WAHLE and VREELAND: BIOECONOMIC CONTRIBUTION OF FALL CHINOOK SALMON 



returned to these facilities and were spawned dur- 

 ing September and October. Fry reached free 

 swimming stage in February or March and were 

 then placed in ponds. They were reared 90 to 120 

 days in the hatchery and released at an average 

 length of 6 to 8 cm (2-3 in). Since there was consid- 

 erable variation in time and size of release be- 

 tween hatcheries and brood years, we have in- 

 cluded Table 5 to complete the release procedure 

 record. After the hatchery fall chinook salmon 

 spent 1 to 6 yr in the ocean, where they were 

 available to sport and commercial fisheries from 

 southeastern Alaska to central California, they 

 matured and returned to the Columbia River. 



The marking phase of this study extended from 

 June 1962 through June 1965. Approximately 

 10*7^ of the 1961-64 broods were marked. A "10- 

 part sampler," a modified sampling tool (Worlund 

 et al. 1969), was used to obtain the sample offish 

 for marking. The sampler consisted of a cylindri- 

 cal liner containing a circular metal frame. The 

 frame was divided into 10 equal pie-shaped sec- 

 tions with a zipper-bottomed net pocket hung from 

 each section. To obtain a sample for marking, the 

 zippers on one or more pockets were closed, the 

 frame and liner were placed in a water-filled tub, 

 and 18 kg (40 lb) offish were placed into the liner. 

 The closed pocket, or pockets, retained the desired 

 sample when the liner and frame were lifted. The 

 fish remaining in the tub were placed into another 

 pond. This procedure was followed until all 

 chinook salmon in each pond were processed. In 

 the case of the special mark hatcheries, two or 

 more pockets were closed. One pocket retained the 

 fish for common marking and the other pockets 

 retained those for special marking. The intention 

 was to apply special marks to between 500,000 and 

 1.0 million chinook salmon at each of the special 



mark hatcheries. We felt this number would pro- 

 vide a statistically sound number of special mark 

 recoveries for each hatchery. The hatchery man- 

 ager's estimate of the number of fall chinook salm- 

 on on hand at the time of sampling was used to 

 determine how many pockets to close at each 

 hatchery to obtain the desired sample for special 

 marking. These estimates were sometimes inac- 

 curate, resulting in a smaller or larger sample 

 than had been desired. 



Fish to be marked were anesthetized with 

 MS-222 (tricaine methanesulfonate). The fins and 

 maxillary bones were clipped with bent-nosed 

 scissors. Marked fish were held in hatchery 

 troughs until they recovered from the anesthetic, 

 then returned to the group of unmarked fish from 

 which they came. Mark quality control was main- 

 tained by sampling 100 marked fish per marker at 

 irregular periods each day and grading them ac- 

 cording to quality of mark. Each year over 100,000 

 marked fish were sampled and graded. This grad- 

 ing indicated a high mark quality was attain- 

 ed. 



The entire production of fall chinook salmon at 

 the study hatcheries was sampled with the 10-part 

 sampler prior to release to estimate the marked 

 and unmarked releases. The "107c" samples were 

 set aside and resampled to obtain a "1%" sample 

 which was sorted into marked and unmarked 

 groups, counted, and weighed. The counts and the 

 estimate of the proportion removed by the particu- 

 lar sampler were used to estimate the numbers of 

 marked and unmarked fish released. 



Over 213 million 1961-64-brood fall chinook 

 salmon were released from the study hatcheries. 

 Of these, 21.3 million were given the common 

 mark and 9.6 million were given a special mark 

 (Table 1). 



Table 5. — Size and date of release of 1961-64 broods of fall chinook salmon from Columbia River 

 hatcheries participating in the fall chinook salmon study by hatchery and brood. 



'Fish per pound. 



189 



