FRESHWATER FISH EPIDEMICS IN QUEENSLAND RIVERS. 191 



(i) Thomson River. — Longreach recoids for 1917 shew that 

 June and July of that year were both colder and drier than in 

 the average year (2-7° and 67 points less for June; 11° and 

 77 points less for July). An outbreak occurred in July. The 

 lowest minima recorded during June and July were 32-2° on 

 22nd June and 35-5 on 5th July. Thus, although both months 

 were colder and drier than usual, the thermometer reached 

 freezing jDoint only once. We are not aware of the condition 

 of the river prior to the outbreak. 



The outbreak which occurred in March 1918 can scarcely 

 have had any dependence on the temj)erature. The record3 

 again shew that it was colder (by 4-7°) and drier (140 points less) 

 than the average, but the lowest minimum recorded \\'as only 

 51°, viz., on 18th March. 



The rainy season had begun early in November 1917. 

 The Thomson was in high flood during part of January and 

 February 1918, and was still running when the outbreak began 

 in March {vide Mr. Mill's letter of 30th March), there being no 

 stagnant water at the time. 



June 1918 was again colder and drier (2-3° and 85 points 

 less) than the average, wliile the lowest minimum (35-2°) 

 occurred on the 28th. In July, hoAvever, a more decided cold 

 snajD was experienced ; for the nine days following 8th July 

 the minimum records were consistently low, culminating in 

 three nights of frost — 28-5° on the loth, 27° (lowest recorded) 

 on the 16th, and 31-7° on the 17th. After this no further 

 frosts Avere experienced. 



No rain fell in the district during May, June, or July, so 

 that the river was fairl}^ low when the outbreak began at the end 

 of July. The epidemic Avas at its height during the first AA'eek in 

 August and had abated completely by the middle of the tliird 

 Aveek. ShoAAcrs of rain yielding 45 points fell on 3rcl and 4th 

 of August. During September 1918 no rain fell. The minimum 

 temperature fell to 36° on the 5th, this being the loAvest for the 

 month, though the three succeeding days experienced 'oav 

 minima. 



An outbreak occurred during the latter half of December 

 1918, extending into early Januar}^ 1919 (midsummer), Avhen 

 the temperatures Avere certainly not Ioav. It Avas a A-ery dry 

 period and ;he Avater Avas stagnant. Another made its appear- 

 ance in July and early August 1919, but particulars as to the 

 AA'eather are not in our possession. 



