U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2016–1144

Prepared in cooperation with the Public Utility District Number 1 of Lewis County, Washington, 

and the Washington Department of Fish and Wildlife

Behavior Patterns and Fates of Adult Steelhead, Chinook 

Salmon, and Coho Salmon Released into the Upper Cowlitz 

River Basin, 2005–09 and 2012, Washington
Cover: Photograph showing an October sunrise over Pompey Peak in the Upper Cowlitz River Basin, Washington. 

Photograph by Toby Kock, U.S. Geological Survey, October 27, 2008.

 
Behavior Patterns and Fates of Adult Steelhead, Chinook 

Salmon, and Coho Salmon Released into the Upper 

Cowlitz River Basin, 2005–09 and 2012, Washington

By Tobias J. Kock, Brian K. Ekstrom, Theresa L. Liedtke, John D. Serl, and Mike Kohn

Prepared in cooperation with the Public Utility District Number 1 of Lewis County, 

Washington, and the Washington Department of Fish and Wildlife

Open-File Report 2016-1144

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation:

Kock, T.J., Ekstrom, B.K., Liedtke, T.L., Serl, J.D., and Kohn, Mike, 2016, Behavior patterns and fates of adult 

steelhead, Chinook salmon, and coho salmon released into the upper Cowlitz River Basin, Washington, 2005–09 

and 2012: U.S. Geological Survey Open-File Report 2016-1144, 36 p., http://dx.doi.org/10.3133/ofr20161144. 

ISSN 2331-1258 (online)
iii

Contents

Abstract ...................................................................................................................................................................... 1

Introduction................................................................................................................................................................. 2

Methods...................................................................................................................................................................... 5

Fish Collection, Tagging, and Release.................................................................................................................... 5

Telemetry Monitoring Array..................................................................................................................................... 6

River Flows ............................................................................................................................................................. 7

Data Analysis .......................................................................................................................................................... 7

Results........................................................................................................................................................................ 8

River Environment................................................................................................................................................... 8

Steelhead.............................................................................................................................................................. 11

Tagging and Release ........................................................................................................................................ 11

Behavior ............................................................................................................................................................ 13

Fates ................................................................................................................................................................. 15

Kelts .................................................................................................................................................................. 18

Tagging and Release ........................................................................................................................................ 19

Behavior ............................................................................................................................................................ 21

Fates ................................................................................................................................................................. 24

Coho Salmon ........................................................................................................................................................ 26

Tagging and Release ........................................................................................................................................ 26

Behavior ............................................................................................................................................................ 28

Fates ................................................................................................................................................................. 30

Discussion ................................................................................................................................................................ 32

Acknowledgments..................................................................................................................................................... 34

References Cited...................................................................................................................................................... 35
iv

Figures

Figure 1. Map showing locations of fixed telemetry sites used during all years of the study (open circles) 

and some years of the study (gray circles), and places where adult salmon and steelhead were released (stars), 

upper Cowlitz River basin, Washington, 2005–09 and 2012...................................................................................... 3

Figure 2. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, 

during March–June in 2006, 2007, 2008, 2009, and 2012, when behavior of radio-tagged steelhead 

was being monitored.................................................................................................................................................. 9

Figure 3. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, 

during April–October in 2005, 2006, 2007, and 2012, when behavior of radio-tagged Chinook salmon 

was being monitored................................................................................................................................................ 10

Figure 4. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, during 

August–December in 2005, 2006, 2007, 2008, and 2009, when behavior of radio-tagged coho salmon 

was being monitored................................................................................................................................................ 10

Figure 5. Graph showing number of adult steelhead radio-tagged and released in the upper 

Cowlitz River Basin, 2006–09 and 2012 .................................................................................................................. 12

Figure 6. Graph showing survival distribution function of elapsed time from release of radio-tagged adult

steelhead in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 2006–09 and 2012........... 13

Figure 7. Graphs showing relationship between monthly average discharge and percentage of fallback

for monthly release groups of steelhead, Chinook salmon, and coho salmon, upper Cowlitz River Basin, 

Washington, 2005–09 and 2012.............................................................................................................................. 17

