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A BACTERIAL DISEASE DESTRUCTIVE TO FISH IN 

 QUEENSLAND RIVERS. 



By Professor T. Harvey Johnston, M.A., D.Sc, University of Adelaide, and 

 Leith Hitchcock, Commonwealth Prickly Pear Laboratory, Brisbane. 



[Read June 14, 1923.] 



From time to time a very widespread and serious mortality has made its 

 appearance amongst fresh water fish in localities extending from Anthony 

 Lagoon, in the Northern Territory, to the Georgina River and Cooper Creek, 

 together with their affluents, as well as the Queensland tributaries of the Darling 

 basin, besides certain rivers entering the Gulf of Carpentaria and the Pacific 

 coast of Queensland. 



The senior author published a preliminary report in 1917, but the material 

 submitted for examination, and on which the paper was based, was very scanty. 

 In 1921, in conjunction with Mr. J. Bancroft, the result of a much more extended 

 inquiry was made known. 



The inaccessibility of the localities in which epidemics were reported to be 

 in progress, and commonly the tardy arrival of information regarding their 

 occurrence, seriously handicapped the investigation ; consequently no observa- 

 tions Vv^ere made during an epidemic, though on one occasion a visit was made 

 to a locality within a few days of its disappearance. 



The outstanding features of the epidemics according to newspaper reports 

 as well as information received from many infected localities, were as follow : — 

 (1) Certain species were specially afifected, e.g., Serranid perches (Plectroplites 

 ambiguiis, Richdsn. ; Therapon spp. ; Oligorus macquariensis, C. & V.) ; 

 Clupeidae (Nematalosa sp.) ; and Catfishes (Plotosidae). (2) The epidemics 

 occurred nearly always in the colder and drier part of the year (July and August), 

 and in almost all cases the water was stagnant. (3) They ceased suddenly 

 after rain had caused the streams and rivers to flow. (4) Affected fish were 

 generally very fat, and death appeared to be due to an asphyxiation. 



From the available evidence it appeared that the condition was not due 

 directly to any of the following causes : — Dry weather ; low temperature ; over- 

 stocking of the waterholes representing the shrunken rivers and creeks ; helminth 

 or protozoal parasites. Though the fungus Saprolegnia was found commonly 

 associated, it was regarded as being an organism which aggravated rather than 

 caused the condition, and it was suggested that the epidemic was primarily due 

 to the presence of some virulent bacterium whose multiplication and dissemina- 

 tion were favoured by a high acidity of the water, due to excess of carbon 

 dioxide ; in other words, by stagnant conditions. Though abundant bacteria 

 were found in dead material in the Thomson River on the occasion of a visit, 

 no cultures were made from the putrescent fish on account of lack of suitable 

 facilities for carrying on bacteriological work at the time. 



In these papers (1917, 1921) reference was made to the occurrence of 

 dead fish floating down the lower Brisbane River during August and September, 

 1917-1918, and it was mentioned that the opinion of J. D. Ogilby, ichthyologist 

 to the Queensland Museum, was that the use of dynamite by boating parties 

 higher up the river was responsible for such mortality. Such a view was 

 strengthened by an examination of a specimen submitted by that Museum, the 

 disorganization of the viscera being such as would be caused by an explosion. 

 On account of this, the Brisbane River epidemics were ruled out from further 



