CHAPTER XVI.

_SHARKS AND RAYS._

BY F. G. AFLALO, F.Z.S.

Two prevalent errors with reference to sharks continually recur in England. The first is local, and has reference to the absence of "proper" sharks, whatever that may mean, from British waters. The second, of wider application, holds that all sharks are dangerous to man. When, some few years ago, the writer addressed a letter to the Times newspaper, warning yachting-men against summer bathing in deep water in Cornwall, a host of critics accused him of a tendency to pose as an alarmist, and insisted that he was confusing sharks with dog-fish. Apart from the fact that the distinction between the two groups is in some cases extremely slight--it does not even rely on size, for there are dog-fishes which attain to larger dimensions than the smallest sharks--these gentlemen were wholly in error, since four sharks at any rate are very common in Cornish seas, and even occur in lesser numbers on other parts of the British coasts. The largest of these, the great BASKING-SHARK (of which a photograph, taken at Mevagissey, is given below), illustrates in its harmless person the fallacy of condemning all sharks as man-eaters, since in this, the largest of its race, we have an absolutely innocuous fish. From its habit of lying at the surface with the large back-fin erect, it is also known as the Sail-fish, while the equally appropriate name of Sun-fish sometimes causes confusion with other British fishes properly so called.

A commoner British shark (in the limited space allotted, British species must be allowed prior claims) is the BLUE SHARK, small examples of which, weighing 30 or 40 lbs., the writer has often killed with the rod at Mevagissey. When thus hooked, this fish has a curious and very trying habit of revolving rapidly in the water, scoring its own granulated skin with the line. The PORBEAGLE-SHARK, another Cornish species, is of thicker build than the last, and swims with far less graceful movements. It is a deep brown colour above, and its general outline may be likened to that of a torpedo. The FOX-SHARK, or THRESHER, so often seen on hot summer days leaping out of water among the pilchard-shoals, is easily recognised, even at considerable distances, by the disproportionately long upper lobe of the tail-fin. This is the shark which attacks certain of the Whale Tribe. Many who stay at home find it agreeable to cast doubt on the story; but the writer has, in Australian seas, witnessed the sight of two of these sharks flinging themselves on the back of an apparently exhausted whale in such unmistakable circumstances that the only alternative (which the reader may accept, if preferred) is to suppose that they were all congenial playmates.

Before specifying some general characters of this interesting group of predatory fishes, it may be as well briefly to summarise the BRITISH DOG-FISHES; for the HAMMERHEAD-SHARK, very common in southern seas, is so rare a visitor to Britain as to be negligible in an epitome of the group. The dog-fishes, then, which trouble fishermen are the SMOOTH HOUND and ROUGH HOUND, the NURSE, the PICKED DOG, and the SILVER DOG, or TOPE. The NURSE and ROUGH HOUND are spotted leopards of the sea, and the latter has a very curious property. If a fresh-caught "row-hound," as the fishermen pronounce the name, be put in a basket or boat's well with pollack and other fishes, the points of contact will be marked by discoloration of its neighbours. This is probably due to some acrid and bleaching secretion of the row-hound's skin, for which some economic use might possibly be found. The PICKED DOG, or SPUR-DOG, has very sharp spines in front of both back-fins, and has therefore to be handled by the fishermen very cautiously, often punishing their hands badly when entangled at night in the nets. Of SMOOTH HOUNDS there are two species or varieties, between which there is some confusion, and in one at any rate there are interesting anatomical peculiarities in the unborn fish (like many other sharks and dog-fishes, the smooth hound bears living young instead of depositing eggs), any account of which would obviously be out of place in so short a description.

Generally speaking, then, the sharks are cartilaginous fishes, having the upper lobe of the tail larger than the lower, a shovel-shaped snout, and the crescent-shaped mouth beneath the head. Another peculiar feature of the group is the presence of breathing-spiracles behind the eyes; while the latter have a manner of blinking not found in other fishes. Of the teeth, which differ in structure from those of other kinds of fishes, there are several rows. The gill-openings are lateral, and usually number five, though one species has six and another seven. With the exception of the afore-mentioned BASKING-SHARK and the PORT JACKSON SHARK, which the writer met with in Australia, they are all more or less dangerous; and when of insufficient size to be harmful to man, do great damage among the lines and nets of the fishermen. Indeed, the late Matthias Dunn of Mevagissey seriously urged on the Admiralty to dynamite them in the interests of the fishing industry. Most of the sharks deposit their eggs in the curious oblong vessels known by those who pick up the disused cases on the foreshore as "purses"; and these attach themselves to rocks and stones by long tendrils that cling to every support. A number of species (the PORBEAGLE and TOPE among British kinds), however, bring forth their young alive.

Between the Sharks and Rays there is a curious and interesting link in the form of the MONK-FISH, or ANGEL-FISH, which is common on all sandy shores, and a frequent victim of the trawl. Such local names as Mongrel-skate and Shark-ray indicate a widespread acceptance of its intermediate position between the two groups under notice. Like some of the sharks already noticed, it produces living young, and its maximum size may be set down as at any rate over 7 feet. The writer measured and weighed one trawled in Bournemouth Bay during the summer of 1896. Its length was nearly 4½ feet, and its weight rather less than 50 lbs. Like many of the rays, this species feeds to a great extent on flat-fishes.

In outward form the monk-fish, though it is in reality more nearly allied to the sharks, brings us by an easy transition to the flattened RAYS, with their long whip-like tails and pointed snouts. There are a dozen, or rather more if we count casual visitors, of these skates and rays in British seas, the largest being the great EAGLE-RAY, examples of which have been recorded of the enormous weight of 1,000 lbs. Many of the smaller kinds are studded with sharp spines, curved in some species, and the THORNBACK owes to these its trivial name. All these rays, in fact, have some form or other of formidable offensive and defensive apparatus. The STING-RAY has on its tail a fearful serrated dagger, 6 or 8 inches long in large examples; while the TORPEDO- or NUMB-FISH has electric organs in the head, with the aid of which it can give a shock sufficiently strong to paralyse the fishes on which it feeds.

Two interesting peculiarities of the rays deserve notice in concluding this chapter. The first is that their egg-purses, instead of attaching themselves with filaments to weeds and rocks, like those of the sharks, are provided with a sticky secretion which answers the same purpose of anchoring them in security from currents that would carry them out into deep, cold water. The second is the sexual difference in the teeth, which are pointed in the male and flat in the female. Whether this difference in the teeth (which may be likened to that between the bills of the male and female Huia-bird of New Zealand) indicates a corresponding difference in food, or, on the other hand, some co-operation between the sexes in procuring it, is an interesting question that our present slight knowledge of the habits of these fishes does not enable us to answer.

Finally, attention must be drawn to the remarkable transformation which the breast-fins and tail have undergone. The former have developed into powerful swimming-organs, locomotion being effected by their undulatory movements, instead of by similar movements of the whole body, or by side-to-side motions of the tail, as in other fishes. Whilst the latter, no longer used in swimming, has either been reduced to a mere vestige, as in the HORNED OX-RAY, or has become developed into a long and tapering "whiplash," provided with a poison-spine. In such cases the long tail is used to encircle prey, and at the same time to force the victim on to the deadly spine.

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_BOOK V. JOINTED ANIMALS._

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