FORTY-FIFTH BIENNIAL REPORT 



49 



was found to be seriouslv diseased, and it was not 

 allowed to enter California. 



Alost of the diseases and parasites at state hatcheries 

 responded readily to treatments. Controlling the gill 

 fluke Savgumicola davisi at Darrah Springs Hatchery 

 required an approach not usually employed in hatch- 

 eries. 



Because no drugs or chemicals were known to con- 

 trol this parasite, a biological method was employed. 

 After the life cycle of this worm had been studied it 

 became apparent that removal of the snails (which 

 were found to be the intermediate hosts) and the wild 

 fish (the definitive hosts) from the water supply 

 would break the life cycle. The water supply ditch 

 was cleaned \\ ith a bulldozer which mechanically re- 

 moved man\' snails as well as the aquatic plants im- 

 portant in their habitat. The water supply was treated 

 with chlorine which removed the fish. After a short 

 period it was found that a few fish had survived in the 

 water supply. 



Due to the hatchery production schedule, it was 

 not possible to retreat the water supply. However, in 

 the following vear's fish production it was found that 

 the gill fluke had been virtuall\' eliminated, and no 

 losses of fish were attributed to the parasite. 



TROUT RESEARCH 



Much of the effort of the federal aid trout research 

 project was devoted to a search for methods of im- 

 proving the state's large catchable trout planting pro- 

 gram. Approximately 500 waters are managed as 

 catchable trout fisheries, and by far the largest portion 

 of the department's inland fisheries budget goes 

 toward this program. 



The project has developed a statistical procedure 

 from which the number of trout ultimately caught 

 from any particular plant can be determined from a 

 few days of field work. These field methods and sta- 

 tistical procedures have been tested on 28 catchable 

 trout waters. In the great majority of the waters 

 studied thus far, more than 50 percent of the planted 

 trout are caught. 



Some waters have shown a return in excess of 90 

 percent of a plant. These are represented by June 

 Lake and Rush Creek of Mono Count\-, Green V^alley 

 Lake and the South Fork Santa Ana River of San 

 Bernardino County, and Little Truckee River of 

 Sierra County. In general, such high returns are a 

 reflection of high angling pressure, as shown below. 



California catchable trout waters support angling 

 pressure which far exceeds that found in wild trout 

 waters. The project has found that the angling hours 

 per acre per day of catchable trout waters exceed the 

 angling hours per acre per year of most wild trout 

 fisheries. 



The department is further analyzing angler use on 

 catchable trout waters by comparing the number of 



fish planted in a given \\ater with the total angler 

 hours of fishing on that water. 



Upon completion of the statewide studies the de- 

 partment will be in a better position to improve and 

 further standardize the catchable trout program 

 throughout the state. Quality of catchable trout man- 

 agement depends upon the accuracy and application 

 of information on number of trout planted per angler 

 hour and the percentage return of those trout. 



MANAGEMENT EXPERIMENTS 



The experimental trout management work in the 

 Lakes Basin Recreation Area of Sierra County con- 

 tinued. In this area different species and strains of trout 



Planting Trout 



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