SCHOOL IN THE OPEN.

Star (Christchurch), Issue 18938, 7 December 1929, Page 24 (Supplement)

SCHOOL IN THE OPEN.

Studies in the Great Out-of-Doors.

By

J. J. S. Cornes,

8.A., B.Sc.).

The “Star” has arranged with Mr J. J. S. Comes, 8.A., B.Sc., to write a series of illustrated articles which will give teachers and others a fuller appreciation of the Great Out-of-Doors. They will deal with various aspects of plant and animal life, as well as with inanimate nature. Questions and material for identification will be welcomed.

CAPTAIN COOK’S LEATHER-JACKET.

CCCXXVI. Nearly a year ago a Lyttelton correspondent sent in one of those interesting little fish called “ Leatherjackets.” And several fishermen sent me notes of their experiences. These people, and perhaps others, will be Interested in this additional information, supplied by Tom Iredale and Gilbert Whiteley, of the Australian Museum. Captain Cook gave the name “ Leatherjacket ” to a fish caught at Botany Bay, as appears in his diary:—“ When we returned to the boat, we found that our people had caught with a seine a great number of small fish, which are well-known in the West Indies, and which our sailors call Leather-jackets, because the skin is remarkably thick.” The name must have been adopted immediately for the New South Wales fish, as, in the first publication dealing with the new colony, Tench (1789) wrote: —“ The French once caught near two thousand fish in one day, of a species of grouper, to which, from the form of a bone of the head resembling a helmet, we have given the • name of light horsemen (i.e. Snapper, unfortunately, not caught by the thousands around Sydney now—and even about Auckland, Thames, and Bay of Plenty not so common since trawline

started). To this may be added bass mullets, skait, soles, leather-jackets, and many other species, all so good in their kind as to double our regret at their not being more numerous.” The Old Wife. In California the term " Leatherjacket is also used for the Trigger, or File Fish, which belongs to the same family as the true Leatherjackets, but differs in having its sides covered, not with spines, but with rows of diamond-shaped studs, so that they are embossed like a file. This rough skin is used for scouring and polishing in place of sana-paper Ancient writers, however, used the term Old Wife to include both Leatherjacket and File Fish. Thus, in 1655 Moufet wrote: “Old Wives (because of their mumping and sour countenance) are as dainty and wholesome of substance as they are large of bodv ” and Bose, in 1816, noted that the Old Wife was so called because when caught it grinds its teeth and grumbles like an old woman. Leather-jackets. As their name indicates. Leatherjackets are covered with tough skins, and these are nearly always beset with coufttless little prickles or spines. This Skin, however, can easily be peeled off leaving in no time a clean fish ready for cooking. Leather-jackets have no ventral fins, though a flap, often supported by a spine, marks the situation where these occur in most other fishes. Thev

swim with flickering undulations of the long simple dorsal and anal fins, steered, rather than propelled, by the heavily-built, fan-like tail. Often they are attacked by a woodlouse parasite, but are hardy enough to withstand it. A dying Leather-jacket goes through a brilliant series of colour changes, impossible to describe, but such as would have delighted those Roman epicures who had their Red Mullet served alive that they might feast their eyes before filling their stomachs. Leather-jackets have strong beak-like teeth with which they can crush shellfish and Crustacea, and gnaw the growths off wharf-piles; they can also bite through fishing-lines and small hooks, and are thus most unpopular with fishermen. Indeed, when a " hookbiter ” is caught it is sometimes skinned alive, and returned to “he water, to be eaten immediately by its fellows, which desert the hooks baited fdr more acceptable fishes. Another cruel practice of Australian fishermen is to impale a cork on the dorsal spine, so that the fish floats helplessly and is eaten by others. This first dorsal spine of a Leather-

jacket is very strong and hollowed out behind at its base, to receive a peg from a second, much smaller spine. These two spines are raised or depressed simultaneously, and when the first is erect, it cannot be laid down again until the second spine, which locks it, is first depressed. Woe, therefore, to the voracious fish whose mouth or gullet is penetrated by this rigid weapon; it is even said that Leather-jackets when swallowed will retain their vitality and bite theii way out.

Food Value. Leather-jackets when of sufficient size are excellent as food. In Australia, Captain Cook’s Leather-jacket (Cantherines granulatus) is not eaten, but is, sad to say, a nuisance to fishermen because it gets caught in the nets by its dorsal spines. However, the yellow-finned Chinaman Leatherjacket (Cantherines ayraudi) is popular as food. The chief commercial species in New Zealand is the Kiriri (Catherines convexirostris). In the case of the related Trigger or File fish (which are more restricted to tropical waters and are often as brightly hued as coral fishes), the consumption of the flesh is sometimes followed by acute poisoning, the alkaloids responsible being contained in ovaries and liver. It is said that untold numbers of cats around Sydney have died as the result of eating specimens of the little Toado, common in Sydney Harbour, which have been left behind by fishermen—sometimes for that very purpose.

(To be continued next Saturday.)