FISHING FOR PEARLS.
Pearls differ from any other kind of precious gems in requiring no aid from art to bring out their beauty. While diamonds and sapphires and rubies require to be cut and polished before they flash forth their lustrous light, pearls may be said to be ready-made wherever they are found.
Those who wear and admire them probably give little thought to the circumstances attending their production and collection; but there are few industries more interesting than that of ‘fishing’ for pearls, as practised in the most important pearl-producing districts. Pearls of an inferior quality to that of the true Oriental are found in a species of fresh-water mussel inhabiting Britain and other temperate countries: an important field for their production is being developed on the coasts of Queensland and Western Australia; and at the Cape of Good Hope specimens are occasionally found. But the great centres of the industry are the banks around the south and west coasts of the island of Ceylon, from which districts all the most celebrated pearls have been derived. The banks or paars there are under government supervision, and fishing is only allowed under the immediate inspection of the officials, who issue stringent regulations on the subject.
For some years the produce of the paars has been falling off, and a series of experiments has recently been carried out, and is now in course of completion, with the object of discovering whether, instead of allowing them to be fished every year, an interval of one, two, or three years between each season will not afford a better opportunity to the bivalves to spat and develop into pearl-bearers.
The last great fishing took place during the month of March in 1877; and, as the results are said to have exceeded those of any previous season for many years past, a short account of the manner in which the operations were carried out, together with a review of the system adopted for protecting the beds from exhaustion, may be interesting.
In the first place, it will be well to remove a misapprehension which exists as to the identity of the so-called pearl-‘oyster.’ This mollusc is not an oyster properly so called, but a species of mussel, and is easily distinguished from an oyster by the squareness and length of the shells at the ‘hinge.’ Like the common mussel of our own shores, it attaches itself to stones and rocks by means of certain fine but strong cords or byssus, which it spins at will; and not, like the oyster, by a secretion of shell-matter. These cords are very tough when the animal is young, but decrease in strength as it increases in age, till at last they rot away altogether, leaving the creature at the mercy of tides and storms.
While the pearl-oyster is still young, and before it has finally attached itself to a suitable rock, it often breaks away from its anchorage; so that it not unfrequently happens that a pearl-bank well filled with oysters suddenly disappears altogether. Some authorities assert that the pearl-oyster has the faculty of casting its byssus and voluntarily migrating; but whether this is the fact or not, it is certain that the above circumstances demand the serious attention of the authorities, and have led to the adoption of a system of half-yearly inspection of the banks, in order to determine two important points, namely whether the young brood has forsaken its birthplace, or the full-grown oysters are, through old age, breaking away and being destroyed.
The duration of the life of the oyster is another necessary point to determine; and various suggestions have been made, with the double object of ascertaining the age of an oyster without the necessity of continually watching its growth, and of shewing when a bed is fit to be fished. The weight of the mollusc affords some clue to the elucidation of this problem, but there is an obstacle to the adoption of this method in the difficulty of accurately weighing a number of specimens in an open boat at sea, even if the scales and weights should be at hand. One of the government officials, however, has suggested a method of ascertaining the age of the mollusc by the weight of the shells, cleaned and dried with the animal removed. This can be done at any time; and a series of experiments conducted by him gives the following results. The shells of an oyster one year old, with the body of the animal removed, weigh four drachms; those of an oyster two years old weigh twelve drachms; three years old, nineteen drachms; and four years old, twenty-five drachms. This scale of weights will apply of course only to pearl-oysters from the Ceylon banks; as a difference in the food, in the composition of the water and soil, and the temperature in other parts of the world, would no doubt affect the rate of growth and the deposit of the calcareous matter forming the shell. Empty shells have been found weighing as much as forty drachms, thus giving a probable age of about eight years.
The question arises, What are pearls? Are they a morbid concretion of matter produced in the endeavour to heal a wound or to cover some irritating body that cannot easily be ejected from the shells? Are they the result of a disease, or are they simply an over-production of the matter forming the shell of the creature? Whatever they are, it is only in the adult oyster that they are found of any size. The rate of growth in the size of a pearl cannot of course be actually ascertained; but by a series of averages, taken from the produce of a large number of oysters from the same bed in different years, it is proved that after the fourth year, the yield of pearls both in quantity and quality rapidly increases. It is in the hope of a bed of oysters which produces say five hundred rupees’ (L.50) worth of pearls per thousand oysters one year, so improving as to yield double that value next year, that many a fine bank has been left to perish from the causes referred to above, as well as from the attacks of enemies or sickness.