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, Ostrwa 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, Ostrwa 
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, 
