Another peculiarity of the shark is that their colossal bodies are built upon a framework of cartilage, not bone. This may possibly account for their complete recovery from the most fundamental injuries. I once caught an eight-feet-long shark in the North Atlantic whose appearance suggested nothing out of the common. But, having a desire to make one of those useless articles dear to sailors, a walking-stick of a shark’s backbone, I went to the trouble of extracting the spine. I found to my amazement that in the middle of it there was not only a solid mass of bone of over a foot long, but it was at this place quite double the normal thickness. Further investigation revealed the fact that at some period of his career this creature had been transfixed by a harpoon which had torn out, nearly severing his body in two halves. Several of the ribs were re-knit and thickened in the same way. This splendid recuperative power renders the shark almost invulnerable, except, as before noticed, to a direct severing of the brain, or such a radical dismemberment as lopping off the tail.
Slothfulness is a distinctive feature of all the sharks. They are able to put on a spurt at times, but want of energy characterises them all. This habit reaches its climax in the Remora, to which allusion has already been made. As if in pursuance of a widely held opinion that lazy people are the most prolific inventors, this small squalus has evolved an arrangement on the top of his head whereby he can attach himself to any floating body and be carried along without effort on his part. All the functions are easily performed during attachment, and nothing short of doing damage to the fish will dislodge him. It is fairly well known that the Chinese and East African folk have utilised the Remora for catching turtle in a most ingenious way. More energetic than any other sharks are the saw-fish, whose snouts are prolonged into a broad blade of cartilage, which is horizontal when the fish is swimming in a normal position, and has both its edges set with slightly curved teeth about an inch apart. The end of this formidable-looking weapon is blunt and comparatively soft, so that it is quite incapable of the feats popularly attributed to it of piercing whales’ bodies, ships’ timbers, etc. It attacks other fish by a swift lateral thrust of the saw beneath them, the keen edge disembowelling them. Then it feeds upon the soft entrails, which are apparently the only food it can eat, from the peculiar shape of its mouth. It has an enormous number of small teeth, sometimes as many as fifty rows in one individual, but they are evidently unfit for the rough duties required of teeth by the garbage-eating members of the family.
Another peculiarity which differentiates the Squalidæ from all other fish, and would seem to link them with the mammalia, is the way in which they produce their young. But here arise such diversities as to puzzle the student greatly; for some sharks are viviparous, bearing fifteen sharklets at once, that play about the mother in the liveliest manner, and are cared for by her with the utmost solicitude. At the approach of danger they all rush to the parent and hurry down her throat, hiding in some snug chamber till their alarm has subsided, when they emerge again and immediately recommence their gambols. The pretty little blue and gold Caranx (pilot-fish) that is so faithful a friend and companion to the shark also hides at times in the same capacious retreat. That this is a fact cannot be disputed, since sharks have often been caught and cut open, and the lively prisoners taken from within. Upon several occasions I have witnessed this, and I once kept a family of a dozen for over a week in a tub of water, feeding them on scraps, until some busybody gave them to the cat and made her very unwell. I have also seen the young ones and the pilot left behind when a shark has been caught, their frantic leapings upward at their departing protector being quite a moving sight. Other sharks are ovoviviparous, laying eggs over the hatching of which they watch and afterwards care for the young as tenderly as do the others. Another species pack their eggs in a sort of pouch as the skates do. This envelope contains all the nourishment necessary to the well-being of the young until they are able to provide for themselves, but the parent has no further concern with them. As instances of the intelligence of the shark many well-authenticated stories might be told did space permit, but two must suffice. While lying in the harbour of Tamatave every device we could conceive was put in practice in order to catch some of the sharks with which those waters abounded, but none were successful, for they carefully avoided all bait attached to lines strong enough to hold them. And the well-known habit of the “thresher” shark (Alopecias vulpes), of hunting with the killer-whale (Orca gladiator), assisting these furies to destroy a whale and afterwards amicably dividing the spoil with them, has been enlarged upon many times. Its absolute certainty does not admit of a doubt.
XVII
FLYING-FISH CATCHING AT BARBADOS
Among the many divers methods of garnering the harvest of the sea, one of the most interesting and peculiar is the Exocetus fishery of Barbados. Notwithstanding the incredible numbers of Flying-fish (Exocetus volitans) that crowd every tropical sea, Barbados is the only place where a systematic fishery of them has ever been established for commercial purposes. This is the more strange when the ease with which they may be taken, and the pleasant conditions under which the fishery is carried on, is considered, while the succulent delicacy of the fish is certainly a thing to remember. Familiar as the appearance of these wonderful little creatures is to ocean travellers, very little is generally known with regard to their habits, haunts, and mode of life. They are usually the recipients of much misspent pity. Relentlessly pursued by the albacore, bonito, and dolphin, they seek the air in shoals, only to be gaily annexed by hovering birds, or to fall gasping upon the deck of some passing ship. Their fate seems a hard one; but who pities their prey? They in their turn pursue as relentlessly and persecute as ruthlessly the smaller fish; and so the balance is held as truly as nature ever holds it where man does not interfere.
The most common and widely distributed variety of the flying-fish is E. volitans, whose range is world-wide between the limits of about thirty-five degrees north and thirty degrees south, though they are most plentifully found within the tropics. They are usually from six to twelve inches in length, body nearly quadrangular, colour of the head and back blue, abdomen silvery, lower lobe of the tail one-half longer than the upper. Some have no teeth, while others are well furnished; and naturalists are unable to agree as to whether they are different varieties, as they are in all other respects identical. The pectoral fins, or wings as they might well be called, are nearly as long as the fish, folding neatly and compactly into the sides of the body while the fish is in the water. The ventral fins are small in this species, and do not appear to be used as wings, merely serving to balance and guide the fish in the air. A very common error made in natural histories where this fish is mentioned is in the statement that it does not fly. “Its supposed flight is nothing more than a prolonged leap; it cannot deviate from a straight line, and cannot rise a second time without entering the water.” This, briefly, is the sort of thing one meets with in text-books where reference is made to this fish.
The simplest way of dealing with it is the Professor’s method of answering the query of the French Academy whether their definition of a crab was correct. The story is so well known that it does not need repetition. As the result of personal observation extending over a good many years, I assert that the Exocetus does fly. I have often seen a flying-fish rise two hundred yards off, describe a semicircle, and meeting the ship, rise twenty feet in the air, perpendicularly, at the same time darting off at right angles to its previous course. Then, after another long flight, when just about to enter the water, the gaping jaws of a dolphin emerging from the sea gave it pause, and it rose again, returning almost directly upon its former course. This procedure is so common, that it is a marvel it has not been more widely noticed. A flying-fish of mature size can fly a thousand yards. It does not flap its fins as a bird, but they vibrate, like the wings of an insect, with a distinct hum. The only thing which terminates its flight involuntarily is the drying of its fin membranes, and their consequent stiffening.
A marvellous provision of nature is apparent in the economy of this fish. Its swim-bladder can be inflated so as to occupy the whole cavity of the abdomen. Another membrane in the mouth is inflated through the gills. These two reservoirs of air form an excellent substitute for the air-cells within the bones of birds, and have the additional advantage of being voluntary in their action.
The only other species of flying-fish which is sufficiently distinct to call for notice is E. nigricans, locally known as ‘Guineamen.’ They often exceed eighteen inches in length, and weigh two or three pounds. In these the ventral fins are also very large, giving the fish the appearance of a huge dragon-fly as it darts through the lucent air. The markings of the body are black instead of blue, while the fins are black with a transverse band of silver.