May 17, 1906] 



NATURE 



57 



illE I'EAHL FISHERIES UF CEYLON.' 



""pHIC important scries of reports on the pearl-oyster 

 -'■ fislicries and on the marine biology of Ceylon, 

 prepared under the direction of Prof. Ilerdman, which 

 is beinj,' published by the Royal Society at the request 

 of the Colonial (jovernmcnt, continues to grow both 

 in size and value. Parts iii. and iv. have been recently 

 issued, and although in the preface to part iii. Prof. 

 Herdman expresses the hope that the whole will be 

 completed in four parts, this has not proved possible, 

 and a fifth part is now contemplated, to contain the 

 concluding sections of the pearl-oyster work, several 

 more supplementary reports of a faunistic character, 

 and a general discussion of the faunistic results. 



The two parts of the pearl-oyster report now under 

 review give a summary of the results of the more 

 recent investigations and inspections carried out by 

 .Mr. Hornell on the banks in the Gulf of Manaar, 

 together with an account of the pearl fishery of 1905, 

 wiiich proved to be far in excess of any recorded fishery, 

 both in the number of men and boats engaged, and in 

 the quantity and value of the oysters taken, the 

 nearest approach to it 

 bi'ing the fishery of the 

 previous year, 1904. 



Prof. Herdman and Mr. 

 Hornell have been exceed- 

 ingly fortunate in being 

 able, so soon after the 

 commencement of their in- 

 vestigations, to study the 

 exact conditions under 

 which these two most 

 successful fisheries have 

 been carried out, and 

 although they state that it 

 does not seem likely that 

 the 1905; results will be 

 rivalled by any prospective 

 fishery of the oysters now 

 in sight upon the grounds, 

 yet the knowledge and in- 

 sight into the nature of tin- 

 factors leadin.g to a great 

 and profitable fishery which 

 have been obtained will be 

 of the very highest value in 

 suggesting rational meas- 

 ures for the future control 



and improvement of the beds ; and a careful perusal of 

 Prof. Herdman 's reports leaves little doubt that in the 

 case of these pearl-oyster beds, practical measures 

 carried out upon a sufficiently large scale under ade- 

 quate scientific control will be capable of effectively 

 preventing, in most years, such total failures of the 

 fishery as have been so often recorded in the past, and 

 of ensuring to those engaged in the work a much 

 more certain and uniform return for the labour and 

 capital employed. 



The investigations already made show clearlv that 

 the different beds or " paars " are subject to very 

 different conditions, and whilst some, which are 

 specially favourable for the growth and development of 

 the oysters, are liable to receive only a small and inade- 

 quate fall of " spat," others almost invariablv become 

 covered at the breeding season with an abundant supply 

 of the young brood. Since, however, the latter beds 

 are situated further seawards and close to the deeper 



water, the young brood is frequently, if not generally, 

 destroyed by the action of currents or by bemg over- 

 whelmed by sand, so that the oysters never attain 

 maturity. These circumstances naturally suggest that 

 the transplantation of young brood oysters in large 

 quantities from the outer exposed beds to the inner 

 ones, which are favourable for their growth and de- 

 velopment, will be a highly profitable operation in 

 those years when the inner beds do not receive a 

 natural fall of spat. Such transplantation constitutes 

 one of the principal recommendations which Prof. 

 Herdman and Mr. Hornell make for the develop- 

 ment of the fishery, and work on these lines has 

 already been commenced, although in 1905 it was 

 not particularly called for, excepting on the grounds 

 actually cleared during the fishing of the year, owing 

 to a very extensive natural fall of spat on all the 

 beds which had taken place in the autumn of 1904. 



Other practical measures which are recommended 

 include " cultching," or the deposit of suitable solid 

 material, such as shells or broken stone, to which the 

 voung ovsters can attach themselves._ the thinning out 

 of overcrowded beds, and llic cleaning of the oyster 



1 " Report to the Go\ 

 the Gulf of Manaar." 

 mentary Reports upon t 

 Part Hi., pp. viii+328 i 

 (Published at the reque> 

 London. 1905.) 



irninent of Cevlon on the Pearl-Oyster Fisheries of 

 By Prof. W. A. Herdman, F.R.S. With Supple- 

 le Marine Biology of Ceylon by other Naturalists, 

 nd plates; and part iv., pp. xvi + 242 and plates, 

 of the Colonial Government by the Royal Society, 



1 the Pearl Oyster Fisheri 



banks by means of the dredge, thereby removing in 

 as large numbers as possible such enemies of the 

 oysters as starfishes, and also other animals which 

 would compete with the oysters for the available 

 supply of food. 



If we may venture upon a word of suggestion, we 

 would express a hope that in the concluding volume 

 Prof. Herdman will furnish us with a concise and 

 sufficient summary of the whole of the pearl-oyster 

 reports, since from the nature of the circumstances 

 in which the series has been produced it is a little 

 difficult to extract from them the essential features of 

 the valuable work accomplished. We wander along 

 pleasantly enough with Prof. Herdman on his explor- 

 ations in the Gulf of Manaar, and accompany Mr. 

 Hornell with pleasure during his inspections of the 

 pearl banks from year to year ; we traverse many an 

 agreeable bv-way under Mr. Hornell's direction, and 

 not infrequentlv retrace our steps along the same paths 

 with Prof. Herdman for our guide ; we are allowed to 

 see, as it were, the ideas gradually developing in the 

 ininds of the two investigators, and we watch with 

 interest the new facts and suggestions of Mr. 

 Hornell's various letters and reports becoming gradu- 



NO. 1907, VOL. 74] 



