Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 8240
Title: Responses of Snake River fall Chinook salmon to dam passage strategies and experiences
Author/Editor: Steven G. Smith, Tiffani M. Marsh, William P. Connor
Publication Year: 2018
Publisher: National Marine Fisheries Service and U.S. Fish and Wildlife Service
Contracting Agency: U.S. Army Corps of Engineers. Walla Walla, Washington
Contract Number: MIPR W68SBV20386114
Pages: 134
Date: 12/2/2014

Using releases of marked fall Chinook salmon Oncorhynchus tshawytscha, we evaluated smolt-to-adult return ratios (SARs) and other short and long-term responses to two passage strategies employed at transportation collector dams on the Snake and Columbia Rivers.   Smolt-to-adult ratios from detections of subyearlings released in 2006 and 2008-2012 suggest that adult returns would be maximized using a management strategy of bypassing fish collected in juvenile bypass systems early in the season and transporting fish collected fish later in the season at Lower Granite, Little Goose, and Lower Monumental Dam.  Based on a grand geometric mean of T:B ratios (transport-to-bypass) for surrogate and production subyearling types combined (weighting the two types equally) at the three dams for which we calculated model-averaged daily estimates, the best day for starting transportation would be on or near 1 July.

Data for McNary Dam were not sufficient to determine within-season patterns satisfactorily.  However, annual totals for McNary Dam showed a large advantage for transported subyearlings.  These annual totals, combined with the consistent pattern of increasing survival for fish transported later in the season at each of the other dams, suggest that transportation from McNary Dam likely led to higher SARs for fish arriving later in the season and possibly for those arriving earlier as well.

The methods of analysis and results reported here are novel and represent extensive development of our analytical approach for over a decade, beginning with the first transportation studies of juvenile fall Chinook salmon in 2001. 



Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.