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Tobias J. Kock

Publications and source records attributed to Tobias J. Kock.

At least 73 records · Page 4Linked to original sources
USGS2014

Evaluation of the behavior and movement of adult summer steelhead in the lower Cowlitz River, Washington, following collection and release, 2013-2014

Summer steelhead ( Oncorhynchus mykiss ) produced by a hatchery on the lower Cowlitz River, Washington, support a popular sport fishery during June–September each year. Many of these fish return to the Cowlitz Salmon Hatchery and are held until they are spawned in December. In the past, fishery managers have released some of the steelhead that return to the hatchery at downstream release sites (hereafter referred to as “recycled steelhead”) to increase angling opportunity. The recycling of summer steelhead is a potential use of hatchery fish that can benefit anglers in the lower Cowlitz River, provided these fish are harvested or return to the hatchery. However, recycled steelhead that are not removed from the river could compete against or spawn with wild winter steelhead, which would be a negative consequence of recycling. The Washington Department of Fish and Wildlife (WDFW) conducted an evaluation during 1998 and recycled 632 summer steelhead. They determined that 55 percent of the recycled steelhead returned to the hatchery and 15 percent of the fish were harvested by anglers. The remaining 30 percent of recycled fish were not known to have been removed from the river. Recycling has not occurred in recent years because definitive studies have not been conducted to determine the fate of the fish that remain in the lower Cowlitz River after being recycled. The U.S. Geological Survey and WDFW conducted a 2-year study during 2012–2014 to quantify recycled steelhead that (1) returned to the hatchery, (2) were captured by anglers, or (3) remained in the river. All recycled steelhead were marked with a Floy ® tag and opercle punch, and 20 percent of the recycled fish were radio-tagged to determine post-release behavior and movement patterns, and to describe locations of tagged fish that remained in the river during the spawning period. During 2012–2013, we recycled 549 steelhead and determined that 50 percent of the fish returned to the hatchery, 18 percent of the fish were harvested by anglers, and 32 percent of the fish were not known to have been removed from the river. During October–December 2012, only 9 percent of the radio-tagged steelhead remained in the lower Cowlitz River and none of these fish entered tributaries monitored by fixed-telemetry sites. The second year of the evaluation was conducted during 2013–2014. A total of 502 steelhead were recycled during June–August and releases were conducted weekly with group sizes that ranged from 30 to 76 fish. Results from 2013–2014 were similar to results from 2012–2013. Fifty percent (251 fish) of the recycled steelhead returned to the hatchery, 20 percent (100 fish) were harvested by anglers, and 30 percent (151 fish) were unaccounted for. The median elapsed time from release to hatchery return was 13 days, and the median elapsed time from release to capture by an angler was 11 days. The percentage of unaccounted-for steelhead in the general population was moderately high (30 percent), but detection records of radio-tagged fish suggest that few recycled steelhead were present in the lower Cowlitz River during the spawning period. A total of 109 steelhead were radio-tagged during 2013–2014, and most of these fish (88 percent) moved upstream following release and entered the Trout Hatchery–Salmon Hatchery reach (river miles 44–51). The median elapsed time from release to reach entry was 4.6 days (range of 0.5–65.5 days). After fish entered this reach, they spent a considerable amount of time near the Cowlitz Trout Hatchery (median residence time of 16.7 hours) or Cowlitz Salmon Hatchery (median residence time of 146.3 hours), or they moved back and forth between these two sites. Thirty radio-tagged steelhead made at least two trips between the sites and some fish made as many as seven trips. Detection records showed that 61 percent (66 fish) of the radio-tagged fish returned to the hatchery reach and 21 percent (23 fish) of the fish were captured by anglers. The remaining 18 percent (20 fish) of the radio-tagged fish had various fates. One fish (less than 1 percent) left the Cowlitz River and nine fish (8 percent) died, were harvested, or spit their transmitter near boat launches in the river. The remaining 10 fish (9 percent) had the potential to interact with winter steelhead. Four tagged steelhead (4 percent) entered lower Cowlitz River tributaries (two fish in the Toutle River; two fish in Salmon Creek) during October and November, and five tagged fish (5 percent) were last detected in the lower Cowlitz River in October. One fish (less than 1 percent) was never detected after being released. We measured the diameter of opercle punches in recycled steelhead to determine the temporal effectiveness of these marks. A total of 116 opercle punches were measured—36 were measured at the time of tagging and 80 were measured when fish returned to the hatchery. Opercle punches remained open for less than 1 month. None of the fish that returned to the hatchery more than 30 days after release had opercle punches that were open. All recycled steelhead were marked with a Floy ® tag and opercle punch. However, if a steelhead lost its Floy ® tag and was captured by an angler, or returned to the hatchery more than 30 days after being recycled, it likely would not have been accurately identified as having been recycled because of regrowth of the opercle punch. During 2013–2014, at least 70 percent of the recycled steelhead were removed from the lower Cowlitz River by anglers, returned to the hatchery, or left the river. Radiotelemetry data indicated that a maximum of 9 percent of the radio-tagged fish remained in the lower Cowlitz River during the spawning period and only 4 percent of the radio-tagged fish entered tributaries where wild steelhead are known to spawn. These results are consistent with findings from previous studies. Overall, results from these studies suggest that about one-third of the recycled steelhead were not known to have been removed from the river. However, the radiotelemetry data indicated that only about 10 percent of the recycled steelhead were present in the lower Cowlitz River during late autumn and early winter, and few of those fish (0 in 2012–2013 and 4 in 2013–2014) entered tributaries where winter steelhead spawn. These results have management implications in the lower Cowlitz River where the risks and rewards of steelhead recycling will be weighed to determine the future of the recycling program.

