FORTY-FOURTH BIENNIAL REPORT 



41 



reservoir has not affected its spawning, and it is utilizing 

 the open waters not previously used by the other fish. 



Two introductions of this fish were made into Lake 

 Havasu on the Colorado River, one in December, 1954, 

 and another in March, 1955. By July, 1955, shad were 

 found throughout the river from below Davis Dam 

 to Yuma, Arizona, and in the Salton Sea. In April, 

 1956, an extensive evaluation program was begun. The 

 results to date show that the shad is being utilized by 

 the largemouth bass as forage. There is some indica- 

 tion of an increased growth rate for the bass that 

 started in the spring of 1955 when the shad were 

 populating the river at a rapid rate. The relationship 

 of the shad to the channel catfish is not clear. The 

 evaluation program is only in its initial phase, however. 



Increased angler success at Lake Havasu has been 

 attributed to the shad. 



Puddingstone Reservoir, Los Angeles County, was 

 stocked with shad in March, 1955. They have done 

 very well here and appear to have favorably influenced 

 the fishery. The survival of largemouth bass has been 

 increased. 



POPULATION STUDIES 



In warmwater impoundments the fishery is sup- 

 ported by a number of different kinds of fish rather 

 than just one or two as in trout waters. This compli- 

 cates management practices as control or heavy use 

 of one fish often markedly affects the numbers or 

 success of other fish. Because of the close relationship 

 between forage fish, sport fish and rough fish, such 

 as carp, a knowledge of population size and composi- 



tion is essential for intelligent management. It may be 

 possible, for instance, to improve the fishing in a water 

 by the control or introduction of different fish. An 

 example of such a manipulation is the introduction of 

 the threadfin shad into the Colorado River. 



This population information is gathered in a number 

 of ways, some of which are by no means simple. A 

 short-term, intensive survey method has been devel- 

 oped and applied in waters throughout the State from 

 Modoc County to San Diego County. 



Included in these surveys were: Big Sage Reservoir, 

 Modoc County; Lower Susan River, Lassen County; 

 Millerton Lake in Fresno and Madera Counties; Pardee 

 Reservoir in Amador and Calaveras Counties; Turlock 

 Reservoir, Stanislaus County; several San Diego 

 County reservoirs and Salt Springs Valley Reservoir, 

 Calaveras County. Much of the information gathered 

 in these studies is now being applied in the manage- 

 ment of the waters. 



PRE-IMPOUNDMENT SURVEYS 



Two pre-impoundment surveys were made. The 

 American River above the Folsom Dam site was sam- 

 pled in 1955 and again in 1956, as was Putah Creek 

 above the Monticello Dam site. The information ob- 

 tained will be used in the management program for 

 the completed reservoirs. Evaluation of rough fish 

 removal prior to the flooding of new reservoir basins 

 is also in progress. 



In 195 3 a largemouth bass tagging study was begun 

 at Clear Lake, Lake County. The purpose of the study 

 was to determine the harvest rate for this species. 



Boat launching beach at Folsom Lake, one of the State's newest warmwater takes. 



(Fish and Game Photo) 