Figure 8. Graphs showing number of adult Chinook salmon radio-tagged and released in the upper 

Cowlitz River Basin, Washington, 2005–07 and 2012. ............................................................................................ 20

Figure 9. Graph showing survival distribution function of elapsed time from release of radio-tagged 

adult Chinook salmon in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 

2005–07 and 2012................................................................................................................................................... 23

Figure 10. Graph showing percentage of radio-tagged Chinook salmon that entered the Cowlitz or 

Cispus Rivers after being released into Lake Scanewa, Washington, June–October, 2005–07 and 2012.............. 23

Figure 11. Graphs showing number of adult coho salmon radio-tagged and released in the upper Cowlitz River 

Basin, Washington, 2005–09................................................................................................................................... 27

Figure 12. Graph showing survival distribution function of elapsed time from release of radio-tagged adult coho 

salmon in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 2005–09 .............................. 30
v 

Tables

Table 1. Average monthly discharges in the Cowlitz and Cispus Rivers, Washington, 2005–09 and 2012.............. 8

Table 2. Number of adult steelhead radio-tagged, released, and monitored in the upper Cowlitz River Basin, 

Washington, 2006–09 and 2012.............................................................................................................................. 11

Table 3. Number of adult steelhead detected in Lake Scanewa, Cowlitz River, or Cispus River following 

release at one of three locations in the upper Cowlitz River Basin, Washington, 2006–09 and 2012...................... 14

Table 4. Number of adult steelhead detected in upstream and downstream reaches of the Cowlitz River and 

Cispus River following release in Lake Scanewa, Washington, 2006–09 and 2012 ................................................ 14

Table 5. Median elapsed time from release of radio-tagged adult steelhead to first detection in the 

Cowlitz River, Cispus River, or Lake Scanewa, Washington, 2006–09 and 2012 ................................................... 14

Table 6. Number of trips made by adult steelhead between Lake Scanewa and the Cowlitz River or 

Cispus River, Washington, 2006–09 and 2012........................................................................................................ 15

Table 7. Number of radio-tagged adult steelhead assigned to Cowlitz River, Cispus River, Lake Scanewa, 

and fallback fates, Washington, 2005–09 and 2012 ................................................................................................ 16

Table 8. Percentage of adult steelhead, Chinook salmon, and coho salmon that fell back downstream of 

Cowlitz Falls Dam prior to spawning, Washington, 2005–09 and 2012 ................................................................... 16

Table 9. Percentage of adult steelhead kelts that remained upstream of Cowlitz Falls Dam, that 

were collected at the dam, or that passed downstream of the dam, Washington, 2005–09 and 2012..................... 18

Table 10. Number of adult Chinook salmon radio-tagged, released, and monitored in the upper Cowlitz River 

Basin, Washington, 2005–07 and 2012 ................................................................................................................... 19

Table 11. Number of adult Chinook salmon detected in Lake Scanewa, Cowlitz River, or the Cispus River

ollowing release at one of three locations in the upper Cowlitz River Basin, Washington, 2005–07 and 2012........ 21

Table 12. Number of Chinook salmon that were detected in upstream and downstream reaches of the Cowlitz 

River or Cispus River following release in Lake Scanewa, Washington, 2005–07 and 2012................................... 22

Table 13. Median elapsed time from release of radio-tagged Chinook salmon to first detection in the 

Cowlitz River, Cispus River, or Lake Scanewa, Washington, 2005–07 and 2012 ................................................... 22

Table 14. Number of trips made by Chinook salmon between Lake Scanewa and the Cowlitz River or Cispus 

River, Washington, 2005–07 and 2012.................................................................................................................... 22

Table 15. Number of radio-tagged adult Chinook salmon assigned to Cowlitz River, Cispus River, 

Lake Scanewa, and fallback fates, Washington, 2005–07 and 2012....................................................................... 25

Table 16. Number of adult coho salmon radio-tagged, released, and monitored in the upper Cowlitz 

River Basin, Washington, 2005–09.......................................................................................................................... 26

Table 17. Number of adult coho salmon detected in Lake Scanewa, Cowlitz River, or Cispus River following 

release at one of three locations in the upper Cowlitz River Basin, Washington, 2005–09...................................... 28

