More cold-water lakes have been fertilized than the above-mentioned 

 warm-water lakes » Perhaps this is because they are "poorer producers", 

 lower in mineral solutes, and therefore considered better enrichment poten^ 

 tialso A superficial fertilization of the centrally located lake m a 

 chain of three, with l5 tons of sea mussels, was reported by Smith (1931). 

 Marked plankton increases in the fertilized lake, and in the lake below it, 

 were noted the following year„ Taylor (I9UI1) discussed the fertilization 

 of a clear-.vater, sand-bottom trout lake with 1^:8:10 plus calcium carbonate, 

 indicating a large increase in trout weight attributed to fertilization. 

 The content of these reports does not justify more than passing comment. 



One phase of a trout investigation project, reported by Wales (19$0), 

 involved the organic enrichment of a clear, deep (120 feet^ maximum), alpine 

 cligotrophic lake supporting four species of salmonids and some forage fish„ 

 Pretreatment water analysis showed 3U parts per million total dissolved 

 solids, a hardness of 23 parts per million, and a pH near neutralityo Cot- 

 tonseed meal was selected on the basis of promising results shown by Juday 

 et al„ (1938). The only apparent change was an increase in turbidii.y im- 

 mediately following fertilization. Langford (19^0) fertilized four deep 

 lakes, thermally stratified, with inorganic 12;2li:12 at monthly intervals. 

 This preliminary report considered detailed changes in plankton abundance. 

 A definite increase in phytoplankton occurred within 3 weeks to 1 month 

 after nutrient application, and it appeared that only a single spring 

 addition was utilized by these organisms. In conjunction with the fertil- 

 ization of a warm-water lake (discussed above). Ball (1950) reported the 

 artificial enrichment of one of a pair of sand-bottom trout lakes. As in 

 the warm-water lake, excessive summer growth of algae fostered winter 

 anaerobiosis which caused the d eath of fish and insects in the f ertdlized 

 lake. 



The fertilization study of a shallow, soft-water lake containing brook 

 trout and four species of rough fish was made by Smith (19U8a^ 19USb) , A 

 single application of ammonium phosphate and potassium chloride in late 

 spring caused a zooplankton bloom which disappeared later in the season dur- 

 ing a bloom of Anabaena, Postf ertilization observations within the same 

 year showed an increase in bottom fauna, oxygen saturation, and carbon-= 

 dioxide reserve over pref ertilization levels. Water phosphorus remained 

 somewhat above normal during the season. Indications of increased trout 

 gi'owth and angling success were obtained the following season (I9h7' when 

 the yield of trout to anglers (3=6 pounds per acre) more than doublea the 

 average returns for a 2=year period before nutrient addition. This was 

 attributed to catches of rapidly growing stock fish (60 percent of total 

 catch) which previously grew slowly and constituted only a sm,all part of 

 the creel returns. Observations in t he succeeding years (Smith, 1952) 

 showed a decline in fishing returns. The author concluded that further 

 benefits to trout were masked by predators which also profited from the nu- 

 trient enrichment, and that predator control plus a supply of trout to cap- 

 italize on the increased food supply are requisites for successful 

 fertilization. 



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