OYSTERS AND OYSTER EISHERIES OF QUEENSLAND. 259 



some more scientific method than that hitherto in force will be in request, for saving some 

 portion of the vast amount of oyster spat annually produced, which, under present conditions, is 

 literally lost at sea. By the lowest estimate arrived at by trustworthy investigators, it would 

 appear that each mature female oyster produces at least from 2,000,000 to 3,000,000 embryos 

 at the annual breeding season. It has been further estimated by Mobius, concerning the 

 European species, Ostrca cdulis, that of the vast number thus produced less than one individual 

 in each of these million embryos runs the gauntlet of the innumerable perils that beset its 

 career, and arrives at maturity. The greatest amount of mortality that decimates this embryo 

 host is undoubtedly associated with their failure, after the maturation of their shells, to fall upon 

 ground or materials upon which they are able to effect an anchorage. Unless the surface on 

 which they fall is clean, and entirely free from slime or sediment, adhesion is not accomplished 

 and the embryo either drifts away or sinks into the mud, or sand, to perish. The aim of 

 the systematic methods of oyster culture in operation in European, and most notablv in 

 French, waters, is to encompass the salvage of the vast shoals of embryonic waifs that would 

 naturally run to waste. The accomplishment of this highly desirable object is effected mainly 

 through the provision of apparatus styled " collectors," that form attractive media for the adhesion 

 of the spat. These collectors are constructed ot varying form and material. From the earliest 

 days of oyster culture, the old shells, or " cultch," of the oysters originally raised for the market, 

 have been systematically saved and placed upon the beds with gratifying results ; such materials 

 constitute, in fact, one of the most natural media for the attachment of the embryo brood. 

 Faggots of wood, best known by their French title of " fascines," have been, and are still, 

 extensively used in French waters and at the ancient oyster-breeding establishment of Lake 

 Fusaro in Italy, for a similar purpose. The most efficient description of artificial spat collectors 

 that have been invented are, however, probably those first introduced into the French oyster- 

 grounds by M. Coste, which consist of a cheap form of earthen tile, the under surfaces of 

 which are coated with Portland cement. The calcareous constituents of the cement, when set 

 and seasoned, are so analogous to those of the parent oyster shells that the embryo brood adheres 

 to it with equal readiness. A second form of collector, successfully employed in France, con- 

 sists of cemented boards, united by their long edges in ridge-tile fashion, and strung one 

 above another in sets ; when anchored by a stone, they are allowed to float freely in the 

 current. This "ridge-tile" form of collector was employed by the author with fair results, 

 in connection with the Government Oyster Reserves of Tasmania, established under his super- 

 vision in the year 1885, with the object of resuscitating the (at the time) exhausted oyster 

 fisheries of that colony. Figures, with a description of this form of collector, were published 

 in the author's report to the Tasmanian Government for that year ; and, acting on the in- 

 formation therein contained, similar collectors were experimentally placed on one of the cultivated 



banks in Moreton Bay. These collectors were soon covered with spat ; but, being set in 



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