Washinton↗
USGS2013

Behavior and movement of adult summer steelhead following collection and release, lower Cowlitz River, Washington, 2012--2013

Executive Summary Historically, adult summer steelhead Oncorhynchus mykiss returning to hatcheries on the lower Cowlitz River were sometimes transported and released in the river (recycled) to provide additional angling opportunity for the popular sport fishery in the basin. However, this practice has not been used in recent years because of concerns associated with interactions between hatchery fish and wild fish. Fishery managers were interested in resuming recycling but lacked information regarding effects of this practice on wild steelhead so we conducted a study during 2012–2013 to: (1) enumerate recycled steelhead that returned to the hatchery or were removed by anglers; and (2) determine if steelhead that were not removed from the river remained in the system where they could interact with wild fish. During June–August 2012, a total of 549 summer steelhead were captured at the Cowlitz Salmon Hatchery, tagged, and released downstream near the Interstate 5 Bridge. All recycled steelhead were tagged with a white Floy ® tag and opercle-punched; 109 (20 percent) of these fish also were radio-tagged. All adult steelhead that return to the hatchery were handled by hatchery staff so recycled steelhead that returned to the hatchery were enumerated daily. A creel survey and voluntary angler reports were used to determine the number of recycled steelhead that were caught by anglers. We established three fixed telemetry monitoring sites on the mainstem Cowlitz River and eight additional sites were deployed on tributaries to the lower Cowlitz River where wild winter steelhead are known to spawn. We also conducted mobile tracking from a boat during October 2012, November 2012, and January 2013 to locate radio-tagged fish. A total of 10,722 summer steelhead were captured at the Cowlitz Salmon Hatchery in 2012, which was the largest return since 2008. River flows during much of the study period were similar to 2008–2011 average flows, however, high-flow periods in July and November 2012 were nearly twice as high as the 2008–2011 average flows. We determined that 50 percent (273 fish) of the recycled steelhead returned to the hatchery and 18 percent (102 fish) of the recycled steelhead were caught by anglers. Most (243 fish; 89 percent) of the recycled steelhead that returned to the hatchery were recollected during July–August. The average elapsed time from release to recapture at the hatchery was 9 days (d) and 72 percent (182 fish) of the fish returned to the hatchery within 14 d of release. These trends were similar for recycled steelhead that were caught by anglers. Most fish were caught during July–August and the median time from release to capture was 10 d. We determined that 65 percent (70 fish) of the angler-caught fish returned to the hatchery within 14 d of release. River flows appeared to affect both hatchery returns and angler catch. The daily number of recycled steelhead that were recollected at the hatchery were low during periods when river flows were decreasing and high during periods when river flows were increasing. Conversely, daily angler catch of recycled steelhead generally was low when flows were increasing and high when flows were decreasing. We determined that 32 percent of the recycled steelhead (174 fish) were not removed from the lower Cowlitz River, based on observations from hatchery returns and angler reports, but results from the radio-tagged fish were insightful for understanding what may have happened to these fish. By comparison, we determined that 24 percent of the radio-tagged fish were not known to have been removed from the river. We determined that 12 percent of these fish were actively moving in the lower Cowlitz River during October 2012–January 2013. None of the radio-tagged fish were detected in tributaries during the study period except for a single fish that spent approximately 7 d in the Toutle River during early September. During October 2012–January 2013, 10 percent of the radio-tags from recycled steelhead were detected near popular fishing areas, and 2 percent of the radio-tagged steelhead were never detected during the study period. We suspect that a large proportion of these fish may have been harvested and not reported, or died. Detection patterns of radio-tagged steelhead showed that most fish (82 percent) moved upstream from the release site and were detected at the Trout Hatchery and the Barrier Dam sites. The median time from release to detection at these sites was 3.7 d and many of these fish made multiple trips between the two sites. Nearly one-third (29 percent) of the recycled steelhead that were detected at the Trout Hatchery and the Barrier Dam made at least two trips between the sites and some fish made as many as six trips. Radio-tagged fish that remained in the lower Cowlitz River during the spawning period (December 2012–January 2013) were observed in the river reach between the mouth of Ostrander Creek (river mile 10) and the Trout Hatchery (river mile 44). During this study, we collected data on opercle punch regrowth rates to understand the temporal effectiveness of this marking technique. We took opercle measurements for a total of 190 fish during the study. Fresh opercle punches were measured for 63 fish at the time of marking, and the remaining 127 fish were measured when fish returned to the hatchery. We determined that opercle punches remained open for about 30 d. The holes appeared to regrow slowly in the first 20 d after marking, but regrowth accelerated during the 20–30 d post-marking period. After 30 d, all opercle punches that we observed had completely closed due to tissue regrowth. Our study showed that a large proportion (68 percent) of the recycled steelhead were removed from the lower Cowlitz River. These fish primarily entered the hatchery or were caught by anglers within 14 d of release, which suggests that they present minimal risk to wild fish in the system. However, the remaining fish (32 percent) could not be accounted for, which may complicate fisheries management decisions associated with recycling summer steelhead. Findings from the radiotelemetry study suggest that unreported harvest or mortality could explain a large proportion of those fish that were not reported as having been removed from the river. Furthermore, intensive monitoring of the key spawning tributaries failed to detect a single fish during the spawning period. These findings were supported by observations from weir traps operated by the Washington Department of Fish and Wildlife. Our findings indicate that additional research may be warranted to further examine the effects of recycling hatchery summer steelhead in the lower Cowlitz River.

