HABITAT OF THE PEARL OYSTER
The Pearl Oyster is found in more or less abundance on the shoals and reefs about the shores of every land within a belt of the earth lying between 30 degrees north and south of the equator. Coral reefs and limestone foundations usually form the beds on which they propagate. Beyond these limits the abalone is found at Japan, on the California coast, Queen Charlotte's Island, the Cape, Australia, New Zealand, China, about the English Channel, and on the coast of France, where the shores are washed by equatorial currents. It exists also on the shores of India and the Canary Islands.
The largest and heaviest shells, which yield fine mother-of-pearl most abundantly are confined almost entirely to the Pacific Ocean within twenty degrees south of the equator. The best white shells come from the northern shores of Australia and the Aroo islands. The best black shells are found about Tahiti, the Gambier Islands, and the Tuamotu Archipelago. Of the big yellow variety, the best are obtained in the Merguian Archipelago and Dutch Indies. The shells of this district at Ceram, Batjan, and elsewhere, vary somewhat but the bulk of them are yellow.
Beginning with the east coast of Africa, the pearl oyster is found in the Red Sea, where it has been fished for ages. The shell here is of medium size and weight; much larger than those of Venezuela, Ceylon, or the Persian Gulf and smaller than the shells of the Pacific. The mother-of-pearl is not of the finest quality and is used now for inferior work only. It was more used formerly but since the fresh-water unio shell of the United States came into the market, it has displaced to a great degree the Egyptian and Panama shells. The inner edge of the Red Sea shell is of a greenish-gray color.
South of the Red Sea, on the East of the African coast, pearl oysters are found in a number of places between Zanzibar and Inhambane, particularly at the Bazaruto Islands, but nowhere in sufficient abundance to develop the fishing for them into a regular industry. Good mother-of-pearl is abundant on the German East African coast, but the oysters carry few pearls.
Travelling east, they are next found in large numbers in that arm of the Arabian Sea known as the Persian Gulf. Here they have existed for many centuries. The mollusk is of the smaller species and the shells are known in the market as Lingahs, from the name of the centre of the pearl trade in this district. The shells are of no commercial importance.
After these come the ancient fisheries of India, the most prolific in the world. The oysters here are smaller than those of the Arabian Sea and the shells are of no value, but they mature rapidly and yield great quantities of pearls. Myriads of them cover the shoals and banks between the coast of India, at the South-eastern point, and Ceylon, and as the beds are under government supervision, they cannot be destroyed by the reckless fishing of immature oysters.
Crossing the Bay of Bengal and the Malay Peninsula, between longitudes 100 and 120 degrees E., there are pearl oysters on the coasts of China, the Merguian Archipelago and western Australia. Between longitudes 120 degrees E. and 150 degrees E., these mollusks flourish on many coasts, including those of Japan, the Sulu Archipelago, the Dutch Indies, the Spice Islands, the Banda Islands, the Aroo Islands, New Guinea and northern Australia.
The Australian shells are large and the lining is white and fine. As shell fisheries they are the largest in the world and although the value of the pearls found is small compared with the amount realized from the sale of the shells it is considerable and growing. The Aroo shells are white like the Australian. Those from the Banda Islands are a smaller black-edge shell. Most of the others like the Manila shell of the Sulu Islands, are yellow.
At longitude 165 degrees E. the fisheries of New Caledonia are becoming notable for the number of fine fancy colored pearls found there. Both avicula margaritifera and meleagrina margaritifera are taken off the west coast.
In the waters of the Fiji Islands, longitude 180 degrees E. pearl oysters of the black-edge shell variety similar to the Bandas but a little larger are fairly abundant.
Fine shells, often containing very beautiful pearls, are taken off the coasts of Tahiti, Gambier, and throughout the Tuamotu Archipelago, lying between longitudes 130 degrees W. and 150 degrees W. The shells are of the black-edge type, large and heavy. The nacre is thick and has a particularly mellow luster; throughout this section both shells and pearls rank among the best.
All over the South Sea, pearl oysters are found about the islands and in the lagoons within the atolls which stud it, but in quantities too small in many places to induce capital to establish fisheries. Fishing for them is confined therefore to native divers who are rewarded by the occasional find of a few pearls, which often they sell at ridiculous prices to the stray traders who may chance to come their way.
This eastward journey now brings us to the Pacific coast of the American continent. Here the pearl-bearing mollusk is found on the shores of Lower California, about the Islands of the Gulf of California, at various points on the Mexican coast-line south to Acapulco and at Panama. They exist also on the coast of Ecuador but of late years fishing has not proved remunerative and it is now carried on in a desultory way only. They are found also on the western coast of Nicaragua.
The Mexican shells known as Panama shell or bullock shell have a dark, dirty, greenish rim and are much less valuable than the white or black shell. Similarly, dark, slaty-colored pearls are known as Panamas because many pearls taken on this coast are of that character. This color tendency however often results more advantageously as many of the pearls are sufficiently dark to be classed as fancy and some beautiful black and red pearls are found in these waters. Panama pearls also have the reputation of being softer than others. There are pearl oysters also on the Peruvian coast but this section has not yet been fished.
On the Atlantic side of America pearl oysters are abundant in the Gulf of Campeche and on the shoals about the islands and shores of Venezuela. The shells of Central America are similar to the Panamas only more yellow, while those of Venezuela are small and valueless. Between the east coast of America and the Red Sea are no fisheries save at Haiti, for no discoveries of any importance have been made on the western coast of Africa.
Consideration of these homes of the pearl oyster shows it to be a tropical fish and that it attains greater dimensions in the Pacific Ocean and near the equator than elsewhere. Beyond 30 degrees north it is found only at two points, the western shore of America and on the Japanese coast. These shores are washed by equatorial currents. The small varieties of the Indian seas and Venezuela, mature rapidly in four to six years, and if not taken they die out after the seventh year. The meleagrina of the Pacific however, though it attains its full size in six to eight years, continues to lay on shell-nacre up to twelve and even twenty years. A shell which is of good size but comparatively thin is called by the dealers in mother-of-pearl a "young shell." The Australian pictured at page 129 is such an one. The Tuamotu at page 127 is not full grown but well along in years, probably fourteen to sixteen years old.
Of the sea mollusks yielding formations which, though not true pearls, are so called, (Strombus gigas), is a native of the West Indies. Another, a gasteropod, the ear-shell (Haliotis) known in the United States as the abalone, is found on the coasts of California, Japan, the English Channel Islands and elsewhere. The Californians are divided into three classes, the blue backs, about six inches long, and green and red-ears, which are half as large again. Pinnas yielding black seed-pearls are found south of the Island of Mafia on the east coast of Africa. On the banks and shoals between Mafia and Zanzibar is a red mussel from which white pearls are taken.
The fresh-water pearl-bearing mussel, the unio, unlike the sea oyster is most abundant north of 30 degrees N. In China and the Hawaiian Island Oahu it is found a little to the south of 30 degrees N., and it has been discovered lately in Southern Rhodesia a little north of 30 degrees S., but the countries and streams in which the unio is plentiful and where it yields the most pearls lie within latitudes 30 degrees N. and 60 degrees N. They have been taken from the streams of Great Britain since the times when the Romans had a colony here. They exist in Bohemia, Saxony, Bavaria, Lapland, Canada, Labrador and in great quantities in the United States.