80 LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



sulphate per million." In soft water, fish and aquatic invertebrates are 

 much more susceptible to copper poisoning. The addition of 3 ppm to a 

 soft-water Nova Scotia lake by Smith (1935) resulted in nearly a complete 

 kill of fish and fish food. 



It should be noted that fish kills may result from the use of copper 

 sulphate and not be due to copper poisoning. If treatment is delayed until 

 a heavy algal crop is present, decay of the algae killed may so reduce the 

 supply of dissolved oxygen that fish die of asphyxiation. 



Algal Control and Fish Yields 



In the simplest sense algae are the grass of our waters. They, with 

 the larger aquatic plants, are the synthesizers of organic material on which 

 all other aquatic life depends. This general statement is an over-simplifi- 

 cation, since the interrelationships within the aquatic "microcosm" are 

 immensely complex, but it does pose a very pertinent question. Will the 

 reduction of algal crops through the use of copper sulphate seriously affect 

 the potentialities of a water for raising fish and waterfowl? 



Approaches to this problem in the literature are few and of an obser- 

 vational nature. Huff (1923), after considering 6 years of algal control 

 with copper sulphate in Lake Vadnais, near St. Paul, observes that "Fish, 

 . . . are apparently as abundant as they ever have been." Domogalla (1935) 

 in reviewing 11 years treatment of Lake Monona, at Madison, does not 

 commit himself to a definite answer but remarks "the opinions of fisher- 

 men on that subject (effect of copper sulphate on fishing) vary a good 

 deal." This problem has recently been brought to the attention of sports- 

 men by Schoenfeld (1947) in an article in Field and Stream, in which he 

 makes a general condemnation of the use of copper sulphate for algal con- 

 trol. He cites an unnamed Illinois pond which has been treated with 

 copper sulphate for 30 years and is "now completely sterile." He states that 

 perch fishing in Lake Monona, which has been treated, is poor compared 

 to untreated Lake Mendota. There is also negative evidence which per- 

 haps should be considered. With the exception of Schoenfeld's article, 

 no account has been found in which a decline in fishing has been proven 

 to be the result of continued use of copper sulphate for algal control. 



The longest history of copper sulphate treatment in Minnesota is that 

 of the Fairmont water supply. Here since 1921 algal growths have been 

 controlled in Amber, Budd, Hall, and Sisseton Lakes. These lakes are 

 part of a chain lying in an ancient glacial river valley in Martin County. 

 They range in size from 84 to 513 acres, in average depth from 5.4 to 11.4 

 feet, are very hard and of high chemical fertility. Aphanizomenon is, and 

 has been since 1921, the principal objectionable algae (Huff 1922; Moyle 

 and Wilson 1946). Microcystis is also present and has at times been 

 troublesome. Poisoning of livestock drinking from Hall Lake has been 

 attributed to it (Fitch et al. 1934) . 



The Fairmont water supply lakes, together with untreated waters in 

 the same chain are quite heavily fished by anglers. All have large rough 