Washington↗
USGS2013

Review of a model to assess stranding of juvenile salmon by ship wakes along the Lower Columbia River, Oregon and Washington

Long period wake waves from deep draft vessels have been shown to strand small fish, particularly juvenile Chinook salmon Oncorhynchus tschawytcha, in the lower Columbia River (LCR). The U.S. Army Corps of Engineers is responsible for maintaining the shipping channel in the LCR and recently conducted dredging operations to deepen the shipping channel from an authorized depth of 40 feet(ft) to an authorized depth of 43 ft (in areas where rapid shoaling was expected, dredging operations were used to increase the channel depth to 48 ft). A model was developed to estimate stranding probabilities for juvenile salmon under the 40- and 43-ft channel scenarios, to determine if channel deepening was going to affect wake stranding (Assessment of potential stranding of juvenile salmon by ship wakes along the Lower Columbia River under scenarios of ship traffic and channel depth: Report prepared for the Portland District U.S. Army Corps of Engineers, Portland, Oregon). The U.S. Army Corps of Engineers funded the U.S. Geological Survey to review this model. A total of 30 review questions were provided to guide the review process, and these questions are addressed in this report. In general, we determined that the analyses by Pearson (2011) were appropriate given the data available. We did identify two areas where additional information could have been provided: (1) a more thorough description of model diagnostics and model selection would have been useful for the reader to better understand the model framework; and (2) model uncertainty should have been explicitly described and reported in the document. Stranding probability estimates between the 40- and 43-ft channel depths were minimally different under most of the scenarios that were examined by Pearson (2011), and a discussion of the effects of uncertainty given these minimal differences would have been useful. Ultimately, however, a stochastic (or simulation) model would provide the best opportunity to illustrate uncertainty within a given set of model predictions, but such an approach would require a substantial amount of additional data collection. Several review questions focused on the accuracy and precision of the model estimates, but we were unable to address these questions because of the limited data that currently exists regarding wake stranding in the LCR. Additional field studies will be required to validate findings from Pearson (2011), if concerns regarding accuracy and precision remain a priority. Although the Pearson (2011) model provided a useful examination of stranding under pre-construction and post-construction conditions, future research will be required to better understand the effects of wake stranding on juvenile salmonids throughout the entire LCR. If additional information on wake stranding is desired in the future, the following topics may be of interest: (1) spatial examination of wake stranding throughout the entire LCR; (2) additional evaluation of juvenile salmonid behavior and population dynamics; (3) assessing and integrating predicted changes in ship development; and (4) assessing and integrating predicted changes in climate on environmental factors known to cause stranding.

Oregon;Washington↗
USGS2013

Evaluation of the behavior and movement patterns of adult coho salmon and steelhead in the North Fork Toutle River, Washington, 2005-2009

The 1980 eruption of Mount St. Helens severely affected the North Fork Toutle River (hereafter Toutle River), Washington, and threatened anadromous salmon (Oncorhynchus spp.) populations in the basin. The Toutle River was further affected in 1989 when a sediment retention structure (SRS) was constructed to trap sediments in the upper basin. The SRS completely blocked upstream volitional passage, so a fish collection facility (FCF) was constructed to trap adult coho salmon (O. kisutch) and steelhead (O. mykiss) so they could be transported upstream of the SRS. The Washington Department of Fish and Wildlife (WDFW) has operated a trap-and-haul program since 1989 to transport coho salmon and steelhead into tributaries of the Toutle River, upstream of the SRS. Although this program has allowed wild coho salmon and steelhead populations to persist in the Toutle River basin, the trap-andhaul program has faced many challenges that may be limiting the effectiveness of the program. We conducted a multi-year evaluation during 2005–2009 to monitor tagged fish in the upper Toutle River to provide information on the movements and behavior of adult coho salmon and steelhead, and to evaluate the efficacy of the FCF. Radio-tagged coho salmon and steelhead were released: (1) in Toutle River tributaries to evaluate the behavior and movements of fish released as part of the trap-and-haul program; (2) between the FCF and SRS to determine if volitional upstream passage through the SRS spillway was possible; (3) in the sediment plain upstream of the SRS to determine if volitional passage through the sediment plain was possible; and (4) downstream of the FCF to evaluate the efficacy of the structure. We also deployed an acoustic camera in the FCF to monitor fish movements near the entrance to the FCF, and in the fish holding vault where coho salmon and steelhead are trapped. A total of 20 radio-tagged coho salmon and 10 radio-tagged steelhead were released into Alder and Hoffstadt Creeks, the locations where trap-and-haul fish were released during 2005–2006. None of the tagged fish left the tributaries where they were released, but four radio tags were detected near the release sites, and it was not possible to determine if this was because the transmitters were regurgitated, or if some of the tagged fish had died. The results from this portion of the study indicated that trap-and-haul fish remain in the tributaries where they can spawn, but the trap-and-haul process is labor-intensive, and handling stress and mortality could occur. Tagged-fish releases upstream of the FCF showed that the SRS spillway was a complete migration barrier for all coho salmon and most steelhead. We released a total of 20 radio-tagged coho salmon and 23 radio-tagged steelhead during 2005–2007. No tagged coho salmon passed upstream through the SRS spillway, whereas 13 percent of the radio-tagged steelhead did migrate upstream through the structure. Radio-tagged coho salmon and steelhead that did not pass upstream remained in the FCF–SRS reach for an average of 7.5 and 16.1 d, respectively, before moving downstream. These data show that trap-and-haul releases of fish immediately upstream of the FCF would not be beneficial to coho salmon and steelhead populations in the system. Releasing tagged fish into the sediment plain was only moderately successful for coho salmon, but a large percentage of tagged steelhead moved upstream through the sediment plain to areas where spawning could presumably occur. During 2005–2009, we released 47 tagged coho salmon and 65 tagged steelhead into the sediment plain. Only 28 percent of the coho salmon were later detected upstream of the sediment plain, and the highest percentage of the release group (62 percent) never left the sediment plain. However, 69 percent of the steelhead moved upstream through the sediment plain and entered Toutle River tributaries or remained in the mainstem Toutle River where spawning could presumably occur. Adult steelhead can survive freshwater spawning, outmigrate to the ocean, and then return to spawn in successive years; 12 percent of the tagged steelhead successfully moved downstream of the FCF after the spawning period, and 5 percent of the tagged steelhead returned to the FCF a year after they were originally tagged. Evaluations at the FCF showed that the structure was not efficient at collecting adult salmon. During 2008–2009, 9 radio-tagged coho salmon and 11 radio-tagged steelhead were released to observe behavior near the facility and to estimate the recapture rate in the FCF. None of the tagged coho salmon were recaptured and only 27 percent of the tagged steelhead were recaptured. Additionally, we observed fish behavior at the FCF with an acoustic camera and found that relatively large numbers (>100 fish/sampling period) of adult salmon entered the FCF but similar numbers of fish exited during these periods as well. This suggested that the efficacy of the FCF was low. Our study was limited by the number of fish that could be handled each year and the number of transmitters that could be purchased annually, but our evaluations provided the first empirical data on adult salmon behavior and movement patterns in the Toutle River since the 1980 eruption of Mount St. Helens. Since the completion of this work, the U.S. Army Corps of Engineers has altered the SRS spillway and sediment plain; however, our results do provide information to assist fishery managers tasked with the complex management of wild salmon populations in the Toutle River. Future evaluations of juvenile and adult salmon behavior and movement likely will be required to effectively manage these populations in this complex system.