Table 18. Number of coho salmon detected in upstream and downstream reaches of the Cowlitz River or 

Cispus River following release in Lake Scanewa, Washington, 2005–09................................................................ 29

Table 19. Median elapsed time from release to first detection of radio-tagged coho salmon in the 

Cowlitz River, Cispus River, or Lake Scanewa, Washington, 2005–09 ................................................................... 29

Table 20. Number of trips made by coho salmon between Lake Scanewa and the Cowlitz River or 

Cispus River, Washington, 2005–09........................................................................................................................ 29

Table 21. Number of radio-tagged adult coho salmon assigned to Cowlitz River, Cispus River,

Lake Scanewa, and fallback fates, Washington, 2005–09....................................................................................... 31
vi 

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

International System of Units to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as: 

°F = (1.8 × °C) + 32.
1 

Behavior Patterns and Fates of Adult Steelhead, Chinook 

Salmon, and Coho Salmon Released into the Upper 

Cowlitz River Basin, 2005–09 and 2012

By Tobias J. Kock1, Brian K. Ekstrom1, Theresa L. Liedtke1, John D. Serl2, and Mike Kohn3

Abstract

A multiyear radiotelemetry evaluation was conducted to monitor adult steelhead (Oncorhynchus 

mykiss), Chinook salmon (O. tshawytscha), and coho salmon (O. kisutch) behavior and movement 

patterns in the upper Cowlitz River Basin. Volitional passage to this area was eliminated by dam 

construction in the mid-1960s, and a reintroduction program began in the mid-1990s. Fish are 

transported around the dams using a trap-and-haul program, and adult release sites are located in Lake 

Scanewa, the uppermost reservoir in the system, and in the Cowlitz and Cispus Rivers. Our goal was to 

estimate the proportion of tagged fish that fell back downstream of Cowlitz Falls Dam before the 

spawning period and to determine the proportion that were present in the Cowlitz and Cispus Rivers 

during the spawning period. Fallback is important because Cowlitz Falls Dam does not have upstream 

fish passage, so fish that pass the dam are unable to move back upstream and spawn. A total of 2,051 

steelhead and salmon were tagged for the study, which was conducted during 2005–09 and 2012, and 

173 (8.4 percent) of these regurgitated their transmitter prior to, or shortly after release. Once these fish 

were removed from the dataset, the final number of fish that was monitored totaled 1,878 fish, including 

647 steelhead, 770 Chinook salmon, and 461 coho salmon. 

Hatchery-origin (HOR) and natural-origin (NOR) steelhead, Chinook salmon, and coho salmon 

behaved differently following release into Lake Scanewa. Detection records showed that the percentage

of HOR fish that moved upstream and entered the Cowlitz River or Cispus River after release was 

relatively low (steelhead = 38 percent; Chinook salmon = 67 percent; coho salmon = 41 percent) 

compared to NOR fish (steelhead = 84 percent; Chinook salmon = 82 percent; coho salmon = 76 

percent). The elapsed time from release to river entry was significantly lower for NOR fish than for 

HOR fish for all three species. Tagged fish entered the Cowlitz River in greater proportions than the 

Cispus River, regardless of origin. We found that 23–47 percent of the HOR fish entered the Cowlitz 

River and 12–38 percent entered the Cispus River. Similarly, 67–70 percent of the NOR fish entered the 

Cowlitz River and 38–66 percent entered the Cispus River. These behavioral differences translated into 

similar differences in fates during the spawning periods as higher percentages of tagged fish were 

assigned Cowlitz River fates than Cispus River fates. 

1

U.S. Geological Survey. 

2

Washington Department of Fish and Wildlife. 

