In spring 1996 and 1997, we studied the prototype surface bypass and collector (SBC) at Lower Granite Dam on the Snake River in Washington. Our objectives were to determine the most efficient SBC configuration and to describe smolt movements and swimming behavior in the forebay. To do this, we used hydroacoustic and radiotelemetry techniques. The SBC was retrofitted onto the upstream face of the north half of the powerhouse to test the surface bypass method of diverting smolts from turbines. The SBC had three entrances, with mean velocities ranging from 0.37 to 1.92 m/s, and it discharged 113 m3/s through its outlet at Spill Bay 1, which was adjacent to the powerhouse. Different SBC configurations were created by altering the size and shape of entrances. During spring 1996 and 1997, river discharge was well above normal (123 and 154% of average, respectively). Powerhouse operations caused a strong downward component of flow upstream of the SBC. Many smolts (primarily steelhead and secondarily chinook salmon) were observed actively swimming upward in the water column. There were four times as many smolts diverted from turbines per unit volume of water with SBC flow than with spill flow, which indicated that the SBC may be an especially important bypass consideration in moderate- or low-flow years. The highest SBC efficiency (the proportion of total fish passing through the north half of the powerhouse by all routes that passed through the SBC) for any configuration tested was about 40%. Although no single SBC configuration stood out as the most efficient, the horizontal surface and maximum area configurations, or some combination of the two, are worth further investigation because they were moderately efficient.

Washington↗

USGS2000

Identification of juvenile fall versus spring chinook salmon migrating through the lower Snake River based on body morphology

We tested the use of body morphology to distinguish among subyearling fall-run, subyearling spring-run, and yearling spring-run smolts of chinook salmon Oncorhynchus tshawytscha at two lower Snake River dams during the summer emigration. Based on principal-components analysis, subyearling fall-run chinook salmon had smaller heads and eyes, deeper bodies, and shorter caudal peduncles than yearling spring-run chinook salmon. Subyearling spring-run chinook salmon had characteristics of both subyearling fall-run and yearling spring-run chinook salmon. Subyearling fall-run and yearling spring-run chinook salmon were classified with more than 80% accuracy by means of discriminant analysis. Classification accuracy for subyearling spring-run chinook salmon was only 26%. We conclude that body morphology can be used to accurately identify the age of chinook salmon smolts but not the run. Therefore, genetic analyses are the only means of reliably determining the run composition of summer migrants in the lower Snake River.

Transactions of the American Fisheries Society↗

USGS2000

Physiological development and migratory behavior of subyearling fall chinook salmon in the Columbia River

We describe the migratory behavior and physiological development of subyearling fall chinook salmon Oncorhynchus tshawytscha migrating through John Day Reservoir on the Columbia River, Washington and Oregon. Fish were freeze-branded and coded-wire-tagged at McNary Dam, Oregon, from 1991 to 1994, to determine travel time to John Day Dam and subsequent adult contribution. Stepwise multiple regression showed that 47% of the variation in subyearling fall chinook salmon travel time was explained by the reciprocal of minimum flow and fish size. Smoltification, as measured by gill Na+-K+ adenosine triphosphatase (ATPase) activity, was not important in explaining variability in travel time of subyearling chinook salmon. Fish marked early in the out-migration generally traveled faster than middle and late migrants. Seawater challenges were used to describe physiological development and showed that osmoregulatory competence of premigrants in the Hanford Reach of the Columbia River increased with fish size and gill ATPase activity. Once active migrants began passing McNary Dam, fish generally had survival exceeding 90% and were able to regulate their blood plasma Na+ in seawater. Gill ATPase activity increased as premigrants, reared in nearshore areas of the Hanford Reach, reached a peak among active migrants in late June and early July then decreased through the remainder of the out-migration. Salinity preference also peaked in subyearling fall chinook salmon during late June to mid July in 1995. Return of adults from marked groups showed no consistent patterns that would suggest a survival advantage for any portion of the juvenile out-migration. Presumed wild migrants from the middle and late portions of the out-migration were primary contributors to all fisheries, except the Priest Rapids Hatchery. As such, fishery managers should take action to ensure the survival of these fish, especially because they migrate under more unfavorable environmental conditions than early migrants.

Oregon; Washington↗

USGS2000

Migratory behavior and forebay delay of radio-tagged juvenile fall chinook salmon in a lower snake river impoundment

During July and August 1995-1997, we used radiotelemetry to estimate the migration rate of 405 juvenile fall chinook salmon Oncorhynchus tshawytscha (mean fork length, 138-144 mm) through Little Goose Reservoir. Migration rates decreased significantly as fish approached the dam. Median migration rates in 1995 were 26.0 km/d through the 45.9-km reach immediately below Lower Granite Dam, 14.9 km/d through the next 14.4 km, and 0.8 km/d in the Little Goose Dam forebay (0.6 km). Median migration rates through the same reaches were consistent among years: 24.8, 13.4, and 0.8 km/d in 1996 and 20.2, 10.2, and 1.0 km/d in 1997. Most fish migrated through the upper 45.9 km within 5 d and through the lower two reaches (15.0 km) within an additional 5 d. However, 10% to 20% of the fish spent a week or more in the forebay and lower reservoir. Radio-tagged smolts displayed two behaviors after entering the forebay: crossing the forebay and upstream excursions. Study fish crossed the forebay an average of 0.6-1.0 time/h, and 157 upstream excursions were identified, 15 of which were at least 14.4 km in length. Fish behavior in the forebay was associated with declining water velocities near the dam. Detections of passive integrated transponder tags suggest that similar delays occur in other lower Snake River reservoirs. Based on studies from the Columbia River, delays for 20% of the juvenile fall chinook salmon outmigrants in each of these forebays may have contributed to high predation losses and pose a serious challenge to efforts aimed at restoring this threatened salmon stock.

Washington↗

USGS2000