Washington↗
USGS2013

Snake River fall Chinook salmon life history investigations: Annual report 2011 (April 2011 - March 2012)

Executive Summary Chapter One &ndash; This chapter was published in the Transactions of the American Fisheries Society in 2012. We conducted a three-year radiotelemetry study in the lower Snake River to answer the questions: do fall Chinook salmon juveniles pass dams during winter when bypass systems and structures designed to prevent mortality are not operated; does downstream movement rate vary annually, seasonally, and from reservoir to reservoir; and, what are 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 fast enough (7.5 km/d) such that large percentages (up to 93%) of the fish passed one or more dams during 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 (6.9-16.8 km/d) as fish moved downstream from reservoir to reservoir. Fish condition factor at tagging explained some of the annual variation ( P &le; 0.01) in downstream movement rate, whereas water particle velocity ( P &le;0.0001) and temperature ( P &le;0.0001) explained portions of the seasonal variation. An increase in migrational disposition as fish moved downstream helped explain the spatial variation ( P =0.05-0.07). The potential cost of winter movement might be reduced survival due to turbine passage when the bypass systems and spillway passage structures are not operated. Efforts to understand and increase passage survival of winter migrants in large impoundments might help to rehabilitate some imperiled anadromous salmonid populations. Chapter Two &ndash; Natural juvenile fall Chinook salmon in the Snake and Clearwater rivers exhibit two life history strategies. &ldquo;Ocean-type&rdquo; fish migrate out to the ocean in their first summer of life as subyearlings, but &ldquo;reservoir-type&rdquo; fish delay seaward migration during the summer, and some overwinter in reservoirs before continuing their migration the following spring as yearlings. Earlier emerging fish produced in the Snake River tend to adopt the ocean-type life history whereas many of the later emerging fish from the Clearwater River tend to adopt the reservoirtype life history. The underlying cause of the reservoir-type life history is poorly understood, but we believe there may be link to physiological development. We used traditional markers of the parr-smolt transformation (smoltification), including gill Na + /K + -ATPase activity and thyroid hormone levels, along with gene expression microarrays to assess the development of ocean-type juvenile fall Chinook salmon and then compared it to that of juvenile fall Chinook salmon from the Clearwater River. We showed that parr in the Snake River are physiologically distinct from actively-migrating smolts but smolts migrating early and late in the summer and fall are physiologically similar. Juvenile fall Chinook salmon collected from the Clearwater River were similar in size to early-migrating smolts in the Snake River but were most physiologically similar to Snake River parr. Genes differentially expressed between Snake River parr and smolts and between fish from the Clearwater River and smolts from the Snake River were involved in the cell cycle, steroid metabolism and other metabolic pathways, and DNA repair and packaging. Many of the genes differentially expressed in these comparisons had expression patterns that correlated with gill Na + /K + -ATPase activity, suggesting that they were related to smoltification and migration status. Chapter Three &ndash; Natural subyearlings produced in the Clearwater River are exposed to cool (~10-12&deg;C) temperatures when water is released from Dworshak Reservoir for summer flow augmentation. Total dissolved gas (TDG) levels range from 100-110% in the lower Clearwater iv River. When fish move into the Snake River, they encounter temperatures up to 24&deg;C at the surface which have the potential to incur gas bubble disease (GBD) in fish as dissolved gases in their bodies expand under warmer temperatures. This may result in both direct and indirect mortality, but this situation has been little studied. We conducted laboratory experiments to examine subyearling mortality rates and incidence and severity of GBD in fish that were moved between waters that varied in TDG and temperature. Fish experienced significant mortality only at temperatures of 25&deg;C, which increased with exposure time. However there was no significance difference in mortality between fish acclimated to 100% TDG and 110% TDG. Fish that died did show signs of GBD. Generally, signs of GBD such as bubbles in the lateral line and unpaired fins were higher in fish acclimated at 110% TDG than in fish acclimated at 100% TDG, but there were few trends related to exposure temperature. Field measurements of TDG showed that TDG ranged from about 100% to 122.5% at some locations. Generally, TDG fluctuated daily, up to 8% during August and early September, and was highest late in the afternoon and lowest in the early morning. Laboratory results and field monitoring demonstrated that emigrating juvenile salmon can potentially be at risk from elevated temperatures, TDG, and GBD albeit to an unknown extent, which may increase their vulnerability to predation. Chapter Four &ndash; We conducted monthly beam trawling in Lower Granite and Little Goose reservoirs to describe the seasonal abundance of benthic epifauna that are potentially important as prey to juvenile fall Chinook salmon. The predominant taxa collected were Siberian prawns, the opossum shrimp Neomysis mercedis , and the amphipod Corophium sp. Prawns were relatively abundant at shallow sites in both reservoirs in June, but were more abundant at deep sites in lower and middle reservoir reaches in autumn. Prawn densities were commonly <0.2/m2. Prawn length-frequency data indicated that there were at least two size classes. Juvenile prawns present in shallow water more often than adult prawns, which were generally only found in deep water by autumn. Ovigerous prawns had an average of 171 eggs, which represented about 11.5% of their body weight. Limited diet analyses suggested that prawns consumed Corophium , Neomysis , and aquatic insects. Neomysis dominated all catches both in terms of abundance and biomass, and they were more abundant in Lower Granite compared to Little Goose reservoir. Neomysis were more abundant at shallow sites than at deep sites. Corophium were present in our collections but were never abundant, probably because our trawl was not effective at capturing them. The caloric content of prawns (4,782 Kcal), Neomysis (4,962 Kcal), and Corophium (4,926 Kcal) indicates that these prey would be energetically profitable for juvenile salmon. Subyearling fall Chinook salmon prey heavily on Neomysis and Corophium at times, but the importance of prawns as prey is uncertain.

