Importance of Studying Total Populations 7 



of fish and the stocking of artificially propagated and reared fish.^^] 

 Methods of lake improvement would need to be enormously perfected, 

 before this new practice, if ever, could be expected to replace the older 

 means of maintaining the fish supply." (Bracketed matter mine.) 



Hence, the book, "The Improvement of Lakes for Fishing" has its 

 greatest importance in that it initiates a rather bold break with the past, 

 points toward tilings to come, and presents a precise picture of current 

 thinking in 1938; whereas, the actual lake-management data which it 

 contains is of less significance. 



IMPORTANCE OF STUDYING TOTAL POPULATIONS 



An important step in the understanding of fish-management problems 

 was the censusing of populations of fish by the poisoning or draining of 

 lakes so that a population could be observed as a unit.^' ^^ Such a census 

 was particularly enlightening when conducted on a lake population with 

 past stocking and fishing records available, because, under such cir- 

 cumstances, the effects of stocking could be evaluated and good or poor 

 fishing associated with a specific population. Almost immediately it 

 became evident that there was never a shortage of fish; in fact, usually 

 there appeared to be an overabundance of individuals, particularly of the 

 fish of smaller sizes. 



When many complete fish censuses became available, some of the 

 causes for poor fishing were obvious: (1) an excess of undesirable fish, 

 that is, the domination of these populations by species of no interest to 

 anglers, whereas, proportionally, the number of acceptable fish was so 

 small that the chance of catching them was remote; (2) an excess of 

 desirable fish, that is, in populations containing only hook-and-line species, 

 overpopulation led to stunting, so that few of them were large enough to 

 interest fishermen. Thus, the causes for poor fishing were domination by 

 undesirable fish and the overpopulation of desirable ones with consequent 

 stunting. This type of information gave direction to attempts at fish 

 management, something that had been lacking before. 



At this time, several studies of entire populations helped to give us an 

 understanding of certain aspects of population dynamics. Thompson,^^ 

 who took periodic samples of the fish population of Lake Senachwine 

 (Illinois) with wing nets and used the mark-and-recovery method of 

 population estimation, came to the conclusion that the "fine" fish com- 

 ponent of this population ( consisting of largemouth bass, crappies, blue- 

 gills, and other centrarchids ) totaled between 50 and 55 pounds per acre, 

 regardless of whether the lake level was high and the area was 6000 acres 

 in extent or whether it was reduced by drought to 3000 acres or less. 

 Moreover, the poundage was constant from year to year, in spite of a 



