EFFECTS OF TRANSPORTATION ON SURVIVAL 



AND HOMING OF SNAKE RIVER 

 CHINOOK SALMON AND STEELHEAD TROUT 



Wesley J. Ebel, Donn L. Park, and Richard C. Johnsen* 



ABSTRACT 



The homing abihty of adult fish that were captured during their seaward migration 

 as juveniles and then transported downstream (from Ice Harbor Dam to Bonneville Dam) 

 was not diminished. Data from returning adults indicated survival of adult fish that 

 had been transported downstream as juveniles was higher than that of fish not trans- 

 ported. The percentage of increased survival ranged from 50 to 30^^^ depending on the 

 river environment during the time of transport. Information on the timing of the 

 seaward migration and the extent of mixing of seaward runs of spring and summer 

 Chinook salmon, Oncorhynchus tsluiwyischa, was also obtained. 



Losses to juvenile and adult Pacific salmon, 

 Oncorhynchus spp., and steelhead trout, Sahno 

 gairdnen, populations migrating in the Colum- 

 bia and Snake Rivers have increased drastically 

 in the last decade because of the effects of 

 recently completed dams. The reservoirs formed 

 by these dams have inundated some important 

 spawning and rearing areas, have created new 

 passage problems for both adult and juvenile 

 migrants, and, in most cases, have significantly 

 changed the aquatic environment to the detri- 

 ment of salmonid fishes. 



Gas bubble disease caused by high concen- 

 trations of dissolved nitrogen gas, resulting 

 from the spilling of water at dams, has been 

 pinpointed by the National Marine Fisheries 

 Service (NMFS) (Ebel, 1969; Beiningen and 

 Ebel, 1970; Ebel, 1971) as a major cause of 

 salmon and steelhead trout mortalities. Nitro- 

 gen gas in the atmosphere is forced into solu- 

 tion as the water plunges into deep spill 

 basins; the dissolved gas remains in solution 

 in impounded sections of the river resulting 

 in several hundred kilometers of water super- 

 saturated with nitrogen gas through which 

 fish must migrate. Another significant source 

 of mortality can be due to passage of fish 



' Northwest Fisheries Center, National Marine Fish- 

 eries Service, NOAA, 2725 Montlake Boulevard East, 

 Seattle, WA 98112. 



through turbines, particularly when indirect 

 mortalities due to predation on fish emerging 

 from turbines are included. These mortalities 

 will persist even if nitrogen levels are reduced. 

 Recent estimates (Raymond, 1970)- of losses 

 to juvenile populations migrating downstream 

 in the Snake and Columbia Rivers — that 

 reflect losses from all sources, including nitro- 

 gen supersaturation — indicate that chinook 

 salmon, O. tsliairytscho, and steelhead trout 

 from the upper Snake River drainage may be 

 reduced to critically low numbers unless action 

 is taken to reduce these losses. 



NMFS has been conducting transportation 

 experiments since 1965 to find ways of reducing 

 these losses. Since 1968 we have been con- 

 centrating on an experiment where migrating 

 juvenile salmon and trout — mostly spring 

 and summer chinook salmon — are collected 

 at Ice Harbor Dam and transported to two 

 locations downstream. The experiment was 

 designed to determine the effect of transpor- 

 tation on survival and homing. 



Past information (Ellis and Noble, 1960; 

 unpublished hatchery records of Washington, 



Manuscript accepted September 1972. 

 FISHERY BULLETIN; VOL. 71, NO. 2, 1973. 



- Raymond, H. L. 1970. A summary of the 1969 

 and 1970 outmigration of juvenile chinook salmon and 

 steelhead trout from the Snake River, Progress Report. 

 U.S. Dep. Commer., Natl. Oceanic Atmos. Admin., 

 Natl. Mar. Fish. Serv., Biol. Lab., Seattle, Wash. Unpubl. 

 manuscr. 



549 



