recorded. Scales were taken for age determina- 

 tion. Age determinations of fish returning to the 

 hatchery in previous years had indicated the size 

 range for 2-yr-old jack salmon, but 3- and 4-yr-old 

 fish could not be separated by size. During the 1966 

 spawning season, a vertebra was removed from all 

 fish smaller than the maximum length previously 

 found for 2-yr-old fish, for determination of tet- 

 racycline marks. During the 1967 and 1968 

 spawning seasons, a vertebra was also removed 

 from all fish in the size range of previous 3- and 

 4-yr-old fish. 



Vertebrae were scanned under ultraviolet light 

 by the technique described by Weber and Ridgway 

 (1962). Vertebrae with tetracycline marks were 

 classified as hatchery fish. The age of fish without 

 vertebra marks was determined by examination 

 of the scales. All unmarked fish of the correct age 

 were considered to be recoveries from either the 

 channel or creek. Tetracycline bands were visible 

 in the vertebrae of all fin-clipped salmon. 



Adult returns from two sources— the hatchery or 

 Abernathy incubation channel and Abernathy 

 Creek— were determined by measuring and aging 

 fish and by identifying those with fin clips and 

 tetracycline marks on vertabrae. Potential egg 

 production was calculated on the basis of 5,000 

 eggs per female, the average number found in 

 Chinook salmon returning to the hatchery in 

 previous years. 



RESULTS 



FISHERY BULLETIN: VOL. 73, NO. 2 



only 20 returned. Disease and parasite problems 

 encountered during the summer rearing season 

 probably contributed to the low survival. Fish 

 released before the warm-water season appeared 

 to have better survival. The total survival was 

 0.070%. 



Adult Returns from 

 Abernathy Incubation Channel and Creek 



The percentage returns of fish from the Aber- 

 nathy incubation channel (0.016%) was considera- 

 bly lower than that from the hatchery (Table 3). 

 The higher ratio of female fish, however, resulted 

 in a relatively higher number of eggs per return- 

 ing fish. 



The numbers of returning fish that originated in 

 Abernathy Creek were insignificant. If the sur- 

 vival rate after migration is assumed to be iden- 

 tical for channel and creek migrants, only 0.36% of 

 the 736 returning unmarked adults— or about 3 

 fish— were from the creek. 



Table 3.-Number of male and female adult chinook salmon re- 

 turns from 4,620,600 fry released at the Abernathy incubation 

 channel, 1965. 



Age at return 

 (years) 



Males 



Females 



Potential egg production 

 (thousands) 



2 

 3 

 4 



Total 



16 

 202 

 107 



325 





 220 

 188 



408 







1,100 



940 



2,040 



Adult Returns from 

 Hatchery- Reared Fingerlings 



Table 2 presents adult return data for both 1) 

 the fin-clipped plus tetracycline-marked group and 

 2) the tetracycline-marked groups. Survival of fish 

 that had been marked with both tetracycline and 

 fin clip was low; of 161,579 fingerlings released, 



Table 2.-Number of male and female adult chinook salmon re- 

 turns from 719,228' hatchery-reared fingerlings released from 

 the Salmon-Cultural Laboratory hatchery, 1965. 



Age at return 

 (years) 



Males 



Females 



Potential egg 

 production 

 (thousands) 



2 

 3 

 4 



Total 



209 

 90 

 34 



333 





 96 

 77 



173 





 480 

 385 



865 



'Of this total, 557,649 fish were released with tetracycline bands 

 and 161,579 with double fin clips and tetracycline bands. 



DISCUSSION 



Survival was low from chinook salmon of the 

 1964 year class released from most Columbia River 

 hatcheries, as they were in this experiment. 

 Reasons for the poor survival are largely un- 

 known. Although the evaluation of survival from 

 several year classes would have been desirable, 

 comparisons of survival from the different sources 

 of young fish provide information on the relative 

 survival of channel-reared and hatchery-reared 

 fish, as well as an insight into the potential sur- 

 vival from an incubation channel. Ideally, 

 sufficient adults should return to a salmon 

 hatchery to provide 100% or more of the original 

 egg supply. Assuming about 5,000 eggs per female 

 and a 50:50 ratio of males to females, a chinook 

 hatchery is self-sustaining when the return is 

 about 0.045%. 



358 



