2 



Artificial Aquatic Habitats 



Artificial lakes are of two kinds: (1) water impoundments for some 

 definite purpose, such as flood control, water supply, or recreation, and 

 (2) water-filled depressions with surface materials or mineral deposits 

 removed. It is interesting to note that these bodies of water show a 

 considerable diversity of aquatic habitat. Thus, artificial lakes (such as 

 lateral-levee lakes along large rivers, navigation pools created by low 

 dams across river channels, or deep main-stream storage reservoirs) are 

 biologically quite similar to natural lakes, whereas, impoundments across 

 small-drainage channels may contain limited biota, species-wise. In fact, 

 when these latter lakes are in densely populated regions, the aquatic 

 animals (primarily birds and mammals) that customarily inliabit remote 

 regions and shun close association witli man, are almost entirely absent. 

 The heavy use of a lake by recreation seekers may even drive away 

 animals only moderately man-shy. Neither coots, nor migrating ducks 

 (where protected) are wary of man, but tliey will leave a lake if boat 

 traffic becomes heavy. 



When some of the animals that ideally constitute the natural complex 

 of remote standing waters are absent from artificial lakes, interrela- 

 tionships of the living organisms that are present will differ from those 

 found in a more primitive environment. Thus when man is disparaging 

 of the kinds and sizes of fish that an artificial lake produces in contrast 

 to a natural one in some remote region, he is not making a proper com- 

 parison. The differences in animal populations inhabiting natural and 

 artificial lakes will be considered further in Chapter 5. 



Beyond the area of direct human interference is the natural migration 

 of plants and animals. Since most artificial lakes have not been in existence 

 as long as natural ones, certain organisms have not as yet had the time 

 or the opportunity to populate these newly-created waters. 



Some organisms get about much more readily dian others, many of the 

 smaller forms being carried by the wind as spores, seeds, eggs, or resting 

 stages that are protected from desiccation by waterproof coverings. 



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