246 THE NATURALIST IN AUSTRALIA. 



the present occasion. The same species of Rock Oyster is found, though not so 

 abundantly, up the Western Australian coast, and a considerable quantity are 

 systematically consigned from Shark's Bay and stations higher up the coast to Perth 

 and Fremantle. The species attains to the zenith of its development a little south of 

 the tropics, and on this account, other conditions being favourable, it grows to the 

 greatest perfection in Moreton and Wide Bays in Queensland, and their corresponding 

 parallels on the Western sea-board. The experiment has been initiated by the writer 

 of laying Rock Oysters down in the Swan River estuary at Fremantle. During the 

 writer's stay in the colony these oysters had increased in size and commenced to 

 propagate, though whether the species can be permanently acclimatised in a station 

 so far south of its natural habitat remains to be demonstrated. 



In prehistoric years the Swan River estuary was the site of enormous banks 

 of the ordinary cold water or Common Oyster, Ostrcea edulis, which, in the Australian 

 colonies, is most commonly known in contradistinction to the Rock species as the 

 "Mud" variety. Portions of the river bed are at the present date solid masses of 

 this oyster's shells, and similar accumulations on either side mark the former 

 much more considerable area of permanently salt water. With the process of time 

 the river channel and its connecting reaches have become more or less extensively silted 

 up, and so it has at length been brought about that where, formerly, water sufficiently 

 salt for the growth of oysters was permanently present, it has been, as now during flood 

 seasons, so Long replaced by that which is perfectly fresh that the oysters have been 

 destroyed. A somewhat similar process of oyster extermination by natural causes 

 was in course of actual operation in the Tamar estuary, Tasmania, some years since, 

 when the writer was investigating and reporting to the Government of that Colony on 

 the causes of the decadence of the local oyster fisheries and the prospects of 

 rehabilitating them. On this occasion, it being winter and the floods out, a crust 

 of ice had to be broken to obtain access to the few surviving bivalves. 



In Western Australia the most promising area for the establishment or 

 re-establishment of prolific oyster fisheries is, beyond doubt, in the vicinity of Albany 

 and King George's Sound. It formerly produced the so-called " mud " variety, Ostrava, 

 edulis, in great abundance, and there are even yet a few surviving from the reckless 

 depletion of the beds that was practised in years gone by. On the writer's advice, 

 Government oyster-breeding reserves are being established in the most suitable 

 locations in this vicinity, from which, in course of time, it is anticipated that 

 the former prolific beds may be again restocked. Denudation has, however, 



