FISHERY BULLETIN; VOL. 74, NO. 4 



a lower ocean survival for hatchery fry than for 

 creek fry. 



There is a notable difference in survival from 

 marking in the tests at Auke Creek and the tests 

 by Bams (1972, 1974) at Headquarters Creek, 

 Vancouver Island. The estimate of survival from 

 marking at Auke Creek, 84%, is much greater than 

 the 17% and 36% survival we estimated from 

 Bams' data on Headquarters Creek. Intertidal 

 alevin production in Auke Creek below the weir 

 was estimated by hydraulic pump survey to be 16% 

 of that above the weir. Possible straying of these 

 intertidal fish above the weir upon return would 

 only bias our estimate below actual survival from 

 marking. The slower rate at which our technicians 

 clipped fins may be the cause of better survival 

 from marking at Auke Creek. 



Our estimates of fry releases and survivals 

 imply that an increase in numbers of returning 

 spawners at Auke Creek in 1974 was largely due to 

 operation of the hatchery. If this is true, then 

 hatcheries can be built on lake-water sources with 

 a reasonable expectation of successfully enhanc- 

 ing salmon numbers. Projections of our data must 

 be considered tentative because of the lack of 

 precision. However, the magnitude of the Auke 

 Creek escapement in relation to escapements to 

 other streams in northern southeastern Alaska 

 supports our conclusion that operation of the Auke 

 Creek Hatchery did in fact enhance the return of 

 adult salmon. For example, marked hatchery fry 

 had a recovery rate of 0.767%. Survival from 

 marking was 84%. The release of 579,000 hatchery 

 fry would project to (579,000)(0.00767)/0.84 = 

 5,287 adults. The projected return of creek fry 

 would be (84,000)(0.01291)/0.84 = 1,291 adults. In 

 1974, 6,260 adults returned to the Auke Creek weir 

 from a parent escapement of 1,768 adults. This 

 3.5-fold increase occurred in the face of a general 

 scarcity of pink salmon in this part of Alaska. 

 According to Kingsbury (1975) the lowest es- 

 capement for pink salmon streams of northern 

 southeastern Alaska since 1960 occurred in 1974. 



The yolk content of fry when they leave the 

 incubating bed, either natural or artificial, bears 

 directly on the survival of the fry in the wild. Fry 

 with a large amount of yolk have not attained 

 their maximum potential size, are relatively poor 

 swimmers, may not be able to osmoregulate in 

 seawater, and are more vulnerable to predators. 

 On the other hand, fry that have little or no yolk 

 are losing weight and soon become weakened and 

 emaciated and again are more vulnerable to 



970 



predators. Naturally produced fry emerge voli- 

 tionally from the stream gravel, presumably at the 

 stage of development that ensures maximum 

 survival. Our analysis of the developmental index 

 showed our gravel incubator fry emerged prema- 

 turely in comparison to creek fry. 



Earlier (in the temporal sense) emergence of fry 

 produced in gravel incubators at Auke Creek also 

 suggests that the Auke Creek Hatchery environ- 

 ment was inferior to the natural streambed envi- 

 ronment. Hatchery fry emerged and migrated 

 seaward 2 wk earlier than creek fry. This could 

 place them in the estuary before the spring bloom 

 of zooplankton on which they feed and before 

 spring warming of estuarine surface water. The 

 resulting slow growth rate could mean an exces- 

 sively long period of high vulnerability to preda- 

 tors. Experiments by others (Levanidov 1964; 

 Bams 1967; Kanid'yev et al. 1970; Parker 1971) 

 show that small juvenile salmon suffer higher 

 mortality from predation than large juvenile 

 salmon. 



The earlier time of migration and size of hat- 

 chery fry at Auke Creek were probably caused by 

 one or more of the following: the higher average 

 winter temperature of Auke Lake water (4°C) as 

 compared to the temperature in natural redds in 

 Auke Creek (0°-2°C); the low oxygen content of 

 60-70% saturation in lake water supplied to in- 

 cubators; and the brown organic material from 

 iron bacteria which accumulated in the gravel 

 incubators and impeded the flow of water. 



ACKNOWLEDGMENTS 



We thank Joyce Gnagy, biologist at the Auke 

 Bay Fisheries Laboratory, for identifying the 

 organic growth in the gravel incubators. We also 

 thank personnel of the Alaska Department of Fish 

 and Game who reported the recovery of marked 

 fish in the sport and commercial fisheries. 



LITERATURE CITED 



Bailey, J. E., and S. G. Taylor. 



1974. Salmon fry production in a gravel incubator hatchery, 

 Auke Creek, Alaska, 1971-72. U.S. Dep. Commer., NOAA 

 Tech. Memo. NMFS ABFL-3, 13 p. 

 Bams, R. A. 



1967. Differences in performance of naturally and 

 artificially propagated sockeye salmon migrant fry, as 

 measured with swimming and predation tests. J. Fish. 

 Res. Board Can. 24:1117-1153. 



