BY T. HARVEY JOHNSTON. 131 



water. The use of permanganate vmder such circum- 

 stances is condemned. 



The above information may be of some use in the case 

 of aquaria and fish hatcheries but is not applicable to the 

 Queensland conditions where large expanses of water in 

 widely distributed areas are concerned. Where the town 

 water supplies are affected, little can be done beyond 

 removing any dead and dying fish that can be reached — 

 also any surplus vegetation. This may perhaps be done 

 by netting. The boiling of such water before use is of 

 course advisable. 



The state of affairs existing in the late winter wa« due 

 no doubt to the long period of dry weather restricting the 

 flow of the rivers and converting them into a chain of water- 

 holes. Thus stagnant conditions prevailed, leading to 

 unhealth}- environment for the fish, causing weakness and 

 thereby giving Saprolegnia an opportunity to exchange a 

 saprophytic existence for a parasitic mode of life. The death 

 of numbers of fish would increase the amount of organic 

 pollution and deplete the oxygen sui3ply owing to the 

 presence of abundant saprophjrtic bacteria and fungi, thus 

 still further aggravating the position. The arrival of the 

 rainy season should soon remedy the trouble as the rivers 

 will be set in motion, aeration will be improved, and the 

 surroundings become again suitable for healthy fish life. 



Since the above was written, Mr. C. Booker, M.L.A., 

 has informed me that during the recent very dry weather 

 (August and September) thousands of dead fish were to be 

 seen in the Wide Bay district, in Wide Bay Creek and the 

 Mary River, whose waters had become stagnant and 

 contained abundant vegetation. Amongst the affected 

 fish seen by him were jew fish {Tandanus and Neosilurus 

 hyrtlii) ; Murray cod {Oligorus macquarice) ; ceratodus (C. 

 forsteri) ; mullet {Mugil dobula) ; bony bream {Dorosoma 

 come) ; and perch (probably Plectroplites ambiguus, though 

 perhaps it may be Scicena australis)*. The epidemic 

 disappeared after the rains set in. 



*A11 names kindly supplied by Mr. J. D. Ogilby, of the Queensland 

 Museum. 