Oregon, Washington↗
USGS2012

Elevated streamflows increase dam passage by juvenile coho salmon during winter: Implications of climate change in the Pacific Northwest

A 4-year evaluation was conducted to determine the proportion of juvenile coho salmon Oncorhynchus kisutch passing Cowlitz Falls Dam, on the Cowlitz River, Washington, during winter. River and reservoir populations of coho salmon parr were monitored using radiotelemetry to determine if streamflow increases resulted in increased downstream movement and dam passage. This was of interest because fish that pass downstream of Cowlitz Falls Dam become landlocked in Riffe Lake and are lost to the anadromous population. Higher proportions of reservoir-released fish (0.391-0.480) passed Cowlitz Falls Dam than did river-released fish (0.037-0.119). Event-time analyses demonstrated that streamflow increases were important predictors of dam passage rates during the study. The estimated effect of increasing streamflows on the risk of dam passage varied annually and ranged from 9% to 75% for every 28.3 m 3 /s increase in streamflow. These results have current management implications because they demonstrate the significance of dam passage by juvenile coho salmon during winter months when juvenile fish collection facilities are typically not operating. The results also have future management implications because climate change predictions suggest that peak streamflow timing for many watersheds in the Pacific Northwest will shift from late spring and early summer to winter. Increased occurrence of intense winter flood events is also expected. Our results demonstrate that juvenile coho salmon respond readily to streamflow increases and initiate downstream movements during winter months, which could result in increased passage at dams during these periods if climate change predictions are realized in the coming decades.

Washington↗
USGS2012

Downstream movement of fall Chinook salmon juveniles in the lower Snake River reservoirs during winter and early spring

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 water particle velocity and temperature explained portions of the seasonal variation. An increase in migrational disposition as fish moved downstream helped to explain the spatial variation. The potential cost of winter movement might be reduced survival due to turbine passage at a time when the bypass systems and spillway passage structures are not operated. Efforts to understand and increase passage survival of winter migrants in large impoundments might help to rehabilitate some imperiled anadromous salmonid populations.

Snake River↗
USGS2012

Behavior and passage of juvenile salmonids during the evaluation of a behavioral guidance structure at Cowlitz Falls Dam, Washington, 2011

