INTRODUCTION. ii 



The wire netting has been immersed in sea water and its durability tested. It was found to keep 

 intact and effective for a proved period of eighteen months, and thus wire netting would be suitable for 

 protecting spat for this period, after which time protection would not be so necessary. 



The principal cause of the failure, however, has been the non-occurrence of a spatfall during the 

 last few years. As no oysters were present on our own banks, it was obvious that if a spatfall did occur 

 it would have to be derived from elsewhere. It has long been beUeved that young oysters (larvae) travel 

 over to our banks from Southern India, where a few scattered and unproductive oyster beds occur. The 

 drift bottle experiment described in this Report proves that that is not only quite possible, but that it 

 certainly- does happen at times. Blank years on our own banks are due prmcipally to one of two causes, 

 either to the absence of oysters on the Tuticorin banks, or to tlie failure or sluggishness of the local 

 south-west monsoon current during the critical breeding time, which results in. the larvse failing to reach 

 tlie plateau, and, dropping into the abyss, being lost for ever. 



These facts, however, do not explain why it is that when once the banks have oysters on them 

 they should not be more or less independent of exotic spat, but maintain and develop their own. The 

 reason is simple, and is to be found in the rapaciousness of man, whose avarice kills the goose that lays 

 the golden egg, by omitting to leave breeding stocks ; also to voracious fish, to whom a bed of oysters is 

 a feeding ground, to be deserted for pastures new only when the supply is exhausted. So thoroughly have 

 the banks been devastated that during the last two and a half years less than half a dozen "shell fish " 

 (molluscs) have been obtamed, in spite of the efforts of divers and the use of the trawl and dredge. Thus it 

 is evident that other, and probably all, "shell fish " suffer equally with the pearl oyster, and it is only 

 on account of the commercial importance of the latter that the loss is noted. Now that the banks are 

 depleted of all molluscs, fish of all species are remarkably scanty; but one cannot doubt that, as in 

 past ages, when the banks do recover the fish will return. A fuller and more detailed account of the 

 ravages caused by fish will be found in Part IV. 



We thus come to agree with Steuart that in some respects the continuity of fisheries is dependent 

 on natural events which are beyond the control of man. But whilst this is so, we can almost escape this 

 catastrophe, and in any case extensively mitigate it, by reserving breeding stocks of old oysters in the 

 way indicated ; and, although even thus one could not hope to emulate the luxuriant bounty of Nature, 

 such breeding stocks would at least make the enterprise a successful one commercially. 



The importance and significance of trawling, dredging, and transplanting were fully dealt with in 

 Part V. Report, and need not be further considered here. 



In the present Report the subject of currents is extensively dealt with. The importance of the 

 surface currents prevalent during the spattmg season, and their relation to the natural distribution of 

 oyster larvae, cannot be exaggerated. Assuming oysters are present on the Tuticorin side, a spatfall on 

 our own banks is certain if the south-west monsoon continues strong at the critical breeding time. If 

 the monsoon is weak or erratic, then the larvae either di-ift through Paumben Pass, or drop into the 

 abyss on their way to the pearl banks, depending, of coiu'se, on the topographical position of the larva? 

 wlien the fluctuations of the monsoon begin. It is very noteworthy that the facts which have been 

 obtained fully and naturally explain why our banks usually retam their own spat as well as receive 

 exotic deposits, whilst the Tuticorin banks and those banks still under Government control are not only 

 destined to lose their own spat, but are situated in such a way that exotic falls of spat thereon are 

 almost physically impossible. These facts are amply borne out in the history of the areas concerned. 



Considerable misapprehension has existed during past years m relation to currents in genera! 

 over the banks. If a bed of oysters has disappeared, the cause has been attributed to currents, no other 

 explanation being obvious. Not only so, but the distinction between a top and a bottom current has 

 not been appreciated. A strong drift may be present on the surface of the water, which is not felt at 

 tlie bottom. Our experience, extending as it does over five years, has furnished no indication what - 

 ever of a bottom current, even though we have had access to the diving dress as well as the information 

 afforded by skin divers. We are of opinion that bottom currents do not exist, and that the loss of beds 

 of oysters in past years was probably never due to this cause, nor to silting over by sand. 



