The Trochus.

A Peep Into Its Private Life.

From Our Own Correspondent.

Thursday Is., June 15.

NOTES on Trochus Niloticus” is the title of a short monograph written by Mr. F. W. Moorhouse, B.Sc., marine biologist to the Government of Queensland, dealing with an article ex ported from several parts of the Pacific.

A pamphlet confined to the subject of “a primitive gastropod belonging to the Rhipidoglossa” does not promise much interest to a non-scientific reader, but, as a matter of fact, one becomes absorbed at once in reading of the habits of the fish, and, considering its economic value and the very useful in formation that Mr. Moorhouse supplies, we feel it should be in the hands of everyone who is connected with the trochus industry.

The pamphlet is published by the British Museum at 1/-, and, in all pro bability, copies could be obtained from the Department of Marine Biology, Brisbane. Mr. Moorhouse’s work on the trochus is an example of the effective way in which science assists in busi ness development. The salient points of his investigations are herewith given.

The trochus was given the specific name of Niloticus in error. The first specimen brought to England undoubt edly came from the South Seas, but, by some mistake, it was supposed to in habit the waters of the Nile, and was named accordingly.

The trochus is, however, only found in the Western Pacific and Eastern Malayan region, such as the Arafura and Coral Seas, Barrier Reef channels and along the coasts of New Guinea, Solomons, Fiji and New Caledonia. It is not found in the Eastern Pacific.

It prefers the windward (south-east) side of the reef, avoiding sandy, muddy or grassy localities. An important fact, as stated by Mr. Moorhouse, is its confinement to shallow water, not greater than 3 feet in depth at lowest springs, which was proved by the author at Low Island, where the sub ject was especially studied. This avoidance of deeper waters is not, how ever, in accordance with the experience of the trochus fishers of Torres Strait, who are accustomed to retrieve shell from four to six fathoms.

At Low Island, many specimens were found in water that dried off between tides, when it creeps under boulders, and the fish can exist for long periods out of water altogether—revival having taken place after two days ashore.

Small specimens are found at the level of high water neaps, and they increase in size to a depth of half a fathom at low water springs. Wherever their usual food (a seaweed growing along the fringes of the coral reefs) is found, the trochus congregates in great numbers.

That the fish is given to wandering is a well-known fact among divers; at Low Island a marked specimen was found to have moved over 50 yards In one night.

Of more practical importance is the "age-size” ratio as worked out by Mr.

Moorhouse, which is measured by the diameter of the base of the shell. Ani mals of one inch are considered to be about one year old, and they increase

by one inch approximately for each year of life. The official limit of inches therefore represents at least two-year-old fish.

The sexes are separate, and repro duction takes place during the second year of life. The eggs are freed in the water a few at a time during the lay ing season, which is a long one, last ing certainly from March to July and probably much longer.

During the winter months, there is a slackening off in the amount of shell deposited by the animal, and the trochus passes through a period of true hibernation, feeding but little and re maining under the rocks or crevices in the coral. This explains the assertion sometimes made that the fish “migrate" in the winter.

Trochus Farms Possible.

It has been stated several times by scientists, who have worked at trochus investigations on the Barrier, and who ought to know the economics of the matter, that there is a living to be made in the culture of this shell —in short, a trochus farm. So far, no one has been enterprising enough to go

into the business, but it seems quite feasible, given good feeding grounds, plenty of clear moving water, and shallow basins for preventing straying.

It takes about 4,000 fish to make a ton of shell, which is usually worth £50, and the collection from stock would not cost a tithe of the present method of fishing and diving in open seas.

No doubt, excellent advice on the best methods of breeding up are avail able from those who studied this sub ject at Low Island, of whom Mr. Moor house is one. Perhaps, it will be a recognised industry of the future, and Barrier Reef allotments will be as high In value as banana land.