42 CEYLON PEARL OYSTER REPORT. 



Periya Paar. An examination of this remarkable region during the progress of the 

 fishery of 1904* showed the entire extent to be densely packed with untold millions 

 of young oysters from l to 3 months old. At the present time but a few handfuls 

 of these survive ; the others have, as usual, disappeared, having been no doubt swept 

 from the bank into deep water or buried in sand during the turmoil of the south-west 

 monsoon. Their place is, however, now taken by a new generation of young oysters 

 of the same age as those so plentiful upon the Cheval Paar. They will be of 

 excellent size for transplantation in March next, if there be then need of such an 

 operation. If not utilised they must inevitably share the usual fate of oysters on 

 this bank, and will without doubt disappear during the next south-west monsoon. 



ENEMIES OF THE PEARL OYSTER. 



Mr. HORNELL reports that " Oyster-eating fishes are at present abundant on the 

 banks. Numbers of 'Kilati' (Balistes mitis, chiefly) and' of 'Vellamm' (Lethriimx 

 nelndosiis and other species) were caught by the crew whenever we anchored upon 

 spat-covered ground, and unmistakable evidence of their diet was given by the 

 stomach contents. In the stomach of one Balistes which I examined there was found 

 a minute pearl." 



The quantity of young oysters is, however, sufficient to afford ample margin of 

 safety from such dangers, and with another 6 months' growth the shell will be 

 sufficiently strong to give protection against these particular enemies. " Greater 

 danger threatens from the huge ray called ' Walwadi tirikkai ' by the Tamil 

 fishermen (Rhinoptera javanica). This fish can destroy the strongest-shelled oyster, 

 and so great is its appetite and the capacity of its mouth and stomach that a 

 shoal is capable of destroying an entire bed of oysters within a few weeks or even 

 days, as witness the destruction of the fine bed of oysters on the Periya Paar Kerrai, 

 which was found to be in progress at the time of the fishery of 1903.t During the 

 recent inspection traces of widespread havoc from this cause were much in evidence 

 over the northern sections of the Cheval Paar, and this enemy is responsible for the 

 greater part of the reduction in numbers of the younger generation of oysters so 

 abundant on this area in March last." 



The region of the bank in question is notably deficient in natural cultch, and till 

 this defect is remedied this and other similar parts of the Cheval and Modragam 

 paars must always be more or less subject to ravages and losses, even to the extent 

 of occasional total destruction of a bed and the consequent failure of expected 

 fisheries. 



The boring sponge, Cliona margaritifera, DENDY, is doing great harm to the oysters 

 of the Modragam paars. On these banks there is also an excessive abundance of 



* See this volume, p. 28. 



t See this Report, Part II., p. 25. 



