W. RUSHTON 79 



to three or four times above the normal. The temperature may fall a 

 degree or two but not to any marked extent. 



After the acidity has risen it remains high for some hours and then 

 very gradually comes down, taking often several days to get anywhere 

 near the normal figure. 



It is known by long experience that sudden changes in the weather 

 are very trying for fish under artificial conditions and many young fish 

 are lost on this account, older fish being able to withstand the changes 

 much better than the young ones. 



It has been found that the bloom makes its appearance immediately 

 after this sudden rise in acidity, and from all experiments tried on the 

 spot (and repeating as near as possible in glass tanks the condition of 

 sudden rise in acidity, keeping the fish under observation all the time) 

 it is found possible to produce artificially a somewhat similar appearance 

 to what occurs at this hatchery, not forgetting that the water at the 

 hatchery also contains a certain amount of vegetable matter in sus- 

 pension and a certain number of vegetable toxins. 



Dachnowsky in the Botanical Gazette, 1909, gives an account of vege- 

 table toxins which are detrimental to animal and plant hfe and w^hich 

 occur in peat water at different times of the year. 



Examination of a large number of fish which have died through 

 bloom always show^s the mouth and gill covers extended to their widest 

 extent with the tips of the gill filaments covered with a thick layer of 

 coagulated mucous, the stomach is invariably swollen, containing no 

 food but varying amounts of coagulated mucous. 



The first quarter of an inch of the intestine immediately following 

 the pyloric end of the stomach is usually inflammed, due, I take it, to 

 the high acidity of the contents of the stomach set up by the acid mucous. 



Many experiments have been tried to effect a cure both on the spot 

 and in the laboratory. Various reagents have been tried, but the most 

 effective appears to be powdered hme, chalk, or lime water. 



It has been found that causing the water to run through chalk filters, 

 which hardens the water a httle and brings down the acidity, is effectual; 

 as is also the careful addition of hme to the w^ater at a point w'here no 

 free hme would be able to reach the hatchery. But the easiest and the 

 most economical w^ay has been by using hme water. 



Calculating the average rate of flow and the highest acidity known 

 to occur, it has been found possible by turning some of the ponds into 

 hme-pits, and arranging that a certain amount of hme water flows in 

 gradually to so regulate matters that this bloom no longer appears. 



