WAHLE. VREELAND, and LANDER: BIOECONOMIC CONTRIBUTION 



Table 2. — Estimated numbers, percentage marked, and marked to unmarked ratios of 1965- and 1966- 

 brood coho salmon released from evaluation hatcheries by river sections. 



1/ Released below Bonneville Dam. 



sons were stratified into relatively small time 

 units (usually 2-\vk periods). 



The main fisheries sampled were ocean sport 

 and commercial, Columbia River sport and 

 commercial, and Puget Sound fisheries. The 

 ocean fisheries were stratified further by port of 

 landing. The Alaska and British Columbia troll, 

 purse seine, and gillnet fisheries; Columbia 

 River commercial and sport fisheries; and Puget 

 Sound sport and commercial fisheries were 

 stratified by area of catch. The specific fisheries 

 sampled are listed in Table 3 and shown in 

 Figure 2. 



Catch data for each time-location stratum 

 were provided by management agencies. The 

 catch of coho salmon in numbers of fish was an 

 estimate for most fisheries. Commercial catches 

 were estimated either from (1) the total weight 

 of landings and an estimate of average fish size 

 or (2) total salmon landings (numbers) and an 

 estimate of species composition. Estimates of 

 sport catches were from measures of total 

 effort and catch per unit of effort or from salm- 

 on punch cards together with independent 

 sampling by the management agency. 



About 20% of each time-location stratum 

 was sampled for marks. Table 4 gives the annual 



total catch of both broods of coho salmon by 

 year and number sampled for marks each year. 

 During the 3 years of sampling, 15.4% of the 

 total catch of 21.1 million coho were examined 

 for marks. The actual mark sampling percent- 

 ages were 18.3, 13.5, and 14.3% for 1967, 

 1968, and 1969, respectively. 



Enumeration of Returns to Hatcheries 



An estimate of the numbers returning to 

 hatcheries was required to measure the total 

 hatchery output and marking mortality. All 

 returns to most hatcheries were e.xamined for 

 marks; at some hatcheries, the numbers marked 

 and unmarked were calculated after a known 

 percentage of the total return was sampled for 

 marks. A breakdown of the returns to each of 

 the study hatcheries is in Appendix Tables 2a 

 and 2b. 



Estimation of Total Catch 

 from Hatcheries 

 Actual Recoveries 



Tables 5a and 5b summarize marked recov- 

 eries by brood year, mark, year of recovery, 



145 



