDINE; or of a pair of lens-like light-producing organs, occupying the place of the eyes of other fishes. Another eyeless member of the group, instead of developing light-producing organs, has increased the length of the rays of the paired fins to an enormous extent, so that they serve as delicate feelers either for the discovery of food or the detection of enemies. Many of the fishes of this group have extremely large mouths, armed with a formidable array of tusk-like teeth, between which are numerous smaller ones.

As food-fishes the majority of the Scopelids are not of much value. The species known as the QUEENSLAND SMELT, shown in the adjoining photograph, is an edible species, occurring off the north-west coast of Australia. Its near ally, the BUMMALOE, or BOMBAY DUCK, however, enjoys a quite exceptional notoriety. Salted and dried, it is exported in large quantities from Bombay and the coast of Malabar, and forms an indispensable adjunct to an Indian curry. This fish apparently inhabits considerable depths, and when freshly taken is brilliantly phosphorescent. Another edible species is the "SERGEANT BAKER" of Australia, of which a photograph is given on page 653.

With regard to the deep-sea Scopelids, it is interesting to note that, in addition to very remarkable modifications of the eyes and fins, and the production of phosphorescent light, certain of the body-cavities are characterised by an intensely black coloration. The inside of the mouth, the gills, and the lining of the abdomen, for example, are always so coloured in those fishes which inhabit the deepest abysses. This coloration is difficult to account for, but it is generally supposed to be due to excretory products. Another interesting point concerns the air-bladder. Whenever this organ is present in the fishes of this or any other family inhabiting the abysses of the ocean, it bursts before the unfortunate victim is brought to the surface, owing to the enormous differences in pressure which obtain between the depths of the sea and the surface.

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