3

Public Utility District Number 1 of Lewis County, Washington.
2 

Fallback rates were affected by fish origin and release site. Overall, 12 percent of steelhead, 19 

percent of Chinook salmon, and 8 percent of coho salmon fell back downstream of Cowlitz Falls Dam 

prior to spawning. Fallback rates were lower for fish that were released in the Cowlitz River or the 

Cispus River than for reservoir-released fish, but statistical comparisons were not robust because of 

small sample sizes at the river release sites. Fallback rates for fish released at the river release sites were 

10 percent lower for steelhead, 4 percent lower for Chinook salmon, and 9 percent lower for coho 

salmon than for reservoir-released fish. However, fallback rates also were different between HOR and 

NOR fish. Fallback rates were significantly higher for HOR reservoir-released fish than for NOR 

reservoir-released fish. 

This study provided data that were insightful for understanding behavior and movement patterns 

in the upper Cowlitz River Basin and yielded estimates of fallback rates and fish fates that may be 

useful for fishery managers in the years to come. Studies from other systems have shown that factors 

such as prespawn mortality and fallback have resulted in substantial losses to spawning populations 

where trap-and-haul programs are being used as a restoration tool. Future research in the upper Cowlitz 

River Basin may use additional telemetry studies, genetic analyses, and spawning ground surveys to 

provide answers for new questions and to continue to monitor the progress of the reintroduction effort. 

Introduction

Many of the dams that were constructed in the Pacific Northwest during the 20th century failed 

to provide upstream fish passage, which eliminated access to important spawning areas for numerous 

anadromous salmonid (Oncorhynchus spp.) populations. By the 1990s, many of these populations had 

declined to levels that necessitated listing as threatened or endangered under the U.S. Endangered 

Species Act (National Marine Fisheries Service, 1999). Efforts to restore salmon runs to areas blocked 

by dams have included the implementation of trap-and-haul programs, installation of fish passage 

devices, population supplementation and reintroduction, and dam removal (Bryant and others, 1999; 

Pearsons and Temple, 2007; Brenkman and others, 2008; Anderson and others, 2014). Trap-and-haul 

programs are common because they do not require dam modifications (which can be expensive), yet still 

provide access for anadromous fish into areas that are blocked. 

In the Cowlitz River, Washington, volitional fish passage was eliminated when Mayfield Dam 

and Mossyrock Dam were constructed (fig. 1) in the 1960s. Mayfield Dam was constructed in 1963 and 

included adult fish passage facilities, but these were not used after 1968 when Mossyrock Dam was 

completed. Mossyrock Dam is the tallest dam in Washington State, and its height created conditions that 

eliminated volitional passage for upstream and downstream fish migrants. Functional fish ladders were 

not possible given the height of the dam, and downstream passage was eliminated because of the size 

and depth of Riffe Lake (fig. 1) and depth of turbines. Two other dams are located on the Cowlitz River, 

and these dams provided the opportunity to implement a trap-and-haul program in 1996 that 

reintroduced anadromous salmonids to the upper Cowlitz River Basin. The Barrier Dam, located 4 km 

downstream of Mayfield Dam, was designed to stop upstream migrants at the location where the 

Cowlitz Salmon Hatchery’s adult fish ladder entrance is located. Adult salmon encounter the Barrier 

Dam as they move upstream and then enter the fish ladder and ascend to a trap where they can be sorted 

and retained for propagation at the hatchery, or loaded onto trucks and transported upstream. Cowlitz 

Falls Dam is located 38 km upstream of Mossyrock Dam and was designed to be easily retrofitted to 

collect downstream migrants after it was completed in 1994, when funding became available (fig. 1). 
3 

Figure 1. Map showing locations of fixed telemetry sites used during all years of the study (open circles) and some 

years of the study (gray circles), and places where adult salmon and steelhead were released (stars), upper 

Cowlitz River basin, Washington, 2005–09 and 2012. Solid line arrows show the locations that delineated the 

boundaries for the upstream and downstream reaches in each river.
4 

The trap-and-haul program has been the cornerstone of efforts to restore steelhead (O. mykiss), 

spring and fall Chinook salmon (O. tshawytscha), and coho salmon (O. kisutch) populations in the upper 

Cowlitz River, Washington, since 1996. Adult salmon and steelhead are collected at the Cowlitz Salmon 

Hatchery and transported upstream to release sites on the Tilton, Cowlitz, and Cispus Rivers (fig. 1).

