3 



o 



o 

 o 



o 



z 



o 



z 



1 2 3 4 5 6 e 10 15 20 30 40 50 60 



POUNDS OF FINGERLINGS RELEASED AT SPRING CREEK ON A LOG SCALE (THOUSANDS) 



Figure 6. --Cor relation between fingerling release (in pounds) at Spring Creek 

 Hatchery and adjusted return of females as explained in appendix table 9. 



Hatchery stock were reared at Spring Creek 

 Hatchery but released in Big White Salmon 

 River. Ricker (1959)" lists a number of ex- 

 amples where similar transplants produced 

 few returns, and although Spring Creek 

 Hatchery stocks were originally from Big 

 White Salmon River, it is not unlikely that 

 returns from such a transplant would be 

 greatly reduced either from straying or in- 

 creased mortality. 



Relationship Between Fingerling Releases 

 and Returns for Brood Years 1949-55 and 

 Indications of Reduced Survival Rate in 

 Recent Years 



In 1950, 3 raceways were added at Spring 

 Creek Hatchery and 10 circular ponds were 

 installed. In figure 6 adjusted returns of 

 females to Spring Creek Hatchery are plotted 



^ W, E. Ricker, "Evidence for environmental and 

 'genetic influence on certain characters which distin- 

 guish stocks of the Pacific salmons and steelhead 

 trout." Unpublished manuscript. Fisheries Research 

 Board of Canada. 1959. 



against pounds (graphed on logarithmic scale) 

 of fingerlings released at Spring Creek 

 Hatchery for the brood years 1941-55. Follow- 

 ing each increase in rearing capacity, there 

 was an increase in the pounds of fingerlings 

 reared. The brood years represented in figure 

 6 are therefore conveniently separated accord- 

 ing to available capacity. 



The reduction in return per pound of finger- 

 lings released since 1950 is very marked, 

 particularly when the effects of the logarithmic 

 scale on pounds released are taken into ac- 

 count! For example, for the 1945, 1946, and 

 1947 broods total releases of about 10,000 

 pounds produced an adjusted return of about 

 7,000 females, whereas for the 1954 and 1955 

 broods (representing the record-producing re- 

 turns of 1958 and 1959) almost eight times as 

 many pounds of fingerlings (about 80,000 

 pounds) produced less than twice the returns 

 (about 12,000 females). If the returns in 1958 

 and 1959 involved significantly more 3-year- 

 olds, the actual production for the 1954 and 

 1955 broods may be little better than is in- 

 dicated for the brood years 1950-53. 



11 



