Reservoir Management 11 



tion in the early years of impoundment resulted from organic decay in 

 the new lake basin was largely disproved, since this cycle of production 

 could be repeated as often as the reservoir was completely drained (or 

 poisoned) and restocked with small numbers of fish J In addition, the 

 hypothesis of progressive loss of fertility that had been advanced could be 

 attacked in some situations on the basis of the fact that the amount of 

 flooded vegetation in a lake basin was too meager, in relation to the huge 

 volume of water impounded, to produce a "hay infusion" that would result 

 in an initial high fish production. 



Recent Advances in Management 



In 1945 the Federal Office of River Basin Studies was formed. Within 

 the framework of this organization, biologists could appraise the fishery 

 resources of a river before a federal impoundment was built and thereby 

 estimate the eflFect of the impoundment on that resource. Although these 

 benefits or losses were incorporated in the cost-benefit ratios prepared by 

 the U.S. Corps of Engineers, the predicted gains or losses of a fishery 

 seldom influenced the decision to build a reservoir. 



In 1944, Norris Reservoir (Tennessee) was opened to year-round fish- 

 ing; the results were so encouraging that Tennessee dispensed with a 

 closed season on all of its remaining reservoirs in 1945, as did Ohio that 

 year and some additional states shortly thereafter. 



After World War II there was a marked expansion of studies of fish 

 populations in reservoirs, particularly in the states of Tennessee, Kentucky, 

 Missouri, Oklahoma, Texas, and California. In many instances there 

 seemed little to be done that would have any effect upon the fish popula- 

 tion of a large reservoir, and the fishermen and biologists were forced to 

 go along with fish population changes resulting from natural biological 

 phenomena.^^ 



Phases of Operation. By the late 1950's, reservoir management had been 

 reduced to about five phases of operation: (1) The manipulation of water 

 levels to favor ceHain species and depress others.^' '^'^'^^'-^'^^'^^ (2) The 

 addition to reservoirs of certain species not originally present, in order to 

 contribute directly to the creel or to "fill in" indirectly the trophic levels 

 in the food chain of some important fish already present. Good examples 

 of the first type of addition are to be found in the introduction of the 

 white bass and striped bass (the striped bass was isolated in the Santee- 

 Cooper Reservoir and then added to Kentucky Lake ) . On the other hand, 

 the introduction of the threadfin shad is an example of a "fill in" fish to 

 improve food conditions for game fish.--^ (3) The control of overabundant 

 rough fish and/ or forage fish to reduce their competition with game fish 

 for food and space. There was a need for more efficient methods of con- 

 trolling these undesirable fish, of which the rough fish species were 



