residence. In June 1960, the reservoir was 

 treated with rotenone in an attempt to remove 

 both salmon and resident rainbow trout, Salnio 

 gairdiieri Richardson. Survival of the salmon, 

 to this time, was estimated to have been 90% . 



In the present study, the reservoir received 

 two plantings of spring chinook salmon fry: 

 on 8 February 1961, 75,300 unfed fry at 3,300/ 

 kg from the Bureau of Spoil Fisheries and 

 Wildlife hatchery at Carson, Wash.; and on 22 

 March 1962, 150,000 advanced fry at 2,200/kg 

 from the Bureau of Sport Fisheries and Wildlife 

 Eagle Creek hatchery at Estacada, Oreg. 



A fry planted in 1961 is called a 1961 year 

 class fish; it is designated as 0-age from Febru- 

 ary 1961 to Febnaary 1962 and as age class I 

 from February 1962 to February 1968, so that 

 the Roman numeral corresponds to the number 

 of winters spent in freshwater life (Koo, 1962). 



FISHERY BULLETIN: VOL. 71, NO. 3 



From 14 to 59 chinook salmon were collected 

 at approximately 1 mo intervals for food and 

 growth studies. These collections, in addition 

 to the more extensive ones for survival estimates, 

 were made by means of gill nets and beach 

 seines, and by angling. Each fish in a monthly 

 sample was measured for fork length to the 

 nearest millimeter and weighed on a double- 

 pan balance to the nearest 0.1 g. Fish to be used 

 in the food analyses were preserved in 10% 

 Formalin-* after their body cavities had been 

 slit open. The exception to this procedure in- 

 volved the recently planted fish, which were 

 preserved in 70% ethyl alcohol or 5% Formalin 

 prior to measurement. 



The condition factor for each fish was com- 

 puted from the following formula, as modified 

 from Rounsefell and Everhart (1953): 



K = lOOWIL-' 



METHODS AND MATERIALS 



A stadia survey and depth sounding provided 

 data from which a hydrographic map was made. 

 Area and volume were computed from this map. 

 Temperature patterns of the upper strata of 

 water were recorded with a maximum-minimum 

 thermometer and constant-recording thermo- 

 graphs. A transistorized thermometer was used 

 to take vertical temperature series. Light pene- 

 tration was measured with a Secchi disc. 



A Kemmerer water bottle was employed to 

 take water samples in vertical series for pH and 

 dissolved oxygen determinations. The Winkler 

 method was used for oxygen determinations, 

 and either a color-comparator or portable con- 

 ductivity meter was used to measure pH. 



Other determinations made were total dis- 

 solved solids, volatile dissolved solids, total 

 phosphorus, and methyl orange alkalinity. The 

 same water sample sufficed for the first two; 

 after the suspended solids were removed by 

 centrifugation, the sample was evaporated at 

 60°C and ashed at 600 °C for these measure- 

 ments. The phosphorus analyses were conducted 

 by the analytical laboratory of the Department 

 of Soils at Oregon State University. A 0.02 N 

 sulfuric acid solution was used in the titration 

 for methyl orange alkalinity. 



where K = a. condition factor near unity 

 W = weight in grams 

 L = fork length in centimeters. 



In preparation for stomach analyses, the pre- 

 served fish were transferred to 5% Formalin 

 and eventually to 20% isopropyl alcohol. Ten 

 fish from each sample were chosen for analysis. 

 Only the contents of the anterior halves of the 

 stomachs were removed in order to reduce error 

 caused by partially digested foods. The stomach 

 contents were pooled and thoroughly mixed, 

 and a random subsample was extracted for dry- 

 weight analysis. 



Population estimates were determined 

 through the mark-and-recapture method. Fish 

 were captured with seines, anesthetized in a 

 solution of quinaldine (8 to 12 ppm), marked 

 with a fin-clip, and then distributed over the 

 reservoir in accordance with the apparent dis- 

 tribution of the population. Fins clipped in- 

 cluded both pelvics and anterior third of the 

 anal fin on the 1961 year class, and adipose and 

 posterior third of the anal on the 1962 year 

 class. 



Salmon which migrated from the reservoir 

 via spillway outflows were captured in an 



( 



^ Reference to trade names does not imply endorsement 

 by the National Marine Fisheries Service, NOAA. 



878 



