WAHLE and VREELAND: BIOECONOMIC CONTRIBUTION OF FALL CHINOOK SALMON 



was precalibrated from a number of trials with 

 known numbers of fish to find the average per- 

 centage retained by a single closed pocket. The 

 following example illustrates the fish enumera- 

 tion procedure for a pond of fall chinook salmon. 

 Suppose a precalibrated pocket is found to remove 

 a 10.1'7f sample. Also, suppose after passing all 

 the fish in a pond through the sampler, the number 

 offish retained by the closed pocket is found to be 

 20,200. The total number of fish in that pond is 

 then estimated as 20,200 0.101 = 200,000. Sup- 

 pose further that of the 20,200 fish retained in the 

 pocket, 2,020 fish are found to be marked. Then 

 2,020/20,200 = 10% of the estimated 200,000 fish 

 in the pond, or 20,000 are estimated to be marked 

 and 180,000 unmarked. The total release, num- 

 bers marked ( common and special ) and unmarked, 

 were estimated for a hatchery by summing data 

 from all ponds. 



Catch of Marked Fish 



To estimate the catch of marked fish in a given 

 area and fishery, the following values were needed 

 by time period: total catch; number of fish 

 examined for marks; number of marked fish by 

 species, mark type, and age; and the proportion of 

 each age-group in the total catch. The sampling 

 seasons were stratified into relatively small time 

 units (usually 2-wk periodsK The estimated 

 catches of a particular mark were summed over 

 the entire fishing season for a given area and 

 fishery. For example, during the period from 26 

 June through 9 July 1966 in the Ilwaco sport 

 fishery, 1,193 chinook salmon from a total catch of 

 5,664 were examined for marks, for a 21.1% sam- 

 ple. Samplers found one Ad-LM marked 1964- 

 brood (2-yr-old) fall chinook salmon during this 

 period. Then the estimated catch of 1964-brood 

 Ad-LM marked fall chinook salmon during this 

 period was 1/0.2106 = 5. Catches of 1964-brood 

 Ad-LM marked chinook salmon for the Ilwaco 

 sport fishery in 1966 were summed for 13 time 

 periods. This resulted in an estimated catch of 196 

 Ad-LM marked fish. 



This procedure was carried out for each port 

 sampled and each mark found. Catch data for each 

 time-location stratum were provided by manage- 

 ment agencies. Commercial catches were esti- 

 mated from total landing weights and average fish 

 size data or from total numbers of salmon landed 

 and species composition estimates. Sport catches 

 were estimated from measures of total effort and 



catch-per-unit-efTort or from salmon punch cards 

 and independent sampling. All catch and sampl- 

 ing information was transferred to computer cards 

 and estimates were calculated by computer. Un- 

 published reports of catch and mark data were 

 produced for 1963 through 1969 by the Seattle 

 Biological Laboratory, Bureau of Commercial 

 Fisheries (now the Northwest and Alaska 

 Fisheries Center, National Marine Fisheries Ser- 

 vice, NOAA). 



Contribution of Hatcher) Fish 



Maxillary regeneration occurred during the 

 ocean lives of some of the common and special 

 marked chinook salmon, resulting in partial 

 marks (see Assumptions). For example, a 1961- 

 brood Kalama Ad-RV-RM mark could have regen- 

 erated to an Ad-RV mark, or a 1962-brood Ad-LM 

 common mark could have regenerated to an Ad- 

 only mark. Partial marks were a result of this 

 regeneration and/or an occurrence of naturally 

 marked fish. If partial marks due to regeneration 

 were not claimed as part of the marked hatchery 

 fish total, the hatchery contribution would be un- 

 derestimated considerably. Therefore, we 

 examined the ocean catches of chinook salmon 

 with partial marks to determine the number that 

 could be claimed as hatchery fish. 



A comparison of maxillary regeneration rates of 

 marked fish held at Bowman Bay (Worlund et al. 

 1969) and the occurrence of Ad-SV (adipose-single 

 ventral ) and Ad-only partial marks in the fisheries 

 (Table 2), led us to believe Ad-LV, Ad-RV, and 

 Ad-only marks occurred because of maxillary re- 



TabLE 2. — Percent partial mark occurrence in the ocean and 

 Columbia River fisheries and in hatchery returns, 1961-64 

 broods. 



' Figures are ratios, averaged for all years by brood, of estimated numbers of 

 partial marks to estimated sum of partial marks and corresponding complete 

 marks expressed in percent. 



^SV signifies single ventral." Marks of same general type are combined. 



183 



