One of the rarest and at the same time most strongly differentiated sharks on the coasts of the United States is the cow shark (Hexanchus griseus), at once recognizable by its single dorsal fin, and its six gill apertures. The dentition also is peculiar (in the front of the tipper jaw there are four pointed teeth, on each side of which are three with one or several cusps, and laterally the teeth have many cusps; while in the middle of the lower jaw there are a small tooth with or without a cusp, and lateral serrated teeth with many cusps). There appears to be only one instance of the occurrence of’ this shark in our waters, although it is said by Poey to be often found about Cuba. An individual ten feet two inches long was taken in 1886 at Currituck Inlet, N. C., a plaster cast of which is in the United States National Museum. On the shores of western and southern Europe, where the cow shark is most common, it attains a length of twenty-six feet or over.
Among the most interesting sharks of the world are the deep-sea species. The extreme depth at which sharks have been found is about one and one-sixth miles. The deep-sea forms are for the most part small, of a blackish or dark brownish color, and do not exhibit any marked structural differentiation from the littoral and pelagic species. There have been taken off the east coast of Africa and in the Gulf of Aden (on the “Valdivia” cruise), at a maximum depth of 1,006 fathoms, several specimens of a hitherto unknown shark (Apristurus indicus). The largest is thirteen inches long. This species inhabits a greater depth than any other shark, as far as known.(7)
One of the most striking of the deep-sea sharks is a form taken by the “Albatross” in Batangas Bay, Luzon, Philippine Islands, at a depth of one hundred and seventy fathoms (it was made the type of a new genus and called Squaliolus laticaudus by Smith & Radcliffe. It is cylindrical, slender, with very narrow peduncle and very broad tail, and is jet black, with the fins wholly or partly white. The species is represented by a single pair, of which the fully developed male (which is larger than the female) measures less than six inches in length. It is believed that no other shark is so diminutive.
We have not yet spoken of the largest of all sharks—which means the largest of all fishes of the world. This is the “whale shark” (Rhinodon typus), originally described from Cape of Good Hope, but now known from India, Japan, South America, Panama, California, and various other places. There have been two individuals taken on the coast of Florida, the first, a rather small one (eighteen feet long) obtained at Ormond in 1902; the second a veritable monster, caught at Knight’s Key in June, 1912. The skin of the fish was stuffed in a distorted shape (see photo below) and exhibited in various parts of the country as “The Only Creature of the Kind in the World.” The advertised length of the fish was forty-five feet, but from the best information obtainable it was somewhat more than thirty-eight feet long before stuffing.
This shark has a very broad and obtuse snout and an exceedingly wide mouth armed with numerous minute teeth; the dark-colored body is marked with many small whitish spots. The species is stated to attain a length of seventy feet and is known to exceed fifty feet. Notwithstanding its immense size, however, it is harmless to man unless attacked, and feeds on the small creatures for which its teeth are adapted. Its huge bulk makes it dangerous in the same way that a whale is dangerous. Years ago it was reported that the sperm-whale fishermen on the island of Saint Denis, in the Indian Ocean, dreaded to harpoon a whale shark by mistake, and stories are told of how a harpooned fish “having by a lightning-like dive exhausted the supply of rope which had been accidentally fastened to the boat, dived deeper still, and so pulled a pirogue and crew to the bottom.”
The sharks most numerous on the United States coasts are the small forms known as dogfishes, which belong in two distinct families and get their name from their habit of going in droves or packs like wild clogs. The smooth dogfish (Mustelus canis), is one of the omnipresent fishes of the Atlantic coast in summer from Cape Cod to Cape Hatteras, and is abundant on the lower Carolina coast in spring. It is a slender graceful species, without spines in the dorsal fins, reaching a length of three feet, and having pavement-like teeth adapted for crushing lobsters, crabs, and other bottom-loving creatures. The horny or spiny dogfish (Squalus acanthias) is found on both sides of the North Atlantic and is easily the most abundant and most destructive of our east-coast sharks. The spiny dogfish ranges as far north as the Gulf of St. Lawrence and south to North Carolina, and reaches its maximum abundance north of Cape Cod. Coming along our shores in schools containing untold millions, and one school following another often with slight intermission, these fishes do immense damage for fishermen by devouring or mutilating the food fish taken in the gill nets, by eating the bait and the line-caught fish, by chewing and tearing nets and lines, by filling pound nets to the exclusion of other fish, and by devouring lobsters in and out of the lobster pots. When the schools of dogfish appear, the fishermen must abandon their efforts, and the loss of fish and apparatus is thus supplemented by loss of time. There have been seasons when the damage to the fisheries of the New England coast by this one species has been fully a million dollars. The loss is accentuated by failure of the fishermen to make any use whatever of the dogfish because of the lack of a market demand in the United States, notwithstanding that the fish is wholesome and nutritious and is very extensively eaten in western and southern Europe.
One of the great American needs at the present time is the shark-eating man. All sharks of sufficient size have a food value, and in many parts of the world sharks are regularly fished for and used for human consumption. In the United States the utilization of sharks has been negligible for several reasons; notably because of the abundance and variety of other food fish, and because of our ignorance of their food value, and our deep-seated prejudice on account of their unsavory reputation as consumers of the most promiscuous materials, including living and dead human beings. It may prove to have been a very unfortunate coincidence that the killing of Americans by sharks should have come at the very time when the Bureau of Fisheries was inaugurating a campaign to induce the wholesale consumption by Americans of one of the most destructive, though least dangerous, species of sharks. It remains to be seen whether, in spite of this untimely handicap, a movement in the interest of fishermen and fish consumers, based on indisputable economic facts, will not succeed.
The Congress of the United States, at the recent session, appropriated $25,000 to enable the Commissioner of Fisheries to conduct investigations and experiments for the purpose of ameliorating the damage to the fisheries done by the dogfish and other predacious fishes. The act is aimed primarily at the spiny dogfish, and the task before the Bureau of Fisheries is to convert an unmitigated nuisance into a valuable asset.