Executive Summary A radiotelemetry evaluation was conducted during April&ndash;October 2011 to describe movement patterns, forebay behavior, and passage of juvenile steelhead, coho salmon, and Chinook salmon at Cowlitz Falls Dam, Washington. The primary focus of the study was to describe fish behavior near a behavioral guidance structure (BGS) and floating surface collector (FSC) deployed upstream of Cowlitz Falls Dam. A secondary focus was to determine the proportion of tagged fish that were detected near spillbays 2 and 3 on the dam, because this location has been proposed for deploying weir boxes as an additional dam-based collection alternative in the future. Juvenile steelhead ( Oncorhynchus mykiss ), coho salmon ( Oncorhynchus kisutch ), and Chinook salmon ( Oncorhynchus tshawytscha ) were collected and tagged at the Cowlitz Falls Fish Collection Facility and transported upstream where they were released into the Cowlitz and Cispus Rivers. We radio-tagged and released 110 juvenile steelhead, 110 juvenile coho salmon, and 110 juvenile Chinook salmon and monitored their movements in and around the BGS/FSC complex, at the dam, and downstream of the dam. We used detection records and a Markov chain model to calculate probabilities of movement between specific areas in the forebay of Cowlitz Falls Dam. These areas are referred to as states and the Markov chain model was used to create a series of tables, called transition matrices, that contained estimated probabilities of movement between states. These probabilities were insightful for understanding how radio-tagged fish moved near the BGS, FSC, and spillbays. Most tagged fish (89&ndash;91 percent) moved downstream of release sites (9 or 22 rkm upstream of the dam) and were detected in the dam forebay during the study period. Tagged fish that encountered the BGS on their first approach to the dam were distributed across the forebay, which supports the concept of using a BGS to concentrate fish near a collector entrance in the dam forebay. We found that 14 percent of the steelhead, 18 percent of the coho salmon, and 17 percent of the Chinook salmon encountered the FSC discovery area without BGS guidance on their first trip through the forebay. The BGS guided 36 percent of the steelhead, 22 percent of the coho salmon, and 46 percent of the Chinook salmon to the FSC discovery area when fish first entered the forebay, which resulted in 40&ndash;63 percent (by species) of the tagged fish arriving at the FSC discovery area. Movement patterns along the BGS showed that fish were likely to guide along the device, but also demonstrated the tendency of fish to move under the BGS and downstream to Cowlitz Falls Dam. Differential distribution among sucker species within the Williamson River Delta and between the delta and adjacent lakes indicated that shortnose suckers likely benefited more from the restored Williamson River Delta than Lost River or Klamath largescale suckers ( Catostomus snyderi ). Catch rates in shallow-water habitats within the delta were higher for shortnose and Klamath largescale sucker larvae than for larval Lost River suckers in 2008, 2009, and 2010. Shortnose suckers also comprised the greatest portion of age-0 suckers captured in the Williamson River Delta in all 3 years of the study. The relative abundance of age-1 shortnose suckers was high in our catches compared to age-1 Lost River suckers in 2009 and 2010. Tagged fish that arrived at Cowlitz Falls Dam were distributed across the dam face but a high percentage of each species (65 percent of steelhead; 61 percent of coho salmon; 71 percent of Chinook salmon) arrived on the northern side of the dam. Movement probabilities near spillbays 1 and 4 showed a strong preference for tagged fish to move from the outer edges of the dam towards the center of the dam where they were detected at the debris barrier (range of probabilities = 0.690&ndash;0.841). We found that 76 percent of the steelhead, 61 percent of the coho salmon, and 92 percent of the Chinook salmon were detected at spillbays 2 or 3 during the study. This behavior supports the strategy of weir box deployments in spillbays 2 and 3 for future dam-based collection options. Tagged fish that arrived at the dam commonly moved upstream and were detected at the BGS or FSC discovery area. This behavior provided a secondary opportunity for fish to encounter the FSC discovery area and we found that in total, 72 percent of the steelhead, 48 percent of the coho salmon, and 92 percent of the Chinook salmon were detected near the FSC while residing in the forebay. Overall, 88 percent of the steelhead, 76 percent of the coho salmon, and 95 percent of the Chinook salmon that entered the forebay were detected near the FSC or in spillbays 2 and 3. Turbine passage was the most common passage route for tagged fish at Cowlitz Falls Dam during 2011. We found that 40 percent of the steelhead, 52 percent of the coho salmon, and 33 percent of the Chinook salmon passed through turbines. An additional 22 percent of the steelhead and 32 percent of the coho salmon passed through turbines or spillways when both passage routes were available. Fish collection numbers were relatively low during 2011 compared to long-term averages. In total, 37 percent of the steelhead, 14 percent of the coho salmon, and 23 percent of the Chinook salmon that entered the forebay were collected, primarily through collection flumes. The FSC collected a single radio-tagged fish (a Chinook salmon) in 2011.

Washington↗
USGS2012

Evaluation of stream flow effects on smolt survival in the Yakima River basin, Washington

Study Summary The influence of stream flow on salmon smolt emigration survival is a topic of widespread management interest. We collected smolt survival data to inform flow management decisions in the Yakima Basin. The Yakima River watershed drains the eastern slopes of the Cascade Mountain Range in central Washington State. The upper basin is comprised of two major tributaries&ndash;the Naches River and the upper Yakima River. Headwater storage reservoirs capture runoff during the winter and spring seasons to support downstream irrigation needs. During summer months, water is conveyed through the upper Yakima River and diverted at Roza Dam, a major irrigation diversion that supplies water to the Roza Irrigation District and to a hydroelectric plant located near Yakima, Washington. To assess smolt survival in the 18 km reach downstream of Roza Dam, a radio telemetry project will be carried out over a three-year timeframe. The first year of study was designed to provide baseline survival estimates at two distinct flow treatments during the spring migration period. The goal was to establish flow treatments that were as divergent as possible in order to maximize the observed effect of environmental conditions on smolt survival. In total, three experimental trials were carried out in 2012&ndash;one during low flow conditions (<600 cfs) and two during high flows (>3000 cfs). Data from the first year will be used to determine experimental design requirements to adequately address study objectives in years two and three. In the spring of 2012, fixed telemetry monitoring stations were established in strategic locations upstream and downstream of Roza Dam. Yearling Chinook salmon Oncorhynchus tshawytscha smolts originating from Cle Elum Hatchery were captured at the Roza Dam fish screen bypass facility, implanted with radio tags, and released upstream of Roza Dam. Each release group of 50 fish was paired with a high or low flow condition. Fish movements were tracked as tagged fish passed each monitoring station during their migration down the upper Yakima River, through Roza Dam, past the Naches River confluence, and eventually through Sunnyside and Prosser Dams. At the conclusion of field data collection, survival rates for each release group were calculated using Cormack-Jolly-Seber mark-recapture models. Yearling Chinook smolt survival and travel time estimates from 2012 suggest that migration rates and survival rates in the Roza Reach may be associated with stream flow, water temperature, release timing (i.e. migratory disposition), and fish size, but the extent to which each variable influenced survival is yet to be determined. The lowest survival rate (61%) and longest travel time (median 2.26 days) was observed in Release Group 1, which had the smallest size distribution and experienced the lowest flows, lowest temperatures, and earliest release date among the three groups. Release Groups 2 and 3 survived at 96% and 98% respectively and traveled through the Roza Reach in less than eight hours. The primary focus of years two and three of this study will be to collect data that minimizes the effect of confounding explanatory variables, so that flow effects on emigration survival can be quantified independent of these other influential factors.