The primary release site in the upper Cowlitz River is located in Lake Scanewa, the reservoir created 

when Cowlitz Falls Dam was constructed. The confluence of the Cowlitz and Cispus Rivers is near the 

middle of Lake Scanewa (fig. 1), which provides the opportunity for fish to self-select one of these 

rivers for spawning after being released at the Lake Scanewa release site. Providing a site that allowed 

these adult fish to self-select a river, possibly the river of its origin, was among the highest priorities for 

the committee responsible for reintroducing anadromy to the upper Cowlitz River Basin. Two additional 

release sites that were added at a later date are located upstream of Lake Scanewa. One is located on the 

Cowlitz River near the town of Packwood, Washington, 55 km upstream of the Lake Scanewa release 

site (fig. 1). The other site is located on the Cispus River near the mouth of Yellowjacket Creek, 25 km 

upstream of the Lake Scanewa release site (fig. 1). These sites are typically used during summer when 

water temperatures in Lake Scanewa exceed 20 °C. The trap-and-haul program has returned anadromous 

salmonids to 322 km of stream habitat in the upper Cowlitz River Basin, and juvenile salmonid 

collection efforts at Cowlitz Falls Dam have indicated that adult salmon and steelhead are successfully 

spawning and producing progeny that out-migrate from the upper basin. However, little is known about 

behavior patterns, spawning locations, and fates of adult salmon and steelhead following release.

Trap-and-haul programs are in-place at numerous locations in the Pacific Northwest, but only a 

small number of studies have been conducted to evaluate the success of these efforts. The information 

that is available has shown that prespawn mortality rates can be high in some cases, and factors such as 

sex, origin, and release timing can affect the reproductive success of transported fish. For example, in 

the Willamette River Basin during 2009–14, average prespawn mortality rates for female spring

Chinook salmon were greater than 60 percent in Fall Creek and 30 percent in the North Fork Middle 

Fork Willamette River (Naughton and others, 2015). During 2008–11, Sard and others (2015) evaluated 

a trap-and-haul program in the South Fork McKenzie River, Oregon, and showed that reproductive 

success of Chinook salmon was affected by sex, origin, and release date. In that study, male salmon 

were less fit than female salmon, and hatchery-origin (HOR) male Chinook salmon were less fit than 

natural-origin (NOR) male Chinook salmon. Additionally, fish that were transported early in the season 

had greater reproductive success than fish that were transported later in the season. Given these 

findings, evaluation of the Cowlitz River trap-and-haul program is important to understand fish behavior 

patterns following release in the upper Cowlitz River Basin.

A multi-year telemetry study was conducted during 2005–09 and 2012 to describe post-release 

behaviors and fates of adult salmon and steelhead in areas located upstream of Cowlitz Falls Dam. This 

study was conducted cooperatively with the Washington Department of Fish and Wildlife and the Public 

Utility District No. 1 of Lewis County, Washington. Our primary objective was to determine if tagged 

fish moved into mainstem or tributary habitats in the upper Cowlitz and Cispus Rivers during spawning 

periods. This would be a favorable outcome for transported fish because these areas contain habitat 

suitable for spawning in the upper basin. Alternatively, fish could remain in Lake Scanewa, or move 

downstream and pass Cowlitz Falls Dam prior to spawning. These outcomes would be unfavorable 

because Lake Scanewa contains very little suitable spawning habitat for adult salmon and steelhead, and 

Cowlitz Falls Dam does not have an adult fish ladder, so fish that pass downstream of the dam prior to 

spawning are lost to the population. To provide information about differences in fish origin and release 

site locations, our study included releases of HOR and NOR fish, and releases occurred at each of the 

three release sites.
5 

Methods

Fish Collection, Tagging, and Release

Adult salmon and steelhead were collected for tagging at the Cowlitz Salmon Hatchery (rkm 

113.7) downstream of Mayfield Dam on the lower Cowlitz River (fig. 1). The fish trap at the hatchery

operates continuously during periods when adult salmon are migrating. Fish are handled and sorted 

during weekdays by staff from Tacoma Power. Fish were anesthetized to facilitate the sorting process.

