Howard L. Burge

Influence of Flow and Temperature on Survival of Wild Subyearling Fall Chinook Salmon in the Snake River

Abstract Summer flow augmentation to increase the survival of wild subyearling fall chinook salmon Oncorhynchus tshawytscha is implemented annually to mitigate for the development of the hydropower system in the Snake River basin, but the efficacy of this practice has been disputed. We studied some of the factors affecting survival of wild subyearling fall chinook salmon from capture, tagging, and release in the free-flowing Snake River to the tailrace of the first dam encountered by smolts en route to the sea. We then assessed the effects of summer flow augmentation on survival to the tailrace of this dam. We tagged and released 5,030 wild juvenile fall chinook salmon in the free-flowing Snake River from 1998 to 2000. We separated these tagged fish into four sequential within-year release groups termed cohorts (N = 12). Survival probability estimates (mean ± SE) to the tailrace of the dam for the 12 cohorts when summer flow augmentation was implemented ranged from 36% ± 4% to 88% ± 5%. We fit an ordinary...

Juvenile Life History of Wild Fall Chinook Salmon in the Snake and Clearwater Rivers

Abstract Dam construction in the 1950s and 1960s blocked passage to the historical spawning area of Snake River fall chinook salmon Oncorhynchus tshawytscha. We obtained water temperature data and collected juvenile fall chinook salmon in three present-day spawning areas from 1992 to 2000 to investigate the relation between water temperature and juvenile life history events. We used historical water temperatures and the literature to depict juvenile life history in the historical spawning area. Water temperatures in the three present-day spawning areas differed significantly from winter to spring, when eggs were incubating (P ≤ 0.0001), as well as during spring, when juveniles were rearing and starting seaward migration (P ≤ 0.0001). When water temperatures were warmer, the timing of most life stages was generally earlier. The life stages included fry emergence (r 2 = 0.85, N = 14, P < 0.0001), growth to parr size (r 2 = 0.94, N = 15, P < 0.0001), and smolt emigration (r 2 = 0.93, N = 14, P < 0.0001). The...

Migrational Behavior and Seaward Movement of Wild Subyearling Fall Chinook Salmon in the Snake River

Abstract Flow augmentation increases flow and decreases temperature in reservoirs in the lower Snake River during the seaward migration of wild subyearling fall chinook salmon Oncorhynchus tshawytscha. A study of the migrational behavior and seaward movement of wild subyearling fall chinook salmon in the Snake River was necessary to help understand the efficacy of flow augmentation. We studied fall chinook salmon in the Snake River during 1992–2001. After analyzing mark–recapture data, we deduced that fall chinook salmon passed through at least four migrational phases, including (1) discontinuous downstream dispersal along the shorelines of the free-flowing river, (2) abrupt and mostly continuous downstream dispersal offshore in the free-flowing river, (3) passive, discontinuous downstream dispersal offshore in the first reservoir encountered en route to the sea, and (4) active and mostly continuous seaward migration. We used ordinary-least-squares multiple regression to test the effects of flow (m3/s), t...

Detection of PIT-tagged subyearling Chinook salmon at a Snake River dam: Implications for summer flow augmentation

Abstract Rearing subyearling chinook salmon Oncorhynchus tshawytscha (≥60 mm in fork length) were captured in the Snake River and tagged with passive integrated transponders to provide an index of their survival to Lower Granite Dam, the first of eight dams encountered by seaward migrants. Water was released from reservoirs upstream of Lower Granite Dam to augment summer flows and thereby increase subyearling chinook salmon survival. Mean summer flow and maximum summer water temperature in Lower Granite Reservoir were highly correlated (N = 4; r = −0.999). Acknowledging this correlation, we conducted two separate least-squares regressions using detection rate as the dependent variable. Detection rate at Lower Granite Dam was positively related to mean summer flow (N = 4; r 2 = 0.993; P = 0.003) and negatively related to maximum summer water temperature (N = 4; r 2 = 0.984; P = 0.008). Summer flow augmentation increased flow and decreased water temperature in Lower Granite Reservoir especially in low-flow ...

