BAILEY ET AL.: PRODUCTION OF FRY AND ADULTS AT AUKE CREEK 



Table 4.-Average lengths of adult pink salmon returning to 

 Auke Creek weir, early and late runs; the figures in parentheses 

 represent the number of fish in the samples. 



Average lengths (mm) 



Early run 



Late run 



Mark 



Origin 



Male Female 



Male Female 



'Ad-LV = adipose and left ventral fins. 

 ^Ad-RV = adipose and right ventral fins. 



ances, probably because of the small sample sizes. 

 Differences in length due to origin, time of 

 return, or interaction were not detectable at the 

 95% level of testing for either sex (Table 5). Only 

 time of return for females approached statistical 

 significance (the test would have been significant 

 at the 90% level). Mean lengths of samples of creek 

 fish exceeded those of hatchery fish in all cases 

 (Table 4). While our data suggest that creek fish 

 were larger than hatchery fish upon return, the 

 observed differences could be due to chance when 

 samples were drawn. Larger samples would have 

 been needed to resolve the issue. 



Table 5.-Analysis of variance of size of returning adult male 

 and female pink salmon classified by origin (creek or hatchery) 

 and time of return (early or late). 



Timing of Adult Return 



Marked hatchery fish entered the weir between 

 6 August and 25 September and marked creek fish 

 entered between 16 August and 20 September 

 (Figure 8). For 644 marked hatchery fish the 

 median date of return was 13 September 1974; for 

 71 marked creek fish the median date was 10 

 September. 



DISCUSSION 



Gravel incubation of eggs and release of unfed 



T — I — I — r 



10 15 20 25 

 AUG. 



T — I — I — r 



10 15 20 25 



SEPT. 



Figure 8.-Daily cumulative percentage recovery of marked 

 adult pink salmon at Auke Creek weir, 1974. 



fry increased the survival from potential egg 

 deposition to returning adult an estimated 5 to 6 

 times over natural spawning for 1972 brood year 

 pink salmon at Auke Creek. The estimate lacks 

 precision, however, and a rough 95% confidence 

 statement includes the possibility that egg-to-re- 

 turning-adult survival was less for incubator fry 

 than for naturally produced fry. Further, the 

 estimate of relative survival is potentially biased 

 unless marine mortality due to marking and 

 fishing was similar for both groups of marked fry. 

 The similarity of timing of adult returns from 

 both groups gives no reason to suspect differential 

 fishing mortality. The low mortality of creek fry in 

 the fyke net and live-box suggests only slightly 

 greater physical abuse occurred to marked creek 

 fry than hatchery fry. The difference in survival 

 from potential egg deposition to returning adult, 

 if real, was accomplished in spite of certain 

 deficiences in the quality of environment provided 

 for eggs and alevins in the hatchery and in spite of 



969 



