12 PEARLS AND PARASITES 



man reported to the Government of Ceylon as 

 follows : 



' The oysters we met with seemed, on the whole, to be very 

 healthy. There is no evidence of any epidemic or of much 

 disease of any kind. A considerable number of parasites, both 

 external and internal, both protozoan and vermean, were met 

 with ; but that is not unusual in molluscs, and we do not 

 regard it as affecting seriously the oyster population. 



' Many of the larger oysters were reproducing actively. We 

 found large quantities of minute " spat " in several places. 

 We also found enormous quantities of young oysters a few 

 months old on many of the paars. On the Periya paar the 

 number of these probably amounted to over a hundred 

 thousand million. 



' A very large number of these young oysters never arrive at 

 maturity. There are several causes for this. They have many 

 natural enemies, some of which we have determined. Some 

 are smothered in sand. Some grounds are much more suitable 

 than others for feeding the young oysters, and so conducing 

 to life and growth. Probably the majority are killed by 

 overcrowding. 



' They should therefore be thinned out and transplanted. 

 This can be easily and speedily done, on a large scale, by 

 dredging from a steamer at the proper time of the year, when 

 the young oysters are at the best age for transplanting. 



' Finally, there is no reason for any despondency in regard 

 to the future of the pearl-oyster fisheries if they are treated 

 scientifically. The adult oysters are plentiful on some of the 

 paars, and seem for the most part healthy and vigorous ; while 

 young oysters in their first year, and masses of minute spat 

 just deposited, are very abundant in many places.' 



The chief causes of the failure of the fisheries, at 

 any rate the chief causes which can be dealt with by 

 man, are overcrowding and over-fishing. It might 

 be supposed that these factors would counteract each 

 other ; but it must be remembered that they become 

 effective at the two opposite poles of the oyster's 

 existence, which is thought to cover five, six, or seven 

 years. The overcrowding takes place when the 



