FISHERY BULLETIN: VOL. 76. NO. 1 



(Table 1). This mark consisted of clipping the 

 adipose fin (Ad) and a right or left maxillary (RM 

 or LM). The maxillary clip was alternated from 

 one brood year to the next. In addition, a portion 

 (as discussed later) of the production at 11 of the 

 study hatcheries was marked with special marks. 

 A portion of four broods at Spring Creek National 

 Fish Hatchery and Kalama River hatcheries (in 

 this study, Kalama Falls and Lower Kalama 

 Hatcheries were treated as one facility) were 

 marked with the following special mark: adipose, 

 a ventral, and a maxillary clip. Spring Creek was 

 assigned the adipose, left ventral (LV), and left or 

 right maxillary clip. The maxillary clip was alter- 

 nated among brood years. The 1961 brood was 

 marked Ad-LV-RM, the 1962 brood was marked 

 Ad-LV-LM, and so on. Kalama River hatcheries 

 were assigned the adipose, right ventral (RV), and 

 left or right maxillary clip. Again, the maxillary 

 clip was alternated among brood years. Combina- 

 tions of a single ventral and maxillary were alter- 

 nated among eight other hatcheries: Elokomin, 

 OxBow, Grays River, Cascade, Klickitat, Big 

 Creek, Bonneville, and Little White Salmon. Two 

 different hatcheries were marked with this com- 

 bination for each brood year. 



Sources of Variation and Error 



Two major sources of variation in contributions 

 to fisheries are differences among brood years and 

 differences among hatcheries. To evaluate the dif- 

 ferences among broods, four broods were marked. 

 The variations among hatcheries were evaluated 

 by special marking at four hatcheries for each 

 brood year. 



One possible source of error in estimating con- 

 tributions is the combination of differential rela- 

 tive survival and differential maturation time for 

 marked and unmarked fish. If the difference in 

 marked and unmarked ratios at release and re- 

 turn were due primarily to delayed maturation 

 caused by marking, then marked fish may have 

 been subjected to more intense fishing pressure 

 due to a longer time in the ocean. This could mean 

 the ratio of marked to unmarked fish in the 

 fisheries would be greater than the ratio at release 

 from the hatcheries. If this were true, the potential 

 contributions would be overestimated in this re- 

 port. However, since we are making the best esti- 

 mate of contribution and benefit for the hatch- 

 eries, we are assuming all differences in marked to 

 unmarked ratios at release and return are due to 



182 



Table l. — fieleases of marked fall chinook salmon from Colum- 

 bia River study hatcheries, 1961-64 broods. 



'Ad: Adipose; LV: Left ventral: RV: Right ventral; LM: Lett maxillary; RM: 

 Right maxillary. 



differential survival between marked and un- 

 marked fish. This point is discussed in detail under 

 assumption 4. 



Straying of wild fish into the hatcheries, thus 

 diluting the marked to unmarked ratios at return, 

 is another source of variation and/or error. This 

 dilution would reduce the relative survival rates 

 for marked fish. To minimize this effect of varia- 

 tion and/or error, average relative survival figures 

 for common and special marked fish were calcu- 

 lated and used in the contribution computations. 



Estimating Procedures 



A formal account of the estimating procedures is 

 presented in the report by Worlund et al. (1969). 

 Simple numerical examples will be used to explain 

 the procedure in this report. Estimating the poten- 

 tial contributions and values of hatchery fall 

 chinook salmon required four steps. First, the 

 number of marked and unmarked hatchery re- 

 leases had to be estimated. Second, the estimated 

 catch of marked fish was calculated. Third, the 

 total contribution of hatchery fish was estimated. 

 Fourth, dollar values were applied to the contribu- 

 tion estimates. 



Hatchery Releases 



The numbers of marked and unmarked fish in 

 hatchery releases were estimated by sampling the 

 hatchery population with a 10-part sampler (see 

 Marking and Release Procedures). This device 



