Tobias J. Kock

Water Velocity, Turbulence, and Migration Rate of Subyearling Fall Chinook Salmon in the Free-Flowing and Impounded Snake River

Abstract We studied the migratory behavior of subyearling fall Chinook salmon Oncorhynchus tshawytscha in free-flowing and impounded reaches of the Snake River to evaluate the hypothesis that velocity and turbulence are the primary causal mechanisms of downstream migration. The hypothesis states that impoundment reduces velocity and turbulence and alters the migratory behavior of juvenile Chinook salmon as a result of their reduced perception of these cues. At a constant flow (m3/s), both velocity (km/d) and turbulence (the SD of velocity) decreased from riverine to impounded habitat as cross-sectional areas increased. We found evidence for the hypothesis that subyearling Chinook salmon perceive velocity and turbulence cues and respond to these cues by varying their behavior. The percentage of the subyearlings that moved faster than the average current speed decreased as fish made the transition from riverine reaches with high velocities and turbulence to upper reservoir reaches with low velocities and tu...

Diel behavior of rearing fall Chinook salmon

In fisheries science, habitat use is often inferred when fish are sampled or observed in a particular location. Physical habitat is typically measured where fish are found, and thus deemed important to habitat use. Although less common, a more informative approach is to measure or observe fish behavior within given habitats to more thoroughly assess their use of those locations. While this approach better reflects how fish use habitat, fish behavior can be difficult to quantify, particularly at night. For example, Tiffan and others (2002, 2006) were able to quantify habitat availability and characteristics that were important for rearing juvenile fall Chinook Salmon (Oncorhynchus tshawytscha) in the Hanford Reach of the Columbia River.

Downstream Movement of Fall Chinook Salmon Juveniles in the Lower Snake River Reservoirs during Winter and Early Spring

Abstract We conducted a 3-year radiotelemetry study in the lower Snake River to (1) determine whether juvenile fall Chinook salmon Oncorhynchus tshawytscha pass dams during winter, when bypass systems and structures designed to prevent mortality are not operated; (2) determine whether downstream movement rate varies annually, seasonally, and from reservoir to reservoir; and (3) identify some of the factors that contribute to annual, seasonal, and spatial variation in downstream movement rate. Fall Chinook salmon juveniles moved downstream up to 169 km and at a sufficiently fast rate (7.5 km/d) such that large percentages (up to 93%) of the fish passed one or more dams during the winter. Mean downstream movement rate varied annually (9.2–11.3 km/d), increased from winter (7.5 km/d) to spring (16.4 km/d), and increased (from 6.9 to 16.8 km/d) as fish moved downstream from reservoir to reservoir. Fish condition factor at tagging explained some of the annual variation in downstream movement rate, whereas wate...

Evaluation of Strobe Lights to Reduce Turbine Entrainment of Juvenile Steelhead (Oncorhynchus mykiss) at Cowlitz Falls Dam, Washington

Abstract We conducted a radiotelemetry evaluation to determine if strobe lights could be used to decrease turbine entrainment of juvenile steelhead (Oncorhynchus mykiss) at Cowlitz Falls Dam, Washington. We found that radio-tagged juvenile steelhead approached and entered two spillbays (one lighted, one unlighted) in equal proportions. However, the presence of strobe lights was associated with decreased spillbay residence time of juvenile steelhead and increased passage through induction slots (secondary turbine intakes located upstream of the ogee on the spillway). Mean residence time of tagged fish inside the lighted spillbay was 14 min compared to 62 min inside the unlighted spillbay. Radio-tagged steelhead passed through induction slots at a higher proportion in the lighted spillbay (55%) than in the unlighted spillbay (26%). Recent studies have suggested that strobe lights can induce torpor in juvenile salmonids. We believe that strobe light exposure affected fish in our study at a location where they were susceptible to high flows thereby reducing mean residence time and increasing the proportion of tagged fish entering induction slots in the lighted spillbay. Our results suggest that factors such as deployment location, exposure, and flow are important variables that should be considered when evaluating strobe lights as a potential fish-deterring management tool.

Passage survival of juvenile steelhead, coho salmon, and Chinook salmon in Lake Scanewa and at Cowlitz Falls Dam, Cowlitz River, Washington, 2010–16

....................................................................................................................................................................1 Chapter A. Reservoir Passage Survival of Juvenile Steelhead, Coho Salmon, and Chinook Salmon in Lake Scanewa, Upper Cowlitz River, Washington, 2010, 2011, and 2016 ..................................................................2 Introduction ............................................................................................................................................................2 Methods .................................................................................................................................................................4 Fish Tagging and Release .................................................................................................................................4 Monitoring Array.................................................................................................................................................5 Data Analysis .....................................................................................................................................................5 Results ...................................................................................................................................................................7 Fish Tagging and Release .................................................................................................................................7 River Conditions............................................................................................................................................... 10 Downstream Movement ................................................................................................................................... 10 Reservoir Passage Survival ............................................................................................................................. 15 Discussion ............................................................................................................................................................ 17 References Cited .................................................................................................................................................. 18 Chapter B. Dam Passage Survival of Juvenile Steelhead, Coho Salmon, and Chinook Salmon at Cowlitz Falls Dam, Cowlitz River, Washington, 2013-16 ...................................................................................................... 2

Preliminary evaluation of the behavior and movements of adult spring Chinook salmon in the Chehalis River, southwestern Washington, 2014

