FORTY-SECOND BIENNIAL REPORT 29 



Echo Lake, El Dorado County. Studies to determine the reasons for the poor angling 

 success in this lake continued during the biennium, with emphasis placed on ascer- 

 taining the extent of game fish exodus from the lake through the outlet stream 

 and the diversion canal. This was accomplished through the annual planting of 

 25,000 trout marked for future identification and trapping of downstream migrants. 

 The fish trap on the outlet stream was operated continuously except for short 

 periods during flood stages, and fyke netting operations were conducted on the 

 diversion canal during the diversion period of 1951. These studies showed that 

 there is a negligible loss of game fish from the lake through the outlet stream and 

 diversion canal. 



Donner Lake, Nevada County. Observations were conducted on the spawning runs 

 of kokanee red salmon (Oncorhynchus nerka kennerlyi) in 1950 and 1951 and 

 studies made of scales and other data in connection with the management of the 

 fishery. 



Lake Tahoe, El Dorado-Placer Counties. Studies were concentrated on the intro- 

 duction of kokanee salmon to this lake. Potential lake shore and tributary stream 

 spawning areas were located and plotted. Allotments of salmon were carefully 

 planned for the various available spawning areas to take advantage of any possible 

 homing instinct on the part of the salmon. Field checks failed to confirm authentic 

 catches of kokanee during the biennium. 



Halt Springs Valley Reservoir, Calaveras County. In the fall of 1951, a population 

 study of the fish in this lake was made, using the Schnabel mark and recapture 

 method. Results will be published in California Fish and Game. 



Lake Merced, San Francisco County. Evaluation of the results of catchable trout 

 stocking in this lake was carried on throughout the biennium. 



Clear Lake, Lake County. Standard test seine hauls for checking fish of the year 

 were made annually at five stations. No significant increase or decrease was noted 

 in any of the important game species, although forage species continued to be 

 scarce. A continuing check on forage minnow spawning was maintained on the 

 tributaries; the 1952 spawning run of hitch (Lavinia exilicauda) was the largest 

 noted for many years. 



Upper Blue Lake, Lake County. A study of this lake was begun in 1952 to de- 

 termine which species are best fitted for it and to learn what management tech- 

 niques might be applied to increase its productivity. A temporary barrier to rough 

 fish was installed at the outlet in 1952. 



Mad River, Humboldt County. A controlled program to study the economics of 

 planting king salmon, silver salmon (0. kisutch) , and steelhead trout (Salmo g. 

 gairdneri) artificially reared to varying ages was started. Marked fingerlings are re- 

 leased in the stream and examined as returning adults at the Sweasey Dam count- 

 ing station and in the sport catch. Approximately 10 percent of all salmon taken in 

 the California commercial catch are being examined for marks by the Bureau of 

 Marine Fisheries, so that the contribution of the Mad River salmon to the com- 

 mercial fishery will be included in the study. A biological survey of the entire 

 river system is also being made as part of the study. 



Millerton Lake, Fresno-Madera Counties. An intensive study of the Millerton 

 Lake warm-water fishery, as a typical example of the large fluctuating reservoirs 

 along the west slope of the Sierra Nevada, was started in 1949. Since 1951 em- 

 phasis has been placed on environmental and fish population studies. Intermediate 

 levels in the normal food chains are weak and it is possible that introduction of 

 forage fish, which will be carried out at an early date, may help to' fill the gaps. 

 Considerable time was devoted to preparing material from the earlier work for 

 publication. 



Rush Creek Test Stream, Mono County. Operation of the project during the trout 

 fishing season was continued through the biennium. Results confirmed earlier 

 indications of returns of 70 percent or more to the angler from in-season plants of 

 catchable rainbow trout in streams. Minor stream improvement work in the 

 nature of additional pool construction appeared to benefit the stream during 

 the 1951 summer, when the flow was extremely low. 



San Vicente Reservoir, San Diego County. A largemouth blackbass-bluegill 

 ( Micropterns salmoides-Lepomis macrochirus) tagging study was completed. 



Vail Reservoir, Riverside County. A fish population study was conducted, a man- 

 agement plan prepared, and a catch record system established. 