Two methods of anesthesia were used during our study—a carbon dioxide bath was used during 2005–

09, and electrosedation (Model EA-1000B, Smith-Root, Inc., Vancouver, Washington) was used in 

2012. An automatic crowder was located inside the fish trap, and an exit chute was located near the top 

of the trap that led to the area where anesthesia was administered. The crowder was used to force groups 

of fish (20–50 fish/group) into the exit chute for a batch application of anesthesia. The carbon dioxide 

bath was created inside an aluminum fish holding tank that was filled with fresh river water at the start 

of each day. Carbon dioxide was then bubbled into the bath during the rest of the day along with a small 

volume of fresh river water to minimize temperature increases in the tank. Each batch of fish was 

submerged in the carbon dioxide bath until they were inactive and then processed. The electrosedation 

system was commissioned in 2010 as part of a series of upgrades to the Cowlitz Salmon Hatchery. 

Groups of fish were crowded into a large holding basket and electrosedation was applied for 

approximately 30 s, after which fish were immobile and ready for sorting. The fish sorting process was 

identical, regardless of the anesthesia method used. Fish were sorted by species and origin and then 

moved into one of eight concrete holding tanks, where they could be transferred to the hatchery for 

spawning or loaded onto fish hauling trucks and transported to upstream release sites. Tagging occurred 

after sorting but before fish were transferred to the holding tanks. 

The fish tagging process was similar during all years of the study. We collected the following 

data for each fish that was tagged—species, origin (natural or hatchery), sex (visually assessed), and 

fork length (centimeters). Once these data were collected, a radio transmitter was gastrically implanted 

using methods described by Keefer and others (2004). Transmitter technologies improved over the 

course of the study period, so we used smaller transmitters that had longer operating life later in the 

study. Two transmitter models were used. During 2005–09, we used MCFT-7A (Lotek© Wireless, Inc.; 

Newmarket, Ontario, Canada) transmitters that were 83 × 16 mm and weighed 13 g in water. During 

2012, we used MCFT-3EM transmitters (Lotek© Wireless, Inc.; Newmarket, Ontario, Canada) that 

were53 × 12 mm and weighed 4.3 g in water. All transmitters emitted a signal every 5 s, and the 

estimated operating life was 296 d for the MCFT-7A transmitters and 528 d for the MCFT-3EM 

transmitters. A single band of silicon tubing (approximately 1-cm long) was placed around the lower 

portion of each transmitter to decrease the likelihood that transmitters were regurgitated (Keefer and 

others, 2004). Following tagging, each fish was transferred to a concrete holding tank where they were 

held (along with untagged fish) overnight to recover from the trapping, sorting, and tagging process. 
6 

On each release day, groups of fish were loaded onto fish hauling trucks for transport to the 

upper Cowlitz River Basin. The loading process consisted of a water-to-water transfer from the holding 

tank to the fish hauling truck. Transport trucks hauled approximately 130 adult salmon or steelhead in 

each load, and tagged fish were transported with untagged fish. Transport time from the Cowlitz Salmon 

Hatchery to the Lake Scanewa release site was approximately 45 min. Transport from the Cowlitz 

Salmon Hatchery to the Cowlitz River and Cispus River release sites was approximately 90 min.

Releases normally occurred in the morning between 09:00 a.m. and 11:00 a.m. Fish were released 

directly from the transport truck into the river at the Lake Scanewa and Cispus River release sites using 

a 1.0-m-long flume that minimized the drop from the truck to the river. At the Cowlitz River release 

site, fish were released through a 3.0-m-long plastic pipe (30.5 cm diameter) that transported water and 

fish from the truck to the river. 

Telemetry Monitoring Array

A series of fixed telemetry monitoring sites (hereinafter “fixed sites”) were deployed to detect 

tagged fish as they moved throughout the study area. Seven fixed sites were used during all years of the 

study and several other sites were used during 1 or more of the years to determine when fish were in the 

Cowlitz River, in the Cispus River, in Lake Scanewa, or when they passed downstream of Cowlitz Falls 

Dam. The seven primary fixed sites were located at the following locations: 

− on the Cowlitz River at rkm 179; 

− in the Cowlitz Arm of Lake Scanewa at rkm 146; 

− on the Cispus River at rkm 25; 

− in the Cispus Arm of Lake Scanewa at rkm 2;

− in the forebay of Cowlitz Falls Dam at rkm 142;

− in the tailrace of Cowlitz Falls Dam at rkm 141; and 

− downstream of Cowlitz Falls Dam at the head of Riffe Lake at rkm 137 (fig. 1). 

