Dec. 1, 1900.] THE TROPICAL AGRICULTURIST. 
393 
neighbourhood. The cliff opposite the " Doric" 
is grailuiliY washing away, and much oi the 
island of Karraittivu has disappeared since I first 
knew it. On the other liand the spit foimitifr 
the western side of Dutch Bay has been extended 
into the sea in a K.E. direction about one mile 
durin]L( the last, 40 years. 
ENEMIES OF THE PEARL OYSTER AND 
CURRENTS. 
The enemies of the Pearl Oyster are no doubt 
many, as it seems t'.> b*- the nature of all animal 
life in the sea, to prey upon each other ; but the 
chief ones to be feared and destroyed, if possible, 
are the various species of fish that feed on the 
bottom, and for that reason are commonly called 
rock fish. Thtse, with tlie exception of skate are, 
however, only destructive to the pearl oysters 
when they are young and their shells tender ;say 
up to the age of 18 months or 2 years, after which 
age the smaller kinds of rook fish, which appear 
to be most numerous do not do much harm. 
Generally speaking, when I have been at anchor 
on a be i of young oystersj the crew of the vessel 
have caught many rock rish, the stomachs of which 
were found to contain many fragments of the 
young oyster shells, thus proving the source of 
their food. 
A bed of young oysters no doubt attracts these 
rock fish, which appear to come on it in great 
swarms, and although the young oysters are very 
numerous, and are generally very thickly spread 
over large areas, I have counted as many as 40 
attached to the fragment of an old oyster shell, 
yet their enemies are numerous also, and are 
capable of causing much destruction, often com- 
pletely annihilating the whole bed, leaving not a 
vestige behind when I visit the bank a year later ; 
so that if some means cotild be devised of destroy- 
ing or keeping these rock fish away from a bank 
of young oysters for a couple of years, there would 
undoubtedly be more Pearl Fisheries. If, for in 
stance, fishermen could be induced to take say 200 
canoes to one of these beds of young oysters, and 
fish on it daily for 2 or 3 months, it would have 
a very good eti'ect, and might possibly cause the 
dispersion of the fish which readily take bait, 
and the numbers likely to be caught would well 
reward the fishermen. 
Currents must also be classified amongst the 
enemies of the pearl oyster, for although they 
bring the spat on to the oyster beds, they also 
occasionally sweep mature oysters away from 
the be s. 
The most noteworthy current on record is that 
which in December, 1887 swept away a very 
valuable bed of oysters, estimated at 155 millions, 
from the Cheval Paar. Ten millions of them were 
found during the fishery in the following March, 
from two to three miles in a S. -easterly direction 
from their original position. Attributing this to 
a current I enquired of the man in cliarge of 
the steam tug "Active" doing guard duty on the 
Cheval Paar at the time, and he reported that in 
the middle of December there was a strong 
current lasting a ^^eek, running in a southerly 
direction, and was so strong, about 4 knots, that 
he had to drop a second anchor to prevent the 
vessel being dragged away by it. The fishermen 
on Kariaittivu island subsequently confirmed the 
existence of a strong southerly current running 
in December. 
The loss of that bed of oysters was a loss to 
Government of^at least 20 lakhs of rupees. 
On this occasion I was able to make an in- 
teresting experiment as to the ability of pearl 
oysters to re.--ist a current. The divers had brought 
up a laige Pinna shell with several oysters attach- 
ed to it by their byssus. The "Active" was got 
underway and the Pinna shell towed in the sea 
alongside. The oysters held on for an hour, while 
the "Active" was going at a speed of 4 knots, 
but when the speed was increased to 5 knots they 
shortly began to drop oif one by one. Although 
the oysters lesisted a 4 knot current for one hour, 
they evidently had to give way when the strain 
of a current of that velocity was prolonged for a 
week. I doubt very much their ability to resist 
evec a 3-knot current tor that length of time. 
Young oysters have a much stronger hold 
than oysters advancing to maturity. The divers 
otten remark when on young oysters, that 
they could not bring up many, as they were 
holding on fast ; but when they come away easily 
the divers say they are fit for fishing. 
There is no record of a current similar to that 
of December, 1887, having occurred previously 
andl look upon that one as very exceptional, parti- 
cularly as to its course which was in a S. -easterly 
direction. 
I am of opinion that it was caused by an 
unusually large volume of the N.E. Monsoon 
ocean current fiowins into the Gulf of Mannar, 
and seeking an outlet by sweeping round the 
head of the Gulf, and down its eastern shore, 
until it joined the main stream, on its course 
from the coast of Ceylon towards Cape Oomorin. 
It is well-known that the current from the Bay 
of Bengal in November and December, runs 
south along the east coast of Ceylon at the rate 
of 2 to 3 knots an hour. It curves round the 
south coast, and after rounding Galle, takes 
a N. -westerly course past Cape Comorin. Some 
times it follows the west coast of Ceylon to the 
north of Kegombo, and t hen branches ott' towards 
Cape Comorin. A larger volume than usual 
coming this way would probably advance further 
up the coast than Negombo, say to Chilaw and 
then branch off towards Cape Comorin, and in that 
case some portion of the stream might before 
reaching Cape Comorin be deflected along the 
Tuticorin shore and then follow the course I 
have described. I cannot account for a S.E. 
current on the Cheval Paar in December in any 
other way. 
There are also unknown enemies of the pearl 
oyster. For instance when oysters too young 
for fishing are found dying off in large numbers, 
it has not yet been discovered what causes them 
occasionally to be in that condition. 
The question of discovering means of success' 
fully securing pearl oysters against their enemies 
is a most difficult one to solve. Currents are 
uncontrollable, and as regards living and un- 
known enemies, success against their predations 
appears to me to be very doubtful. Yet ia 
these ■wonderful progressive times there is no 
knowing what the employment of scientific skill 
to deal with these questions might be able to 
accomplish. 
ARTIPIOAL CULTIVATION OP PEARL OYSTERS, 
I have tried a small experiment in cultivating 
Pearl Oysters, by depositing a quantity of young 
oysters in an excavation which I had made for 
tliem in the Sillavaturai coral reef, three niileii 
from the shore ; but Jt was not succes^fv^j, 