Washington↗
USGS2011

Water velocity, turbulence, and migration rate of subyearling fall Chinook salmon in the free-flowing and impounded Snake River

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 turbulence but increased to riverine levels again as the fish moved further down in the reservoir, where velocity and turbulence remained low. The migration rate (km/d) decreased in accordance with longitudinal reductions in velocity and turbulence, as predicted by the hypothesis. The variation in migration rate was better explained by a repeatedmeasures regression model containing velocity (Akaike’s information criterion ¼ 1,769.0) than a model containing flow (2,232.6). We conclude that subyearling fall Chinook salmon respond to changes in water velocity and turbulence, which work together to affect the migration rate.

Transactions of the American Fisheries Society↗
USGS2011

Behavior and movement of formerly landlocked juvenile coho salmon after release into the free-flowing Cowlitz River, Washington

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.

Washington↗
USGS2011

Analysis of dam-passage survival of yearling and subyearling Chinook salmon and juvenile steelhead at The Dalles Dam, Oregon, 2010

We performed a series of analyses of mark-recapture data from a study at The Dalles Dam during 2010 to determine if model assumptions for estimation of juvenile salmonid dam-passage survival were met and if results were similar to those using the University of Washington's newly developed ATLAS software. The study was conducted by the Pacific Northwest National Laboratory and used acoustic telemetry of yearling Chinook salmon, juvenile steelhead, and subyearling Chinook salmon released at three sites according to the new virtual/paired-release statistical model. This was the first field application of the new model, and the results were used to measure compliance with minimum survival standards set forth in a recent Biological Opinion. Our analyses indicated that most model assumptions were met. The fish groups mixed in time and space, and no euthanized tagged fish were detected. Estimates of reach-specific survival were similar in fish tagged by each of the six taggers during the spring, but not in the summer. Tagger effort was unevenly allocated temporally during tagging of subyearling Chinook salmon in the summer; the difference in survival estimates among taggers was more likely a result of a temporal trend in actual survival than of tagger effects. The reach-specific survival of fish released at the three sites was not equal in the reaches they had in common for juvenile steelhead or subyearling Chinook salmon, violating one model assumption. This violation did not affect the estimate of dam-passage survival, because data from the common reaches were not used in its calculation. Contrary to expectation, precision of survival estimates was not improved by using the most parsimonious model of recapture probabilities instead of the fully parameterized model. Adjusting survival estimates for differences in fish travel times and tag lives increased the dam-passage survival estimate for yearling Chinook salmon by 0.0001 and for juvenile steelhead by 0.0004. The estimate was unchanged for subyearling Chinook salmon. The tag-life-adjusted dam-passage survival estimates from our analyses were 0.9641 (standard error [SE] 0.0096) for yearling Chinook salmon, 0.9534 (SE 0.0097) for juvenile steelhead, and 0.9404 (SE 0.0091) for subyearling Chinook salmon. These were within 0.0001 of estimates made by the University of Washington using the ATLAS software. Contrary to the intent of the virtual/paired-release model to adjust estimates of the paired-release model downward in order to account for differential handling mortality rates between release groups, random variation in survival estimates may result in an upward adjustment of survival relative to estimates from the paired-release model. Further investigation of this property of the virtual/paired-release model likely would prove beneficial. In addition, we suggest that differential selective pressures near release sites of the two control groups could bias estimates of dam-passage survival from the virtual/paired-release model.

Open-File Report↗
USGS2011

Evaluation of angler effort and harvest of rainbow trout (Oncorhynchus mykiss), Lake Scanewa, Washington, 2010