The remaining fixed site locations varied among years due to changes in access and improvements in 

our understanding of fish movement patterns. The locations of these fixed sites allowed us to collect 

additional information on fish movement patterns between the primary sites. All fixed site locations that 

were used during the study are presented in figure 1. Each fixed site contained a telemetry receiver 

(Model SRX-600; Lotek© Wireless, Inc., Newmarket, Ontario, Canada) that was connected to one or 

two Yagi antennas. Power was provided by a 12-V battery that was recharged by a solar panel. Based on 

the locations of the fixed sites, we divided the Cowlitz and Cispus Rivers into downstream and upstream 

regions to provide additional information on fish-use patterns (fig. 1). The downstream region of the 

Cowlitz River was approximately 33-rkm long and included the area between rkm 179 and 146. The 

upstream region of the Cowlitz River included the area located upstream of rkm 179. The downstream 

region of the Cispus River was approximately 6-rkm long and included the area between rkm 8 and 2. 

The upstream region of the Cispus River included the area located upstream of rkm 8 (fig. 1) 

Data from fixed site detections were supplemented with mobile tracking detections during most 

years of the study. Mobile tracking took place at least one time per week during 2005, 2006, 2007, and 

2008. These efforts were primarily conducted using a vehicle to drive slowly along roads that bordered 

the rivers and reservoir in the study area while monitoring a telemetry receiver. Additional irregular

mobile tracking efforts during the study were conducted using an inflatable raft, and a helicopter was 

used on two occasions. 
7 

River Flows

River flows in the upper Cowlitz River Basin are monitored by four streamgages operated by the 

U.S. Geological Survey. Two streamgages are located on the Cowlitz River, upstream of Lake Scanewa 

near the towns of Packwood (14226500) and Randle (14231000). The third streamgage is located on the 

Cispus River near the mouth of Yellowjacket Creek (14231900). The fourth streamgage is located at

Cowlitz Falls Dam and is known as the Kosmos streamgage (14233500). Discharge data from the 

Randle, Cispus, and Kosmos streamgages are highly correlated for the following reasons—the Cowlitz 

and Cispus Rivers respond fairly similarly to rainfall and snowmelt events given their proximity to each 

other; and discharge at the Kosmos streamgage is essentially the sum of discharge at the Randle and 

Yellowjacket Creek streamgages. Therefore, in this report, we only present discharge data from the 

Kosmos streamgage.

Data Analysis 

Fish detection records were examined to describe behavior patterns and determine fates of 

individual tagged fish. To accomplish this, we divided the study area into four regions and identified 

dates that were used to demarcate the onset of the spawning period for each species that we studied. The 

four regions were (1) the Cowlitz River, which included the mainstem Cowlitz River and its tributaries 

located upstream of the fixed site at rkm 146; (2) the Cispus River, which included the mainstem Cispus 

River and its tributaries located upstream of the fixed site at rkm 2; (3) Lake Scanewa, which was 

bounded on the downstream end at Cowlitz Falls Dam and at the upstream ends at rkm 146 on the 

Cowlitz River and at rkm 2 on the Cispus River; and (4) Riffe Lake, which was defined as anything 

located downstream of Cowlitz Falls Dam. Dates used to demarcate the onset of spawning for each 

species were March 15 for steelhead, August 1 for spring Chinook salmon (hereinafter “Chinook 

salmon”), and October 24 for coho salmon. These dates were established based on the run timing of

each species and from observations made during redd surveys by the Washington Department of Fish 

and Wildlife (Serl and Morrill, 2010). These dates were used to differentiate between fish behaviors and 

fates that occurred during the prespawning period, or after spawning began. 