Growth of Wild Subyearling Fall Chinook Salmon in the Snake River

Abstract Growth is an important determinant of life history development for juvenile anadromous salmonids. We collected juvenile fall chinook salmon Oncorhynchus tshawytscha in two reaches of the Snake River to describe growth in fork length (mm/d) and to test for a relation between growth and water temperature. Growth rate during shoreline rearing was significantly higher (P = 0.003) for parr in the warmer of these two reaches (grand means = 1.2 ± 0.04 and 1.0 ± 0.04 mm/d). Because smolts from the two reaches share a common, relatively warm downstream migration route, growth rates were similar between smolts from the two reaches (P = 0.18; grand means = 1.3 ± 0.04 and 1.4 ± 0.04 mm/d). By pooling data across reaches and life stages, we found that growth rate generally increased as water temperature increased (N = 17, r 2 = 0.62, P = 0.0002). The growth rates we observed were probably lower than for fall chinook salmon in a historical rearing area now inaccessible because of dams, but they were still rapi...

Growth and Long-Range Dispersal by Wild Subyearling Spring and Summer Chinook Salmon in the Snake River Basin

Abstract Wild juvenile spring and summer chinook salmon Oncorhynchus tshawytscha typically pass downstream in the Snake River as yearling smolts when migrating seaward. A small number of these fish disperse downstream from natal streams into the Snake River as subyearlings and then continue moving seaward. We estimated that the naturally produced subyearling spring and summer chinook salmon that dispersed into the Snake River in 1993, 1994, and 1997 originated from both wild (67%) and naturalized hatchery (33%) stocks. These fish were large in terms of mean fork length (range, 78–87 mm) during shoreline rearing. While moving seaward, they grew rapidly (range of means, 1.0–1.3 mm/d) to yearling smolt fork lengths (range of means, 122–128 mm). The estimated dispersal distances from natal streams to the first two dams encountered during seaward movement ranged from 172 to 810 km. Although we could not demonstrate seawater entry, we believe that the wild spring and summer chinook salmon had met the growth and...

Forecasting Survival and Passage of Migratory Juvenile Salmonids

Abstract We developed methods to forecast survival and cumulative percent passage for subyearling chinook salmon Oncorhynchus tshawytscha at a dam to help managers effectively time the release of reservoir water to mitigate for passage delays and reduced survival. We tagged Snake River subyearling chinook salmon upstream of a dam from 1993 to 1998 and determined when a subsample of the tagged fish passed the dam. We randomly selected data (1993, 1994, 1996, and 1998) to develop a quadratic discriminant function for predicting which fish would survive to the dam and to develop a multiple-regression equation to predict the date survivors would pass the dam. We used the predicted passage dates within a year to calculate a daily cumulative percent passage forecast and then calculated a 90% forecast interval that varied by year, depending on the number of predicted survivors. We validated the forecast method using data for 1995 and 1997. The 1995 forecasted passage curve differed from the observed passage curv...

Reproduction by the Endangered Cui-ui in the Lower Truckee River

Abstract Adult spawning behavior and emigration of larvae of the endangered cui-ui Chasmistes cujus were studied in a natural side channel of the lower Truckee River. External radio-tags placed on eight apparently did not affect spawning behavior. Cui-uis spawned in clusters of two to seven fish; usually a single female was flanked by two males. Each spawning act lasted 3–6 seconds, and individual fish spawned numerous times. The most active tagged male and female spawned at least 294 times and 114 times, respectively. Individual females broadcast eggs over an area of up to 50 m2. Males spawned over a 4–5-day period, and females over 2.5–4 days. Most spawning occurred at night in water depths ranging from 9 to 43 cm, water velocities ranging from 23 to 87 cm/second, and temperatures of 12–17 C. The preferred spawning substrate was gravel. Peak emergence and out-migration of cui-ui larvae occurred 14 days after peak spawning. Received September 7, 1982 Accepted August 5, 1983

Post-Release Attributes and Survival of Hatchery and Natural Fall Chinook Salmon in the Snake River, Annual Report 1998.

This report summarizes results of research activities conducted primarily in 1997 and 1998. This report communicates significant findings that will aid in the management and recovery of fall chinook salmon in the Columbia River Basin.