A creel evaluation was conducted in Lake Scanewa, a reservoir on the Cowlitz River, to monitor catch rates of rainbow trout (Oncorhynchus mykiss) and determine if the trout fishery was having negative impacts on juvenile anadromous salmon (Oncorhynchus spp.) in the system. The trout fishery, which is supported by releases of 20,000 fish (2 fish per pound) per year from June to August, was developed to mitigate for the construction of the Cowlitz Falls Dam in 1994. The trout fishery has a target catch rate of at least 0.50 fish per hour. Interviews with 1,214 anglers during the creel evaluation found that most anglers targeted rainbow trout (52 percent) or Chinook and coho salmon (48 percent). The interviewed anglers caught a total of 1,866 fish, most of which were rainbow trout (1,213 fish; 78 percent) or coho salmon (311 fish; 20 percent). We estimated that anglers spent 17,365 hours fishing in Lake Scanewa from June to November 2010. Catch rates for boat anglers (1.39 fish per hour) exceeded the 0.50 fish per hour target, whereas catch rates for shore anglers (0.35 fish per hour) fell short of the goal. The combined catch rates for all trout anglers in the reservoir were 0.96 fish per hour. We estimated that anglers harvested 7,584 (95 percent confidence interval = 2,795-12,372 fish) rainbow trout during the study period and boat anglers caught more fish than shore anglers (5,975 and 1,609 fish, respectively). This estimate suggests that more than 12,000 of the 20,000 rainbow trout released into Lake Scanewa during 2010 were not harvested, and could negatively impact juvenile salmon in the reservoir through predation or competition. We examined 1,236 stomach samples from rainbow trout and found that 2.1 percent (26 fish) of these samples contained juvenile fish. Large trout (greater than 300 millimeters) had a higher incidence of predation than small trout (less than 300 millimeters; 8.50 and 0.06 percent, respectively). A total of 39 fish were found in rainbow trout stomachs and 13 (33 percent) of these were juvenile salmon. These data and uncertainties associated with movement patterns and survival rates of rainbow trout in Lake Scanewa suggest that future evaluations would be helpful to better understand the potential effects of the mitigation trout fishery on juvenile salmon in the reservoir.

Washington↗
USGS2010

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. The authors, however, could only speculate as to how juvenile salmon use habitat and respond to changes in water level fluctuations. Conversely, in this study we provide data on the diel activities of rearing juvenile wild fall Chinook Salmon which provides a better understanding of how fish “use” these rearing habitats. Diel behavior patterns are important because fish in the Hanford Reach are often stranded on shorelines when the water level rapidly recedes because of hydroelectric power generation at upriver dams (Nugent and others 2002; Anglin and others 2006). We hypothesize that juvenile salmon are at greater risk of stranding at night because they are less active and occupy habitat differently than during the day. We used underwater videography to collect behavioral information during the day and night to determine if juvenile fall Chinook Salmon are more susceptible to stranding when water level fluctuations occur at night.

Northwestern Naturalist↗
USGS2009

Evaluation of strobe lights to reduce turbine entrainment of juvenile steelhead ( Oncorhynchus mykiss ) at Cowlitz Falls Dam, Washington

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.

Northwest Science↗
USGS2007

Migration behavior and dispersal of adult spring Chinook salmon released into Lake Scanewa on the upper Cowlitz River during 2005

During 2005, we conducted a radio-telemetry study to answer a number of basic questions about the migration behavior of adult Spring Chinook salmon (Oncorhynchus tshawytscha) released into the upper Cowlitz River watershed. We also conducted a pilot study of adult Coho salmon (Oncorhynchus kisutch) using radio-tags recovered from adult spring Chinook salmon. This data is included as an Appendix. Our study was designed to evaluate the dispersal of adult spring Chinook salmon to determine the proportion of the run 1) spawning in the Cispus River, 2) spawning in the Cowlitz River, 3) passing downstream through Cowlitz Falls Dam into Riffe Lake, and 4) remaining in Lake Scanewa. We also examined spatial patterns of movement in the study area and temporal patterns of fish movements. Last, we examined differences in migration behavior between hatchery and wild fish and male and female fish.

Washington↗
USGS2007

Investigating passage of ESA-listed juvenile fall Chinook salmon at Lower Granite Dam during winter when the fish bypass system is not operated

During the winter of 2006-07, we radio and passive integrated transponder (PIT) tagged, and released 99 juvenile fall Chinook salmon to evaluate over-wintering behavior and dam passage in the lower Snake River, Washington. All fish were released 10 km upstream of Lower Granite Dam at Granite Point in early November, 2006. Fixed radio telemetry detection sites located in the forebay and tailrace areas of Lower Granite, Little Goose, Lower Monumental, Ice Harbor, Bonneville dams, and at Lyle, Washington were used to monitor fish movements and dam passage through early-May 2007. Of the 99 fish released during our study, 80 passed Lower Granite Dam and were detected at downstream detection sites, 37 passed Little Goose Dam, 41 passed Lower Monumental Dam, 31 passed Ice Harbor Dam, 18 passed Lyle, WA, and 13 passed Bonneville Dam. Of the fish that passed Lower Granite Dam in the fall, 63 fish did so during the extended bypass period from November 1 through December 16. Of these fish, 53 were also detected by the PIT-tag interrogation system. Fifteen of the fish that passed Lower Granite Dam in the fall continued to pass lower Snake River dams and exit the system by the end of January. The remaining fish either died, their tags failed, or they resided in Little Goose Reservoir until spring when relatively few continued their seaward migration. Passage of tagged fish past lower Snake River dams generally declined during the winter as temperatures decreased, but increased again in the spring as temperatures and flows increased. Fish residence times in reservoirs and forebays was lengthy during the winter (up to 160 d), and varied by reservoir and time of year. We observed no diel trends in fish passage. Very few fish were detected at PIT-tag interrogation sites in the spring compared to detection by radio telemetry detection sites indicating that fish may have passed via spill. We believe that passage of overwintering juvenile fall Chinook salmon during winter is due more to chance than directed downstream movement. Since the primary route of passage during the winter is through powerhouse turbines, the potential exists for increased mortality for over-wintering juvenile fall Chinook salmon in the Snake River. Our findings that some fish can pass undetected during the winter likely bias traditional smolt-to-adult return rate calculations that are typically used to measure the success of juvenile transportation studies.

Washington↗