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.
PEARL FISHERIES
The pearl fisheries of the Red Sea are at Lohia. At the lower end of the Red Sea, at Massawa on the African side, and at Lohia on the Arabian side, are a number of small barren islands; the banks lie in shallow water between them. The industry is financed by merchants, principally natives of Bombay, India, who in partnership with the Bedouin boat-owners, control the fishing. The Bedouin captain takes with him a few Arabs to man the boat and a number of black slaves as divers. The shells have a market value for mother-of-pearl but the quality is inferior. They have a greenish-gray edge and are fairly heavy and formerly they were much in demand.
Of late years the fresh-water unio shells have replaced them to a certain extent for cheap material but the shells are yet about ninety per cent. of the value of the fishings. Returns show exports of pearls averaging one hundred thousand dollars per annum but as a large number go direct to Bombay and are not reported, this does not fairly represent the extent of the industry.
The beds vary in depth, thirty to forty feet being the maximum depth fished. Naked native diving is the rule, but the Italian government has lately farmed out concessions at Dahlak and Farsan where they are experimenting with helmets. The fishing season is from the beginning of March to the end of May.
The arm of the Arabian sea lying between Arabia and Persia known as the Persian Gulf, has always been rich in pearl oysters and is a prolific source of supply to-day. These banks are fished chiefly for the pearls. The shell, though larger than the Ceylon, is of the "Lingah" class as it is called, and is of little value for mother-of-pearl.
Though pearl oysters are found all along the coast of Arabia, the most productive shoals are between the Islands of Halool and Katar. These shoals commence at the Island of Bahrein immediately off the Arab coast near the centre of the gulf and continue east and south along the district of Katar for nearly two hundred miles after which the banks are lost in deep water. The chief centre of the pearl trade is Lingah, hence the name given to the shells of this district. Most of the pearls go to Bombay and are known as Bombay pearls, many of them having a distinctly yellow tint. The whitest and finest go to Bagdad and eventually the best go to Europe. India takes the irregular ones and China gets the seed-pearls.
The principal banks are at Bahrein. This island is the most important one of a group situated in an indentation of the Arabian coast and is about seventy miles long and twenty-five broad.