WAHLE and VREELAND: BIOECONOMIC CONTRIBUTION OF FALL CHINOOK SALMON 



cause marked fish are smaller than unmarked fish 

 (Cleaver 1969). Weights for the ocean troll fish- 

 eries are dressed weights and those for Columbia 

 River net fisheries are round weights. Ex-vessel 

 market prices have been used to represent esti- 

 mated net values for commercially caught fish. 

 The ex-vessel prices were obtained from 

 Washington Department of Fisheries records for 

 the appropriate years and age of fish. (D. Ward, 

 Washington Department of Fisheries, pers. com- 

 mun.) Washington troll prices were used for other 

 commercial fisheries on the Pacific Coast. 



The net value for salmon and steelhead sport 

 fishing is estimated to be $20/day of fishing. This 

 value results from reconciling the existing re- 

 search that is closely related to estimated net 

 economic values of Columbia River sport caught 

 salmon. The maximum potential benefits from 

 sport fishing at a single market price is predicted 

 at $20/fishing day (Brown et al.^"). The salmon 

 catch per angler trip data were obtained from 

 Washington, Oregon, and California publications 

 (Campbell and Locke 1964, 1965, 1966, 1967, 

 1968, 1969; Nye and Ward undated a, b; Green- 

 hood and Mackett 1967; Haw et al. 1967; Heimann 

 and Frey 1968a, b; Heimann and Carlisle 1970; 

 Pinkas 1970). An estimate of 1.09 salmon/angler 

 trip was obtained by averaging data for the three 

 States over the appropriate years. The $20/angler 

 trip was divided by 1.09 salmon/angler trip to 

 yield a value of $18.35/salmon. This value was 

 used in the ocean sport and Columbia River sport 

 fisheries for all broods and years of capture. 



Assumptions 



Six assumptions are required in our method for 

 estimating contributions of hatchery fall chinook 

 salmon to the fisheries. Three basic assumptions 

 are: 1) a marked fish is identifiable as a marked 

 fish throughout life, 2) all fish detected and re- 

 ported with the kind of mark applied at the hatch- 

 eries are hatchery fish, and 3) chinook salmon are 

 correctly aged from scale examinations and in- 

 formation on size offish and date of capture. Two 

 assumptions as to the behavior of marked and 

 unmarked hatchery fish are: 4) marked and un- 

 marked hatchery fish have the same survival 



'"William G. Brown, Ashok K. Singh, and Jack A. Richards. 

 1972. Influence of improved estimating techniques on predicted 

 net economic values for salmon and steelhead. Unpubl. man- 

 user., 26 p. Oreg. State Univ., Agric. Exp. Stn., Corvallis. 



rates and maturity schedules, and 5) marked and 

 unmarked hatchery fish have the same ocean dis- 

 tribution and are equally vulnerable to the fisher- 

 ies. Finally, because part of all hatchery releases 

 bear the same mark, we assume: 6) common marks 

 were applied to the same proportion of each hatch- 

 ery's production in a given year. 



The appropriateness of the estimating proce- 

 dures is dependent on the validity of these as- 

 sumptions. Assumption 1 was tested by holding 

 marked fish in saltwater ponds for periodic 

 examination of the condition of the mark. There 

 was no regeneration of the adipose fin. However, 

 regeneration of ventral fins and maxillary bones 

 did occur. In most cases, the ventral fin regener- 

 ated to <25% of its original size. Greater regener- 

 ation was identifiable by deformation of the fin 

 rays. 



The high occurrence of maxillary regeneration 

 (7-12%) for the 1961- and 1962-brood chinook 

 salmon resulted in the removal of more of the 

 maxillary bone in the 1963- and 1964-brood fish. 

 This change in marking procedure resulted in a 

 smaller percentage offish with regenerated maxil- 

 laries (1-3%). 



Since single and double fin marks were 

 associated with maxillary clips, even when maxil- 

 laries completely regenerated, the fish were iden- 

 tifiable as marked fish. Thus we believe assump- 

 tion 1 to be true. 



The validity of assumption 2, the absence of 

 natural marks on hatchery and wild fish, was 

 tested in two ways: First, over 30 million hatchery 

 fingerlings were examined during marking for 

 naturally missing adipose and ventral fins. Only 

 156 missing adipose and 201 missing ventral fins 

 (none together) were observed indicating the in- 

 significance of naturally occurring marks on these 

 fish. Second, the occurrence of natural marks out- 

 side the hatchery system was checked by examin- 

 ing 1965-brood chinook salmon catches for study 

 marks. The allocation of study marks to any 1965 

 brood on the Pacific Coast was to have been pre- 

 vented. Unfortunately, the attempt to prevent the 

 application of study marks to this brood was not 

 completely successful. However, no adipose- 

 ventral-maxillary combinations were applied and 

 none were found in the fisheries. Any occurrence of 

 natural marks like those claimed as hatchery 

 marks has been accounted for under Estimating 

 Procedure. Therefore, we believe assumption 2 

 has been satisfied. 



Assumption 3 was evaluated by testing scale 



187 



