Adult Salmon Bioenergetics: The Cost of Migrating Upstream Through the Columbia River Hydropower System

Passage of numerous hydroelectric dams by adult spring Chinook salmon Oncorhynchus tshawytscha migrating upstream to spawning areas in the Columbia River Basin is energetically expensive and may affect their ability to reproduce.  We conducted laboratory and field investigations to estimate the total energy used by spring Chinook salmon migrating upstream through Bonneville Dam, a large hydropower dam on the Columbia River.  The laboratory study indicated that over a range of fish sizes (3.7 to 6.4 kg) and temperatures (8 to 17°C), the maximum oxygen consumption rate (about 3,350 mg O₂/h) leveled off and slightly declined at swim speeds > 170 cm/s (about 2.3 BL/s) and the upper critical swimming speed (U_crit) averaged 155 cm/s (about 2.1 BL/s).  Swim trials in the laboratory using fish outfitted with electromyogram (EMG) transmitters revealed that at about 135 cm/s, red muscle EMG pulse rates slowed and white muscle EMG pulse rates increased; 135 cm/s was about 80% of the U_crit of the fish that had EMG tags.  In the field study, spring Chinook salmon were tagged with EMG transmitters, calibrated in a swim tunnel, released below Bonneville Dam, and then tracked as they migrated through the dam’s tailrace, fishways, and forebay.  The tailrace of Bonneville Dam was the most energetically costly passage environment for these fish—they spent an average of about 21 h there and swam at an average speed of about 106 cm/s with about a quarter of the time swimming above the U_crit.  For comparison, average swim speeds in the fishways and forebay were 85 cm/s and 80 cm/s, and less than 17% of the time spent in both areas was at swimming speeds above U_crit.  The total energy used (aerobic and anaerobic) while in the tailraces was close to 48 kcal/kg, as compared to 11.1 kcal/kg in the fishways and 0.9 kcal/kg in the forebay.  Significant savings in energy use may be possible through management options that provide faster transition through tailraces and over the dam, and resting areas for adults while they are in the tailrace environment.