United States Depar'bnent of the Interior 

 Oscar L. Chapman, Secretary 

 Fish and vaidlife Service 

 Albert M. Day, Director 



Special Scientific Report - Fisheries 

 No. 12 



BIOLOGICAL INVESTIGATIONS OF THE FISHERY RESOURCES 



OF TRINITY RIVl-IR, CALIFORNIA 



By 



James li. Moffett and Stanford H. Smith 

 Fishery Research Biologists 



CONIENTS 



Preface Page 



Introduction* ••••••••••*••...••..,••., j^ 



Physical characteristics of Trinity River •••• 5 



Run-off and flow 5 



River temperature* ••«••••••••••••••••• 9 



Existing biological conditions* •••••••••• \o 



Non»game fishes. •••«•••••••••••.••••• \q 



Residjsnt game fishes ••••••••••••••••••. 19 



Anadromous fishes* ••••••••*•••••••**•• 20 



King salmon a******************** go 



Commercial and sports fisheries* •••*•••• 20 



Characteristics of the seasonal runs ****** 21 



Spawning and development **••••.•••.* 35 



Seaward migration. ...•••• . 27 



Sex ratios of adults 34 



Silver salmon .............. ...... 40 



Steelhead trout • 40 



Pacific lamprey .• 45 



Salmon spawning bed surveys .. ...... 49 



Nest measurements. .. ........... 49 



Methods qi 



Results of surveys • .............. 51 



Effects of water development plans on the Trinity 



River fishery and suggested means for fish protection. • . • 56 



General principles of operation. ••• •••• 57 



Maintenance plans for Lewis ton Deua ••••....••.• 57 

 Development of additional spawning 



grounds in the main stream. .••.•••••••.. 57 



Improvement of tributary streams. •*•• gg 



Artificial propagation ** 69 



Maintenance plans for Browns Creek dam •• 69 



Steelhead maintenance. .•••.•••••••...•.. 70 



