FURTHER STUDIES REGARDING EFFECTS 



OF TRANSPORTATION ON SURVIVAL AND 



HOMING OF SNAKE RIVER CHINOOK SALMON 



AND STEELHEAD TROUT 



Losses to juvenile and adult Pacific salmon, On- 

 corhynchus spp., and steelhead trout, Salmo 

 gairdiieri, populations migrating in the Columbia 

 and Snake rivers have increased dramatically in 

 recent years. The principal migratory route over 

 which most salmonids must pass has been ar- 

 tifically altered by construction of a series of dams. 

 The dams, with their associated reservoirs, are a 

 major source of mortality to migrating salmonids. 

 Ebel et al. (1973) summarized the primary causes 

 of mortality which include gas bubble disease, 

 turbines at dams, and predation. 



There is evidence that certain stocks of sal- 

 monids are in grave danger unless ways are found 

 to increase their populations. For example, 1973 

 returns of summer-run chinook salmon, 0. 

 tshaivi/tscha, to the Columbia and Snake rivers 

 reached all-time low proportions.' Other wild 

 stocks of steelhead trout and chinook salmon also 

 continue to decline. 



The National Marine Fisheries Service con- 

 ducted transportation experiments at Ice Harbor 

 Dam during 1968-70 to find ways of increasing 

 survival of Snake River salmonids. 



In these experiments, juvenile salmon (spring- 

 and summer-run chinook) and steelhead were 

 collected at Ice Harbor Dam and transported to 

 two locations downstream. Evaluation of these 

 tests depended upon adults returning to Ice Har- 

 bor Dam and, subsequently, to their native 

 streams. Data on adults returning from releases of 

 juvenile chinook in 1968 and of juvenile steelhead 

 in 1969 were analyzed and reported by Ebel et al. 

 (1973). Analyses of adult returns from releases of 

 juvenile chinook in 1969-70 and of juvenile 

 steelhead in 1970 are covered in this addendum 

 report. 



Methods 



General Procedures 



Migrating juvenile chinook salmon (spring- and 

 summer-run populations) and steelhead trout 

 were collected at Ice Harbor Dam by dipnet from 



gatewells (Bentley and Raymond 1969) in 1969 and 

 from a bypass collection area (Park and Farr 1972) 

 at Ice Harbor Dam in 1970. Collection from the 

 bypass area differed from dipnetting in that fish 

 were accumulated in a holding area over a 24-h 

 period. After accumulation, the fingerlings were 

 raised by a fish pump about 15 m to an aerated 

 tank truck for hauling to the fish marking facility. 

 In both years populations were mixed and ran- 

 domized before marking. The adipose fin was ex- 

 cised, a thermal brand (Mighell 1969) placed on the 

 side of the fish, and a magnetic wire tag (Jefferts 

 et al. 1963) injected into the snout of each fish. The 

 control or nontransported group was released 

 about 15 km above Ice Harbor Dam. The trans- 

 ported groups were released 5 km downstream 

 from John Day Dam on the Oregon side of the 

 Columbia River and 1 km downstream from BoTr=-\^ 

 neville Dam on the Washington side of the river 

 (Figure 1). Distinguishing brands and color-coded 

 wire were assigned to each experimental group. 



Numbers of juvenile chinook salmon and 

 steelhead trout marked and released at various 

 locations are shown in Table 1. In both 1969 and 

 1970, collection of juveniles fell below expecta- 

 tions. For example, we were able to mark only 

 28,956 chinook salmon in 1970. Therefore, numbers 

 of marked returning adults were reduced accord- 

 ingly. 



Evaluation of Returning Adults 



The effect of transportation of juveniles on 

 their survival and homing as adult fish was 

 evaluated by comparing recoveries of transported 

 and nontransported adults at various sites in the 

 river system as they returned on their spawning 



'Annual fish passage report Columbia River projects, 1973. 

 North Pacific Division, U.S. Army Corps of Engineers, P.O. Bo.x 

 2946, Portland. OR 97208. 



Figure 1. -Columbia and Snake rivers, showing release and 

 recovery sites of migrating chinook salmon and steelhead trout. 



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