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BEHAVIOR AND MOVEMENT OF FORMERLY LANDLOCKED JUVENILE COHO SALMON AFTER RELEASE INTO THE FREE- FLOWING COWLITZ RIVER, WASHINGTON

Abstract Formerly landlocked Coho Salmon (Oncorhynchus kisutch) juveniles (age 2) were monitored following release into the free-flowing Cowlitz River to determine if they remained in the river or resumed seaward migration. Juvenile Coho Salmon were tagged with a radio transmitter (30 fish) or Floy tag (1050 fish) and their behavior was monitored in the lower Cowlitz River. We found that 97% of the radio-tagged fish remained in the Cowlitz River beyond the juvenile outmigration period, and the number of fish dispersing downstream decreased with increasing distance from the release site. None of the tagged fish returned as spawning adults in the 2 y following release. We suspect that fish in our study failed to migrate because they exceeded a threshold in size, age, or physiological status. Tagged fish in our study primarily remained in the Cowlitz River, thus it is possible that these fish presented challenges to juvenile salmon migrating through the system either directly by predation or indirectly by competition for food or habitat. Given these findings, returning formerly landlocked Coho Salmon juveniles to the free-flowing river apparently provided no benefit to the anadromous population. These findings have management implications in locations where landlocked salmon have the potential to interact with anadromous species of concern.

Quantifying the Behavioral Response of Spawning Chum Salmon to Elevated Discharges from Bonneville Dam, Columbia River : Annual Report 2005-2006.

In unimpounded rivers, Pacific salmon (Oncorhynchus spp.) typically spawn under relatively stable stream flows, with exceptions occurring during periodic precipitation events. In contrast, hydroelectric development has often resulted in an artificial hydrograph characterized by rapid changes in discharge and tailwater elevation that occur on a daily, or even an hourly basis, due to power generation (Cushman 1985; Moog 1993). Consequently, populations of Pacific salmon that are known to spawn in main-stem habitats below hydroelectric dams face the risks of changing habitat suitability, potential redd dewatering, and uncertain spawning success (Hamilton and Buell 1976; Chapman et al. 1986; Dauble et al. 1999; Garland et al. 2003; Connor and Pflug 2004; McMichael et al. 2005). Although the direct effects of a variable hydrograph, such as redd dewatering are apparent, specific effects on spawning behavior remain largely unexplored. Chum salmon (O. keta) that spawn below Bonneville Dam on the Columbia River are particularly vulnerable to the effects of water level fluctuations. Although chum salmon generally spawn in smaller tributaries (Johnson et al. 1997), many fish spawn in main-stem habitats below Bonneville Dam near Ives Island (Tomaro et al. 2007; Figure 1). The primary spawning area near Ives Island is shallow and sensitive to changes in water level caused by hydroelectric power generation at Bonneville Dam. In the past, fluctuating water levels have dewatered redds and changed the amount of available spawning habitat (Garland et al. 2003). To minimize these effects, fishery managers attempt to maintain a stable tailwater elevation at Bonneville Dam of 3.5 m (above mean sea level) during spawning, which ensures adequate water is provided to the primary chum salmon spawning area below the mouth of Hamilton Creek (Figure 1). Given the uncertainty of winter precipitation and water supply, this strategy has been effective at restricting spawning to a specific riverbed elevation and providing minimum spawning flows that have the greatest chance of being maintained through egg incubation and fry emergence. However, managing the lower Columbia River for a stable tailwater elevation does not provide much operational flexibility at Bonneville Dam, which has little storage capacity. When river discharges increase due to rain events, the traditional approach has been to pass excess water at night to maintain stable tailwater elevations during the daytime. The underlying assumption of this strategy, referred to as reverse load following, is that fish do not spawn at night. However, Tiffan et al. (2005) showed that this assumption is false by documenting nighttime spawning by chum salmon in the Ives Island area. Similarly, McMichael et al. (2005) reported nighttime spawning by Chinook salmon (O. tshawytscha) in the Columbia River, indicating that diel spawning may be a common occurrence in Pacific salmon. During the latter portion of the chum spawning period in December 2003 and 2004, discharges from Bonneville Dam increased from an average of 3,398 m3/s (tailwater elevation {approx} 3.5 m above mean sea level) during the day to over 5,664 m3/s (tailwater elevation {approx} 5.1 m) at night, with peak discharges of 7,080 m{sup 3}/s (tailwater elevation {approx} 6.1 m). This caused concern among fishery managers regarding the potential effects of these high discharges on this population of spawning chum salmon, which is listed under the Endangered Species Act (National Oceanic and Atmospheric Administration 1999). We hypothesized that increased water velocities associated with elevated tailwaters might alter chum salmon spawning behavior if water velocities at redd locations increased beyond the range of suitability (>0.8 m/s; Salo 1991). In 2005, we investigated the movement and behavioral responses of spawning chum salmon at Ives Island to increased tailwater elevations at Bonneville Dam. We used acoustic telemetry to determine if the higher velocities associated with increased tailwater elevations caused fish to leave their redds. We related the duration fish were away from redds and the distances moved to water velocities estimated from a two-dimensional hydrodynamic model. Finally, we described specific changes in spawning behavior (e.g., nest digging; swimming activity) during elevated-tailwater tests using a dual-frequency identification sonar (DIDSON).