demand for no re fish or the need for more knowledge of lake metabolismo 

 Considering the low degree of success in past lake-enrichment attempts, 

 the demand for greater fish crops through lake fertilization is seemingly- 

 inadequate to justify the process in this country at present. If artifi- 

 cial enrichment is to be applied to the study of lake metabolism^ experi- 

 mental d esigns must be more rigid than those used in past investigations 

 in order to procure results of greater significanceo Hasler and Einsele 

 (I9U8) stressed the importance of scientific approach to lake fertilization, 

 A thorough limnolo^-ical investigation should precede enrichment o A few 

 lakes should be tested over a number of years, or several proximate lakes 

 in a shorter time. Inherent variations in chemical and biological con- 

 stituents among the lakes 5 and normal fluctuations of these factors within 

 each lake must be considered. The experiment should then test a minimum 

 number of factors in such a manner that the results will be clear and will 

 lend themselves to statistical interpretation. 



SUMMARY 



1, Artificial enrichment and the environmental factors associated 

 with it are treated in order to describe the fertilization pro- 

 cesses and relate them to various fields of fresh-water fisheries, 

 The literature reviewed is largely North American, but pertinent 

 Asiatic and European reports are included, 



2, The fertilization mechanism involves many physical, biological, 

 and chemical factors which are complex and interrelated in the 

 aquatic habitat. Recognition of such factors is essential to 

 sound planning and interpretation of enrichment experiments. 



3, Heat, light, and dimension are the most important physical con- 

 siderations. The first two function mainly in photosynthetic 

 activity, upon which rests the fate of higher fauna. Heat and 

 light exposure of the water are limited by geographical varia- 

 tion in growing season^ occludent vegetation, and turbidity. 

 Small size and shallowness of the environment signify greater 

 relative productivity, 



ii. Biological components of a lake or pond may be classified as 

 either producers (flora and microfauna) or consumers (macro- 

 fauna) and form various food chains from nutrient matter to 

 removable fish crop. A fertilization program should consider 

 such successions and operate through the most direct route to 

 fish production. Organisms that do not contribute to the suc- 

 cess of enrichment should be suppressed. Bacteria are of 

 singular importance in bridging the gap between nutrient matter 

 and other organisms. Fluctuations in abundance, a characteris- 

 tic of plant and animal populations, may result from or occur 



27 



