FISHERY BULLETIN; VOL. 76, NO. 1 



TabLK 15. — Marked catches and escapements, catch to escapement ratios, and total survivals for fish from 

 each special mark hatchery and all study facilities combined, 1961-64 broods. 



'Assuming no mortality due to marking 

 ^Includes common marks only. 



despite the limitations, we have included the val- 

 ues in this report. 



Catch to escapement ratios for special mark 

 hatcheries (Table 15) ranged from 2.4 to 1 (Big 

 Creek, 1963 brood) to 43 to 1 (Grays River, 1962 

 brood). Average catch to escapements for Spring 

 Creek and Kalama River hatcheries were 9.3 to 1 

 and 12.0 to 1 respectively. The catch to escape- 

 ment ratios for all hatcheries combined, common 

 marks only, show much less yearly variation than 

 those for the special mark hatcheries. The average 

 catch to escapement, all hatcheries and broods 

 combined, was 8.6 to 1. Only common marks were 

 combined for all hatcheries because these marks 

 show only the variations among broods, not those 

 among marks. 



Total survivals ranged from 0.1% (Elokomin, 

 1961 brood; Cascade, 1962 brood; Little White 

 Salmon, 1964 brood) to 2.6% (Spring Creek, 1964 

 brood). Average survivals for Spring Creek and 

 Kalama River hatcheries were 1.3 and 1.0% re- 

 spectively. For all hatcheries combined, the aver- 

 age survival was 0.7% . 



Examination of Table 15 does not reveal any 

 relationship between catch to escapement ratios 

 and survivals. For example, at Spring Creek the 

 1964 brood had the highest catch to escapement 

 ratio and percent survival. At Kalama River 

 hatcheries, the 1 964 brood had the highest catch to 

 escapement ratio and the second highest survival 

 value. The 1961 brood had the lowest catch to 

 escapement and highest survival. For all study 

 facilities, the 1964 brood had the highest catch to 



200 



escapement ratio, and the 1963 brood had the 

 highest total survival. The 1964 and 1961 broods 

 had nearly equal survivals, but markedly differ- 

 ent catch to escapements. The major reason for 

 high 1964 brood catch to escapement ratios is the 

 absence of adjacent stream surveys during three of 

 the four return years for this brood. 



ECONOMIC EVALUATION 



A major purpose of this paper is to develop bene- 

 fit to cost ratios for each of the special mark hatch- 

 eries and for each brood of the combined study 

 facilities. To develop these ratios, the cost of rear- 

 ing the four broods of chinook salmon and their 

 potential value to the fisheries had to be esti- 

 mated. The development of benefit to cost ratios is 

 explained in detail by Worlund et al. ( 1969) and 

 Wahle et al. ( 1974), but certain modifications will 

 be discussed here briefly. 



The values and benefit to cost ratios are higher 

 in this report than those reported in our previous 

 reports for five reasons: 1 ) the interest rate applied 

 to capital costs is lower in this report (Wahle et al. 

 1974), 2) the sport value used is higher (see Value 

 of Hatchery Contribution), 3) a lower marked fish 

 relative survival figure was used for the 1961- 

 brood (see Contribution of Hatchery Fish), 4) mis- 

 identified and partial marks were included in this 

 report (see Contribution of Hatchery Fish), and 5) 

 the potential catch contribution figures were used 

 in this report rather than estimated catches (see 

 Contribution of Hatchery Fish). 



