THE LOW-TEMPERATURE THRESHOLD FOR PINK SALMON EGGS 

 IN RELATION TO A PROPOSED HYDROELECTRIC INSTALLATION 



Jack E. Bailey' and Dale R. Evans' 



ABSTRACT 



A proposed hydroelectric installation in southeastern Alaska would alter the seasonal pattern of stream 

 temperatures and pose a threat to the natural production of pink salmon, Oiicorhynchus gorbuscha. 

 Analysis of experiments reported in the literature indicated that such an installation might lower stream 

 temperatures below the threshold normal for the embryonic development of pink salmon. Our experi- 

 ments with pink salmon eggs incubated in refrigerated water showed that the epgs required initial 

 temperatures above 4.5° C for normal embryonic development. An increase in mortalities and in alevins 

 with spinal deformities occurred when initial incubation temperatures were 4.5° C and lower; ini- 

 tial incubation at 2° C resulted in complete mortality. The proposed hydroelectric installation could 

 result in temperatures as low as 4.5° C during spawning and initial incubation and could therefore be 

 expected to cause an increase in mortality and the occurrence of deformed alevins. The low temperature 

 would be followed by higher than normal winter incubation temperatures, which would have an unknown 

 effect on the time of emergence of fry. A tunnel intake designed to draw water of a desirable temper- 

 ature on demand would be required to protect salmon. 



In 1964 the Bureau of Reclamation (now the 

 Alaska Power Administration) started feasibil- 

 ity studies on a hydroelectric installation on Lake 

 Grace, 51 km northeast of Ketchikan, Alaska. 

 Grace Creek, the lake's outlet stream, enters the 

 sea 4 km from Lake Grace. An impassable falls 

 2 km above tide water prevents migrating fish 

 from reaching Lake Grace. Below the falls, the 

 creek provides important spawning, incubation, 

 and rearing areas for salmonids, especially pink 

 salmon, Oncorhynchus gorbuscha. 



The proposed dam would divert practically 

 all of the water from Grace Creek through a 

 hydroelectric plant and back into Grace Creek 

 about 1.2 km from tide water. Because of the 

 design of the dam and of the water intake, the 

 temperature of the lower 1.2 km of the creek 

 could be changed to lower than normal in sum- 

 mer and fall and higher than normal in winter. 



Analysis of the studies by Combs and Bur- 

 rows (1957) and Combs (1965) on the relation 

 between temperature and the development of 

 salmonid embryos indicated that when the hy- 



' National Marine Fisheries Service, Biological Lab- 

 oratory, Auke Bay, Alaska 99821. 



° National Marine Fisheries Service, Office of Water 

 Resource Studies, Juneau, Alaska 99801. 



droelectric facility is constructed, water tem- 

 peratures in the principal spawning areas of 

 Grace Creek might be too low for normal em- 

 bryonic development. We therefore estimated 

 the temperatures likely to occur in Grace Creek. 

 Because these temperatures seemed critically 

 low, we conducted laboratory experiments to de- 

 termine i^recisely the low-temperature thresh- 

 old or minimum temperature for the normal 

 development of embryos of pink salmon, the 

 major species in Grace Creek. 



In this report we analyze the effects of the 

 proposed installation on the temperature regime 

 of Lake Grace and Grace Creek and describe 

 the threshold temperatures for development of 

 ])ink salmon embryos, and then relate the two 

 studies and discuss their implications. 



EFFECTS OF PROPOSED INSTALLATION 



ON TEMPERATURE REGIME 

 OF LAKE GRACE AND GRACE CREEK 



To consider the effects of the installation on 

 the temperature regime, we compared the sea- 

 sonal temperature pattern of Grace Creek under 

 normal conditions with the temperatures likely 



Manuscript accepted February 1971. 

 FISHERY BULLETIN: VOL. 69, NO. 



587 



