. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 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. Aft
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 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 catch
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