OYSTERS AND OYSTER FISHERIES OF QUEENSLAND. 269 



mud which lines the fissures." The author has been informed by a well-known Queensland 

 oyster-cultivator, that the same species of worm was noticed by him many years ago, burrowing in 

 the mud-filled crevices of timber-work in Sydney Harbour. The species, like most members of 

 its class, is an essential mud lover, and its natural instincts guide it, in its earliest larval condition, 

 to seek out and establish itself within any appropriate mud-lined crevice. 



So extensive have been the depredations of the mud disease with its associated worms in 

 New South Wales, that many of the formerly most productive oyster-grounds of that colony have 

 been practically depleted ; and it is owing to this disease, mainly, that, instead of exporting, that 

 colony is now so largely dependent on Queensland and New Zealand for its supplies. Much 

 anxiety has naturally been manifested to exclude this destructive agency from taking up its abode 

 in Queensland waters, and, having that circumstance in view, the fullest information concerning its 

 probable cause and possible prevention will doubtless prove acceptable. In this direction the 

 views expressed in a lecture upon " Oysters and Oyster Culture in Australia," delivered by the 

 author at the meeting of the Australian Association for the Advancement of Science held at 

 Christchurch, New Zealand, in January, 1891, are herewith recapitulated. 



" The rock oyster, Ostrea glotnerata, affected by the disease, is a species that attains to its 

 maximum development in brackish water, and indeed survives exposure to fresh water immersions, 

 in times of floods that would prove fatal to the so-called mud oyster, Ostrea ednlis. As a corollary 

 to the brackish water proclivities of Ostrea glomerata, its most luxurious development in New 

 South Wales has been high up the riverine estuaries, that so abundantly intersect the coast-line. 

 The Hunter, the Hawkesbury, and the Clarence rivers may be mentioned, not only as the most 

 important of the oyster-growing areas, but also as those in which the worm disease, or, as it may 

 be more correctly termed, the ' mud disease,' has been most prevalent. In my opinion, it is the 

 altered conditions of these rivers, brought about mainly through human agency, that has induced 

 the diseased condition of the oysters, their waters, in fact, being rendered more or less incapable 

 of supporting the mollusc in a healthy state. 



"Through the clearance of the land and the establishment of townships and settlements 

 throughout the watersheds of these rivers, the rainfall which in former days fell upon, and was 

 more completely absorbed by, the primeval forests, is now carried quickly away, and emptied by 

 drains and culverts into the watercourses communicating with the rivers. Simultaneously with 

 this augmented discharge of water into the rivers, a vastly larger quantity of sediment is brought 

 down, accompanied by a considerable percentage of organic and chemical pollution, that had no 

 place in the composition of the water under those conditions in which the oysters originally grew 

 and flourished. This greatly augmented accession of flood water, with its accompaniment of 

 sediment and chemical pollution, cannot exert other than a very deleterious influence upon the 

 riverine oyster fisheries. 



"A case in point, in which the oysters, formerly growing abundantly many miles up a river's 



