WINTER-RUN CHINOOK SALMON IN 

 THE SACRAMENTO RIVER, CALIFORNIA, WITH 

 NOTES ON WATER TEMPERATURE 

 REQUIREMENTS AT SPAWNING 



by Daniel W. Slater 



Bureau of Sport Fisheries and Wildlife 



Fish and Wildlife Service 



U.S. Department of the Interior 



ABSTRACT 



Salmon specialists throughout the Pacific Coast indicate that the winter-run 

 Chinook salmon is restricted to California's Sacramento River system. The char- 

 acteristics and habits of the race are unique in the following respects: Fresh-water 

 holding period, December to April; spawning period, April into July. The up- 

 migration is concurrent with the late segments of the fall run, but the adults are dis- 

 tinguishable by the green condition of the gonads. The down-migration is concurrent 

 with that of the spring-run fry, but the migrants are 2-inch or larger fingerlings. 

 Evidence is lacking to determine whether there is an earlier down-migration of fry. 

 The race appears to hold great promise as a stock to be introduced into areas 

 where May-August temperatures are 42. 5° - 57.50 p_^ for it supports superb 

 angling during the fresh-water holding period. Water temperatures in May through 

 August are seen as the factor limiting the natural extension of the range of the race. 



Fry (1961) states that winter-run fish are 

 the least known and probably the least abundant 

 of the Central Valley Chinook (king) salmon 

 runs. This paper is intended to shed a little 

 light on the first point and discount the latter 

 point. 



Winter-run Chinook salmon (Oncorhynchus 

 tshawytscha) have been known to Upper Sacra- 

 mento Valley residents and to students of Cali- 

 fornia salmon for many years. They have been 

 mentioned, usually in an offhand way, in the 

 literature many times. Yet, one gathers from 

 discussion and correspondence with salmon 

 workers that these fish are little understood. 



Basically, four reasons are indicated for 

 this lack of understanding: (1) Concurrence 

 of both the adult run and the fisheries dependent 



upon it with the latest segments of the fall run, 

 (2) occurrence of the adult fresh-water stages 

 during winter and spring when observation is 

 difficult and seldom practiced, (3) isolation of 

 winter-run spawners during the years prior 

 to construction of Shasta Dam in inacces- 

 sible sections of the McCloud River, and (4) 

 until recently, the numerically small size of 

 the runs. Historically, no distinction of winter- 

 run fish was made in either the sport or the 

 commercial river fisheries. The "green" con- 

 dition of the gonads would have distinguished 

 them in the inland waters from the late fall 

 run, but apparently few, if any, were taken 

 there until 1949 following their displacement 

 to holding and spawning areas of the mainstem 

 Sacramento River downstream from Shasta 

 Dam. Had their habits been understood, it 

 seems likely that efforts would have been made 



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