Page 71 - Records of Bahrain (3) (ii)_Neat

The pre-war economy: pearl fishing, 1899-1915 487

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this rule be correct, the majority of the bivalves brought to the surface
by divers in the Persian Gulf arc over two years of age, and a large
number arc over three years.
The movements of the oyster arc entirely uncertain, defying forecast »
thus in the season of 1870 nearly every pearl boat in the Gulf was riding
in the vicinity of the Shah Alum shoal and a magnificent haul of oy6tcr6
was obtained in a very restricted area, while in the following 37ear the same
locality—contrary to the expectations of the divers—proved almost barren.
It i6 known that in the Gulf the oysters sometimes suffer severely from
submarine disturbances, accompanied by the emission of gases and bitu­
minous products; this was notably the casein 1900, when the sea iu
places on the Arab banks was reddish and turbid and the oysters on some
of the beds were found to be dead or diseased and produced no pearls.
The notion that the Arabs feed the oyster beds at certain seasons of
the year is erroneous; nor is the oyster itself often eaten, except by the
natives of Trucial 'Oman.

Persian Gulf Pearls.

The classical word for a pearl in Arabic is Lulujjy (plural, Laali
and in Persian Marwarld ; but the term iu common use all over
the Persian Gulf is Qumashah (plural, Qumash ).
byssus is formed of material accreted by a special gland and the foot is used to bring
each strand, ns it ie moulded or cast, into contact with the point selected for
fixation. The byssus hardens on oontact with sea water, and its colour changes
within 48 hours from a palo almost transparent yellow to nn opaqae and lustrous
bronze-green. The animal can at any timo let go the iuner end of the byssus
whore tho strands aro fused into one, and it frequently does so when it is nnnblo to
find a placo with which it is thoroughly satisfied ; a specimen under observation at
Gallo changed its position'7 times and formed a byssus no less than 8 times in a
fortnight, tho byssus on ono occasion consisting of 9 strands. The adult oyster is
very sensitive to light nnd shade, and will closo up even in a depth of 9 fathoms in
consequence of a shadow passing over tho surface of the sea ; its movements, probably
from fear of predaceous animals, aro mostly performed during tho hours of darkness,
and are discontinued if an artificial light is brought t^ bear.
The animal can rolease itself from a covering of sand not exceeding 1£ inches,
but, if buried to a depth of 3 inches, it is helpless and dies. Tho shifting of sand,
caused by monsoon or storm currents, is undoubtedly tho oauso of many disasters to
oyster colonies, aud it was probably an important factor iu tho total disappearance
from tho Periya Pnnr in Ceylon, betwocn March and November 1902, of a uuiubor of
young oysters computed at no less than a bundled thousand millious. *
Tho principal enemies of the oyster are voracious fishes, chiefly rays and file-
fishes, tho former of which can apparently orush tho shell of the adult oyster with
their teeth ; boring gastropod mollusca ; boring sponges, which sometimes honeycomb
tho slndl of tho adult oyster so rendering it an easier proy for fish; boring worms ;
starfishes; lamellibranch mollusca, which smother tho animal; crabs and cultlo-
fishes ; and, finally, associated animals such as corals, barnacles aud sponges, which
adhero to tho shell and, mechanically or by competition for food, cause injury and
evon death.
Othor causes of mortality among oysters are ovarorowding, which interferes with
nutrition and growth ; also, possibly, the opposite evil of over-fishing by which tho
stool; left for breeding may bo too greatly roducod.' Diseasos duo to parasites but
probably opidemic and assisted by overcrowding, also claim many victims.
a