-51- 



proportions of the population,, However, both the black and white crappies, the 

 largemouth bass, and the rock bass were known to be more abundant at Upper 

 Spavinaw than indicated by the rotenone returns o Both crappies and the rock 

 bass were commonly taken by wire traps in waters deeper than afforded by the 

 rotenoned area, and a majority of the adult bass population appeared to be re- 

 stricted to the open waters where they were often observed, as previously 

 mentionedo 



A most significant shortage noted in the Heyburn rotenone collections 

 was that of the forage species, particularly the gizzard shad. The shad is 

 the principal food of bass^ crappies, and most other carnivorous forms in 

 practically all large reservoirs where shad occur o They normally are present 

 in enormous abundance, usually exceeding all other species in weight, as well 

 as numbers. In the previously mentioned rotenone collections made at Grand 

 Lake, Lower Spavinaw, and Claremore City Lake, shad made up about 66, 78 and 

 52 percent, respectively, of the total weight of all fishes and represented 

 73 o 7 percent of the total weight in the Upper Spavinaw sample » 



In the Heyburn sample shad represented 4=3 percent of the total weight of 

 all fish recovered in 1954 and 10 ,.6 percent in 1955. Minnows and the common , 

 sunfishes also were scarce „ All sunfishes represented less than 3 percent of 

 the total weight of fishes. 



The low population figures indicate that some strong limiting factor was 

 in operation= The plankton feeders were certainly limited by the low level of 

 plankton production, as will be discussed later. Carnivorous forms were just 

 as certainly limited by the scarcity of these forage species upon which they 

 are dependent for food„ It also seems evident that reproduction of all species, 

 with the exception of the catfishes, was limited to some degree by the high 



