NATURE NOTES

New Zealand Herald, Volume LXIX, Issue 21326, 29 October 1932, Page 1 (Supplement)

NATURE NOTES

STRANGE FISH-HOOkS

BY J. DRUMMOND, F.L.S., F.Z.S

If shark-suckers were as plentiful in New Zealand waters as they are in some other places, Maori fishermen, doubtless, would have put the strange discs on the top of these fishes' heads to practical use, as is done by native fishermen in the tropics. The disc is a singular development of the first fin on the back. It is slightly misnamed, as it is elliptical, not round. It has a rim of flesh. Across it, from side to side, are slats of tissue, equipped with spines, Mr. E. W. Gudger, an American ichthyologist, who has observed sharksuckers in an aquarium, explains that a sucker places its disc flat against the flank of a shark or of another large fish. By muscular contraction, it raises the rim and the slats, creating a partial vacuum. By the atmospheric pressure, and by the pressure of the water, the sharksucker holds fast to the larger fish, and is carried about by it. The fine spines on the slats, sticking into the skin of the larger fish, help the shark-sucker to hold on. It might be thought that the sharksucker is not a swimmer, and that it uses its device in order to have free trips through the water, The truth is it can swim quite well, and so swiftly as to catch iip with a shark. Its object merely is to share the larger fish's meals. Most sharks, Mr. Gudger joints out, have sharp, pointed teeth, suitable for tearing or broad serrated teeth suitable for chopping. With these teeth they tear or cut their prey into small pieces. Fragments torn off float in the water. A shark-sucker then relaxes the muscles of its disc, lets go, snaps up the fragments, and again fixes itself to its shark, which swims away to seek another meal for itself and for its companion. The shark does not suffer by the relationship. The disc may cause a tickling sensation, but does no harm. A shark-sucker feeds without giving anything in return, but it takes only the crumbs that fall from the rich man's table. Although it humbles itself, it is not a parasite. This type ef association is well known to zoologists. It is called commensalism. This is from the Latin " com," together, and " mensa," table, and means living at a common table. It is different from symbiosis, which means living together for mutual advantage, and from inquilinism, in which one creature becomes the tenant of - another creature without paying rent in any shape or form, and it is very different from opprobious parasitism, common in all parts of the vast and diversified animal kingdom. A shark-sucker sent to me from Auckland was about sin. long. Its disc was an inch and a-half long. In Cuban waters, shark-suckers are from 31in. to 35in. long, and their discs are 7in. long. The Cubans and other people in those parts use them fairly extensively as living fishhooks. A fisherman ties a long cord to the tail of a shark-sucker, kept on board. On arrival at the fishing-ground, he puts the gbarksucker into the water. Darting at a fish, it fixes itself to the skin. The fisherman paddles after the shark-sucker and pulls it on board with the fish the shark-sucker selected for its attention. " In this way," Lady Brassey wrote on her yacht, the Sunbeam, " one of the ugliest and most incapable looking creatures is, by savage instinct made to become of some use in procuring food for a superior animal."

When Lady Brassey, forty-seven years ago, published her account of these fishing operations, it was discredited. Later observations confirmed it. A few years a g°> I-* r - C. R. De Sola went out from a Cuban port with a party of fishermen. On a turtle being sighted, the fishermen tossed several shark-suckers into the water in the direction of the turtle. Lines tied to the shark-sucker' tails ran out quickly. They soon became taut. Vibrations showed that the shark-suckers were fast to the turtle, and the boat was rowed to the turtle, which was taken on board. As soon as it was out of the w ; ater the shark-sucker let go. All the time the fishermen talked gontly to the shark-suckers, assuring friendship, and telling them that, when they returned home, they would be fed and c;#ed for.

Turtles often are taken with sharksuckers fixed to them. Some shark-suckers seem to prefer sharks, this practice giving a name to the group, but manatees, porpoises and almost any large fish of the open sea may be selected by shark-suckers. Occasionally one fixes itself to the hull of a vessel. To prove the usefulness of sharksuckers, Dr. C. H. Townsend, director of the New York Aquarium, held a sharksucker 2ft. long by its tail while it lifteda pail of water that, weighed 211b. Another held on to a pail of water that weighed 241b., while the pail and water were raised from the ground. A sharksucker 16in. long was placed in a tank that contained other fishes. It immediately fixed itself to a fairly large groper. Both were brought to the surface by a cord tied to the shark-sucker's tail. The sharksucker let go when the groper began to struggle.

"lhe written history of these remarkable fishes begins about 440 years ago, when Columbus made his second voyage to the New World. The following clear account was given by a writer at the Court of Ferdinand and Isabella from information supplied by Columbus and his sailors:—"The most extraordinary thing is that this fish has at the back of its head a sort of very tough pocket. As soon as a fisherman sees a fish swimming near the barque he lets go the little cord. Like a dog freed from its leash £he fish 'descends on its prey and, turning its head, throws the skin-pouch over the neck of the victim, if it is a large fish. If it is a turtle, the fish attaches itself to the place where the 'turtle protrudes from its shell, and never lets go till the fisherman pulls it with the little cord ( to the side of the barque. If a large fish is caught—and fishermen do not trouble about small ones —the fishermen fasten stout cords to it and pull it into the air, and at that moment the hunting-fish lets go its prey. When the prey is in the barque the hunt-ing-fish returns to its placo and never moves, save when they give it a piece of the animal, just as one gives a bit of quail to a falcon, or until they turn it loose after another fish. The Spaniards call this fish ' reverso,' meaning one who turns around, because it is when turning that it attacks and seizes the prey with its pocket-shaped skin."

In scientific publications the sharksucker is named ratnora, meaning to delay or to hinder, The title of its order, the. Echeneidae, means to hold to a ship; tlie title of the family, Discocephali, means disc-headed. Cubans call it pecador, the sticker; and Dr. De Sola describes it as the hitch-hiker of the Seven Seas. Dr. David Starr Jordan, prince of ichthyologists, stated that the pecador is almost cosmopolitan in range, and is found on only the larger sharks. A fossil sharksucker found in Switzerland had a small disc and a compressed body, and, probably, was a much better swimmer than any living shark-sucker. Mr. Allan Bell wrote from Kaitaia, on October 7: —ln the vicinity of Spirits' Bay and of Tom Bowling's Bay, there are many thousands of acres of uncultivated land. At present it is a glory of tea-tree bloom, ranging in colour from white to the lightest of pinks and deep red. This year the tea-tree came into flower in July, and the Maoris say that this is a good omen for an abundant season."