FRESHWATER FISH EPIDEMiCS IN QUEENSLAND RIVERS. 181 



(mineralised) holes. All kinds of fish were affected and in each 

 case the disease shoAved the same symptoms — " a blue spot 

 on the side, upon the bursting of which the fish died." ]VIr. 

 Ogilbj' subsequenth' suj^plied information to the Press that 

 Saprohgnia would not live in water which contained any 

 degree of salinity, as was the case with the " kopai " holes. 



Mr. Caldwell informed us that the epidemic had appeared 

 in November 1917 and June and July 1918, in the upper 

 reaches of the Georgina, in the vicinity of Lake Xash. Tons 

 of dead fish were to be seen and plenty of sick fish v.ere being 

 caught near the surface and along the edge of the lake by 

 aboriginals. The species represented were yeUow-beUies, 

 catfish (jewfish), bony bream, and another kind. The stretch 

 of water in A^hich the mortality occurred was five or six miles 

 long and in places between 20 and 30 feet in depth. Commonl}' 

 associated A\"ith the disease was the presence on attacked fish 

 of a bluish swelling about the size of a sixpence or shilling, 

 at the side in the abdominal region, the aboriginals stating 

 that when these " boils " burst the fish turn over and die. 

 In " kopai " holes the water was clear and brackish oA^ing to 

 abundance of calcium sulphate (" kopai ") and the fish were 

 normal. A\'hereas in the adjacent waterholes containing clayey 

 or muddy v.ater, even though somewhat brackish, the fish 

 Avere d^ang. This happened between May and September 

 1918 wliile Mr. Caldwell was on the Georgina. There was no 

 drought at the time and cattle were fat. 



Mr. Caldwell also stated that in large waterholes in the 

 Austral Downs district (Northern Territory) near Camooweal, 

 though fish Avere plentiful, no dead ones were seen b}^ him during 

 his vi.sit in May 1918. 



In subsequent communications (October and November 

 1919) he informed us that attacked fish came to the surface and 

 were very sluggish in their movements. An old aboriginal had 

 informed him that fish had died periodically in the Georgina 

 River as long as he could remember. Mr. Caldwell stated 

 that one vieAv as to the cause was that it was due t^ over- 

 stocldng and consequent shortage of food ; another, that it was 

 due to cold weather, or to the prevalence of "umbrella grass" 

 which blocked up the gills of the fish. Cormorants were 

 especialh" abundant, and these, together with the large 

 numbers of pehcans present, were in his opinion sufficient to 

 prevent any overstocking. 



