Although an occasional visitor of our shores, the Bonito, or Stripe-bellied Tunny (Thynnus pelamys), which is much inferior in size to the common tunny of the Mediterranean and the Black Sea, is a true ocean-fish, and generally met with at a vast distance from land. It inhabits the warmer seas, of which it is one of the most active and voracious denizens. It is well known to all voyagers within the tropics for the amusement it affords by its accompanying the vessel in its track, and by its pursuit of the flying-fish. But in its turn the predacious Bonito is subject to the persecutions of the huge Sperm-whale, who will often drive whole shoals before him, and crush dozens at a time between his prodigious jaws.
The Pelamid (Thynnus sarda), which abounds in all districts of the Mediterranean and on both sides of the Atlantic, has but very lately been discovered in the British waters, a single specimen having been caught a few years ago at the mouth of the North Esk. It greatly resembles the species just mentioned in form and mode of life, prowling about the high seas for cephalopods and flying-fishes, and is very commonly confounded with the bonito by sailors, who also give both of them the name of Skip-jacks, expressive of the habit which many of the large Scomberoids have of skimming the surface of the sea, and springing occasionally into the air.
Pilot-Fish.—(Naucrates ductor.)
Another member of the mackerel family, the Pilot-Fish (Naucrates ductor), easily recognised by the three dark-blue bands which surround its silvery body, will frequently attend a ship during its course at sea for weeks or even months together, most likely to profit by the offal thrown overboard. Regardless of the useful precept, "avoid bad company," it is frequently found attending the white shark, and owes its name to its being supposed to act as a trusty guide or friendly monitor to that voracious monster, sometimes directing it where to find a good meal, and at others warning it when to avoid a dangerous bait. At all events, the pilot-fish is well rewarded for his attendance by snatching up the morsels which are overlooked by his companion, and as he is an excellent swimmer, and probably keeps a good look-out, has but little reason to fear being snatched up himself.
"It has been observed," says Yarrell, "that when a shark and his pilot were following a vessel, if meat was thrown overboard cut into small pieces, and therefore unworthy the shark's attention, the pilot-fish showed his true motive of action by deserting both shark and ship to feed at his leisure on the morsels."
The family of the anguilliform fishes, characterised by their serpent-like bodies, destitute of ventral fins, and generally covered by a slippery skin, with, in some of the genera, small scales embedded therein, likewise comprises a number of highly interesting and useful species, forming many generic groups.
Its chief representative in our waters is the Common Eel (Anguilla vulgaris), which, though a frequent inhabitant of our lakes, ponds, and rivers, may also justly be reckoned among the marine fishes; for the same wonderful instinct which prompts the salmon and the sturgeon annually to leave the high seas and seek the inland streams for the sake of perpetuating their race, forces also the eel to migrate, but his peregrinations are of an opposite character, for here the full-grown fishes descend the rivers to deposit their spawn in the sea, and the young, after having been born in the brackish estuaries, ascend the streams to accomplish their growth in the sweet waters. The mode of procreation of eels, which for ages had been an enigma, has now at length been completely elucidated by Professor Rathke, who discovered that the eggs, which are of microscopic smallness, so as to be undistinguishable by the naked eye from the fat in which they lie imbedded, are expelled through an opening hardly large enough to admit the point of a needle. The energy of the salmon in swimming stream-upwards for hundreds and hundreds of miles, and bounding over rapids and cataracts, is truly wonderful, but the instinctive efforts of the little eels or elvers to surmount obstacles that seem quite out of proportion to their strength are no less admirable. Mr. Anderson, upwards of a century ago, described the young eels as ascending the upright posts and gates of the waterworks at Norwich until they came into the dam above; and Sir Humphry Davy, who was witness of a vast migration of elvers at Ballyshannon, speaks of the mouth of the river under the fall as blackened by millions of little eels. "Thousands," he adds, "died, but their bodies remaining moist, served as the ladder for others to make their way; and I saw some ascending even perpendicular stones, making their road through wet moss, or adhering to some eels that had died in the attempt. Such is the energy of these little animals that they continue to find their way in immense numbers to Loch Erne. Even the mighty fall of Schaffhausen (which stops the salmon) does not prevent them from making their way to the Lake of Constance, where I have seen many very large eels." After the little eels have gained the summit of a fall, they rest for a while with their heads protruded into the stream. They then urge themselves forward, taking advantage of every projecting stone or slack water, and never get carried back by the current. Myriads are destroyed on the way by birds or fishes; but, as usual, their greatest enemy is man, who not only devours whole cart-loads of little eels not larger than a knitting-needle, frying them into cakes, which are said to be delicious, though rather queer-looking from the number of little eyes with which they are bespangled, but after getting tired of eating them, actually feeds his pigs with them, or even uses them for manure. A prodigal waste which should be looked after, as these little eels would soon increase their weight, and consequently their value a thousand fold. On the Continent many lakes and ponds have been stocked with elvers, packed in wet grass, and sent by the railroads or the post far into the interior of the country.
Eels are pre-eminently nocturnal animals. They always congregate at the darkest parts of the stews in which they are kept, and invariably select the darkest nights for their autumnal migration to the sea. Owing to the smallness of their gill aperture, the membranous folds of which, by closing the orifice when the eel is out of the water, prevents the desiccation of the branchiæ, they have the power of living a long time out of the water when the air is humid, and not unfrequently travel during the night over the moist surface of meadows or gardens in quest of frogs or other suitable food.
That eels are not devoid of sagacity is proved by many well authenticated anecdotes. "In Otaheite," says Ellis in his "Polynesian Researches," "they are fed till they attain an enormous size. These pets are kept in large holes two or three feet deep, partially filled with water. On the sides of these pits they generally remain, excepting when called by the person who feeds them. I have been several times with the young chief when he has sat down by the side of the hole, and by giving a shrill sort of whistle has brought out an enormous eel, which has moved about the surface of the water and eaten with confidence out of his master's hand."