WAHLE ET AL 1960-63 BROOD HATCHERY-REARED SOCKEYE SALMON 



Under the Grand Coulee Fish-Maintenance 

 Project, sockeye salmon adults were trapped in 

 July and August and hauled by tank truck to Lake 

 Wenatchee, 113 km above Rock Island Dam, 

 where a barrier was installed at the outlet. When 

 spawning time approached, the fish ascended the 

 White and Little Wenatchee Rivers where they 

 spawned. When eggs were later needed for hatch- 

 ery use, weirs were installed and adults trapped to 

 supply the required ova. Surplus adults were al- 

 lowed to pass upstream and spawn naturally. The 

 offspring of these natural spawners homed back to 

 the system to establish the new Wenatchee stock. 



Spawning occurred in September and October. 

 The fry emerged from the gi-avel in spring and 

 drifted back down to the lake to rear until the 

 following year. Outmigration occurred in April 

 and May, with a peak reached in early May prior 

 to the heavy spring run-off period (French and 

 Wahle 1959). Following 2, or occasionally 1 or3,yr 

 at sea, the adults entered the Columbia River in 

 late spring. The run passed Bonneville Dam in 

 late June and early July, and several weeks later 

 ascended the Wenatchee River to renew the cycle. 



The Hatchery 



Leavenworth National Fish Hatchery was com- 

 pleted in 1940 as the primary station to provide 

 hatchery-reared fish to supplement the newly es- 

 tablished natural runs. Sockeye salmon were to be 

 produced there and adults of other species were 

 spawned to obtain stock to supply the satellite 

 stations on the Entiatand Methow Rivers (Figure 

 2). The hatchery capacity was approximately 3.5 

 million eggs and 2.4 million fingerlings (Fish and 

 Hanavan 1948). 



The source of eggs for the first 5 yr of operation 

 was fish that had been hauled to Lake Wenatchee 

 from Rock Island Dam as part of the relocation 

 project. After this period the adult transportation 

 was terminated and spawning operations con- 

 tinued using fish returning to the lake naturally. 



After the eggs were taken and fertilized, usually 

 in September, they were transferred to the hatch- 

 ery for incubation. Hatching began in January 

 and the fry began to feed about 6 wk later. Initial 

 rearing took place inside the hatchery, and when 

 water temperatures became suitable, they were 

 placed in outside rearing ponds. In September or 

 October, upon reaching an average weight of 9 to 

 10 g, the fingerlings were trucked to the lake. 



Survival from egg to stage at release ranged from 

 62 to 967f . After winteringover until the following 

 April or May, the smolts migrated out of the lake. 



From general observations, it appeared that the 

 hatchery operation was a success: proper rearing 

 techniques were followed, hatchery migrants were 

 observed leaving the lake, adults returned to the 

 area in adequate numbers, and fish were available 

 for commercial harvest. Data obtained through 

 spawning surveys and downstream migrant 

 counts at the dams indicated that the sockeye 

 salmon population was being satisfactorily main- 

 tained. However, it was not possible to determine 

 whether the wild stock or the hatchery fish con- 

 tributed most to the runs. Downstream migrant 

 studies by Anas and Gauley 1 1956 1 pointed out the 

 impossibility of identifying the separate stocks. 



There were indications that the costs of conduct- 

 ing a sockeye salmon hatchery program were sig- 

 nificantly higher than the values contributed to 

 the fishery. Despite complexities of measurement 

 of runs, some means of assessment seemed neces- 

 sary. Thus, a study was designed to evaluate the 

 economic feasibility of continuing artificial propa- 

 gation of sockeye salmon at the hatchery. 



The study involved the marking of a proportion 

 of the hatchery sockeye salmon production for a 

 period of 4 yr, observations on the rearing and 

 migration of the fingerlings, and estimation of the 

 contribution of returning adults to the commercial 

 fishery. An analysis of production costs and the 

 monetary benefits to the fishermen was included. 



FIELD OPERATIONS 



Estimating Procedures 



The procedures used in making estimates of 

 numbers offish are similar to those described in 

 reports by Worlund et al. (1969) and Wahle et al. 

 (1974). Estimates of the potential contributions 

 and value of hatchery sockeye salmon required 

 four steps: 1) estimation of marked and un- 

 marked hatchery releases, 2) estimation of catch 

 of marked adults, 3) estimation of total contribu- 

 tion of hatchery fish to the catch, and 4) applica- 

 tion of dollar values to the estimate of contribu- 

 tion. 



Marking and Release Procedure 



The study began in July 1961, using 1960-brood 

 fingerling sockeye salmon. Each year, approxi- 



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