CHAPTER X.

_EELS AND CAT-FISHES._

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

Eels, like flat-fishes, show plainly, in the shape of their bodies, a remarkably perfect adaptation to their environment. They are burrowing fishes, passing much of their time buried in the mud, and leaving little more than the head exposed. In accordance with this habit, the body is very long and round, and lacks both the hinder paired fins, and scales. When swimming, the body is propelled by rapid undulations, the movement being from side to side, it may be remarked, instead of up and down, as in the "serpentine" movements of snakes.

Whether all the fishes commonly regarded as eels really belong to this family or not is a moot-point. It is possible that the eel shape has been independently acquired by unrelated forms as a result of adaptation to a similar mode of life. But as the group now stands it embraces several distinct types,--the COMMON FRESH-WATER EELS; numerous marine species, such as CONGERS, SERPENT-EELS, DEEP-SEA EELS, and PAINTED EELS; and the fresh-water ELECTRIC EELS.

The RIVER-EELS and CONGERS are perhaps the best known, and are also highly important food-fishes. That they are fishes of comparatively slow growth seems to be shown by the fact that the common eel takes about four or five years to attain a weight of between 5 and 6 lbs. The males are smaller than the females, the greatest length attained by the former being a little over 1 foot 7 inches, whilst the latter may attain a length of nearly 4 feet. For a long while what is now known to be the female river-eel was regarded as a distinct species--the SHARP-NOSED EEL. The two sexes have quite different habits, the smaller males being found mostly in the brackish water of river-mouths, and rarely above the reach of the tides, whilst the females ascend the rivers for great distances, thousands finding their way into isolated ponds, which they reach by travelling overland. Here they appear to remain till they have reached maturity, when they migrate with one accord to the sea. Coming down the rivers during the months of October and November, hundreds are taken in large niches with traps, the mouths of which are directed up-stream.

The migration of eels to the sea is for the sole purpose of spawning and fertilising the eggs, which done, they die. The spawning appears to take place in extremely deep water, where the young eels pass the earlier stages of their development. Like the majority of young fishes, the fry are at first very different in form from the adults, and many have from time to time been described as distinct species, no suspicion of their true nature having been aroused. And this is not to be wondered at, for at this stage they are perfectly transparent and compressed from side to side, so as to be but little thicker than a sheet of stout paper; the head is ridiculously small, and only median fins are present. As development proceeds, having reached a certain maximum size, they, strangely enough, begin to slowly diminish, growing shorter and at the same time rounder, so that eventually, by the time the characteristic eel form is attained, they are considerably shorter than they were at the maximum period of larval life.

By the time the adult eel form has been attained, the larvæ have made their way to the mouths of various rivers, preparatory to making their ascent, which takes place between February and May. They are then from 2 to 5 inches long, and perfectly transparent save for a black line inside the body, running along the spinal cord. The numbers passing up a single river during this ascent are almost beyond belief. In one of these migrations, or "eel-fares," upwards of three tons were captured in a single day in the Gloucester district in 1886, and it has been calculated that more than 14,000 go to make a pound weight. In the previous year the annual consumption of eels was estimated at a minimum of 1,650 tons, with a total value of £130,000. Few obstacles seem too great to be overcome in their ascent, for they will ascend the flood-gates of locks, or even travel overland if the ground be wet, till a desirable resting-place is found. In some parts of England these young eels, or "elvers," as they are called, are salted and made into cakes.

The CONGER-EEL is a marine species, differing from the river-eel, amongst other things, in its larger head and eyes, and in the arrangement of its teeth and the large size of the gill-openings. The conger is also greatly superior in size, examples of between 6 and 7 feet in length and 60 lbs. in weight being common. The females are larger than the males, and an instance is on record of a female which was over 8 feet in length and weighed 128 lbs. Congers feed on other fishes, cuttle-fishes, and lobsters, as well as upon one another, the larger females eating the smaller males.

SERPENT-EELS are confined to tropical and sub-tropical seas, and are remarkable for their extreme voracity. More than eighty species are known, some of which are brilliantly coloured.

The DEEP-SEA EELS are represented by numerous species, and dwell at depths varying from 340 to 2,000 fathoms. In some species the body is remarkably modified, the mouth being of enormous size, and the stomach capable of marvellous distension, so much so that eels of this family have been captured which had swallowed fishes several times their own weight. The tail in many of the deep-sea eels tapers to a fine hair-like point.

The PAINTED EELS are remarkable for their bright spotted or mottled coloration, and are of large size, ranging from 6 to 8 feet in length. Armed with formidable teeth, the larger species are held in no little fear by fishermen and bathers, attacks from these fishes being by no means rare. Their distribution is closely similar to that of the Serpent-eels.

The ELECTRIC EEL is an extremely abundant fish in the rivers and lagoons of Brazil and the Guianas. It is the most powerful of the electric fishes, and attains a length of 6 feet. The electric organs of this fish are sufficiently strong to kill by their shock other fishes and even mammals. The traveller Humboldt is responsible for the statement, now generally discredited, that the Indians procured this fish by driving horses into the water, and so provoking such violent discharges from the fish that they became exhausted and fell an easy prey.

The CAT-FISHES, or SHEATH-FISHES, are an extremely interesting group, one of the principal characteristics of which is the total absence of scales, the body being either entirely naked or armed with bony tubercles or overlapping plates. Another peculiarity of these fishes is the presence of feelers round the mouth; these, by their delicate sense of touch, enable the fish to procure its food in extremely muddy water, when the eyes would be useless. The latter, indeed, in many species are extremely reduced in size. Many cat-fishes are armed with powerful spines, attached to the body by a very complicated mechanism. Such spines are capable of inflicting dangerous wounds, either by the introduction of poison or the violent inflammation following on the laceration of the wounded part. Some species have elaborate accessory breathing-organs, enabling them to travel overland for short distances from one piece of water to another. Other members of the group possess electrical organs of considerable power; one species inhabiting the Nile attains a length of 4 feet.

The nesting-habits of the group are exceedingly interesting, some building nests in which to deposit the eggs; others carry the eggs in the mouth till they hatch. In one species the care of the eggs is undertaken by the female, which carries them about embedded in the skin of the under surface of the body, which at this season becomes very soft and spongy. When the eggs are laid, she presses them into the spongy skin by lying on them.

The cat-fishes are of world-wide distribution, but only one species, the WELS, occurs in European waters. It commonly attains a length of from 6 to 9 feet, and occasionally as much as 13 feet. The majority of cat-fishes inhabit fresh-water, but some are marine.

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