42 



DEPARTMENT OF FISH AND GAME 



paign by sponsoring semiannual prize drawings for 

 persons \\ho returned tags. Merchandise and cash 

 prizes were awarded to anglers selected at random. 



Considerable data concerning life history of the 

 delta catfish is being collected at regular intervals. 

 Although much laboratory work remains to be com- 

 pleted, this phase of the project is progressing well. 

 A check is being maintained on the effect of the re- 

 moval of the commercial fishery and from all indica- 

 tions the ban was a sound move. Angling seems to 

 have improved and the average size of the catfish 

 definitely has increased. 



Since the Sacramento-San Joaquin Delta supplies 

 appro.ximately 50 percent of the catfish caught in 

 California, close contact with the fishery will be main- 

 tained for the duration of the project. Information 

 provided by project investigations should enable the 

 department to insure wise utilization of this important 

 resource by regulations based on facts. 



Other important catfish areas receiving attention 

 from the project were Clear Lake and the Colorado 

 River. In 1952, 1,500 white catfish and brown bull- 

 heads wxre tagged in Clear Lake in order to determine 

 the rate of exploitation. Returns after one year in- 

 dicated a minimum annual fishing mortality of only 

 2.5 percent. 



Because of doubts as to the validity of these results, 

 another tagging experiment is planned for the winter 

 of 1955. Food habits of Clear Lake catfish and bull- 



heads are under study also. This work will, among 

 other things, define the degree of competition between 

 catfish and largemouth black bass and the effect of the 

 insecticide, TDE, upon the food supply of the catfish. 

 This insecticide has been used in the control of the 

 Clear Lake gnat. 



A survey of the Colorado River channel catfish 

 population was conducted in 1954 with several hun- 

 dred fish tagged and released near Blythe. Tag returns 

 have been numerous in spite of the short interval since 

 the catfish were released. Apparently the Colorado 

 River channel catfish population is under heavy fish- 

 ing pressure and results of this study will guide the 

 Department of Fish and Game in recommending 

 sensible bag limits. 



A survey of catfish populations in Northern Cali- 

 fornia will be made during the summer of 1954 in 

 response to requests by sportsmen for more liberal 

 catfish bag limits in that area. 



Fish Disease Studies 



In the spring of 1953 the fish parasitologist's head- 

 quarters were shifted to the Berkeley Fish and Game 

 Disease Laboratory of the Game Management Branch. 

 Investigations on diseases of hatchery and wild fish 

 continued. "Trouble shooting" at the hatcheries was 

 actively pursued, and a large number of visits were 

 made to assist the regions with the prevention and 

 control of disease. 