We identified the fate of each fish to estimate the proportion (expressed as a percentage) of fish

that were in the Cowlitz River or Cispus River during the spawning period, that remained in Lake 

Scanewa during the spawning period, or that fell back into Riffe Lake prior to spawning. Fish were 

assigned Cowlitz River or Cispus River fates if they were last detected in either river prior to the 

spawning period, or if they were detected in either river during the spawning period. In some cases,

Chinook and coho salmon moved downstream after the onset of the spawning period, and this behavior 

was common for steelhead, which are iteroparous. To account for this, we established a minimum time 

criterion of 4 d, during which a tagged fish had to reside in one of the rivers after the onset of the 

spawning period. The minimum time criterion was established primarily for steelhead because Chinook 

and coho salmon remained in their tributary after spawning occurred. Examination of the telemetry 

records of steelhead showed that some tagged fish spent 4 d in a tributary before moving downstream 

and out of the system. If a tagged fish was present in one of the rivers for at least 4 d after spawning 

began, it was assigned the fate of that river, unless it moved back upstream and entered one of the rivers 

for at least 4 more days. If a tagged fish was in one of the rivers for less than 4 d after the onset of 

spawning, it was not assigned to that fate. Fish were assigned a reservoir fate if they were last detected

in Lake Scanewa prior to the onset of the spawning period, or if they spent less than 4 d in one of the 

rivers before moving downstream and remaining in the reservoir after the onset of the spawning period. 

Fish were assigned a fallback fate if they were detected downstream of Cowlitz Falls Dam prior to the 

onset of the spawning period. For steelhead, we also assigned a second fate to estimate the proportion 
8 

(expressed as a percentage) of fish that moved downstream as kelts. This second fate included four 

possible outcomes—(1) fish that did not move downstream after spawning; (2) fish that moved 

downstream after spawning but remained in Lake Scanewa; (3) fish that moved downstream after 

spawning and were collected at the Cowlitz Falls fish facility; and (4) fish that moved downstream after 

spawning and passed Cowlitz Falls Dam. 

We used a Chi-squared test of independence to assess statistical differences between groups of 

fish when evaluating most metrics that described fish behavior patterns or fates (Sokal and Rohlf, 1996).

We also used an event-time analysis (Allison, 1995) to compare reservoir residence times and upstream 

movements by HOR and NOR fish following release into Lake Scanewa. Event times were censored for 

fish that did not move upstream and censoring was set to 40 d for steelhead, 140 d for Chinook salmon, 

and 80 d for coho salmon. These censoring periods were based on maximum expected time that a given 

fish would spend upstream of Cowlitz Falls Dam prior to the onset of the spawning period. River 

residence times were calculated as the elapsed time from release in the Cowlitz River or Cispus River to 

first detection in Lake Scanewa. We used t-tests to assess statistical differences in fish size metrics 

(Sokal and Rohlf, 1996). Our analyses focused on describing fish behavior patterns and fates and did not 

consider how these metrics were affected by covariates such as discharge or water temperature. Those 

analyses are likely to be completed at a later date using approaches described in Kock and others (2016). 

Results

River Environment

Discharge in the upper Cowlitz River Basin is largely influenced by rainfall and snowmelt 

events. Rainfall is common during November–March, when monthly discharge is typically in the 

2,500–6,000 ft3

/s range (table 1). Snowmelt generally occurs during April–June when river flows peak 

and monthly discharges greater than 7,000 ft3

/s are common. Low-flow periods occur during August, 

September, and October when monthly discharge generally is less than 1,500 ft3

/s (table 1). During our 

study period, annual discharge was lowest during 2005 when discharge was less than 3,000 ft3

/s in 7 of 

the 12 months of the year. Conversely, annual discharge was highest during 2012, when monthly 

discharge exceeded 6,000 ft3

/s during 7 of the 12 months of the year (table 1). 

Table 1. Average monthly discharges in the Cowlitz and Cispus Rivers, Washington, 2005–09 and 2012. 

[Data from U.S. Geological Survey streamgage Cowlitz River near Kosmos, Washington (14233500). SD, standard 

deviation]

Year Average monthly discharges, in cubic feet per second

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

2005 5,452 2,276 2,644 5,273 5,018 2,835 1,771 1,148 926 1,226 4,017 5,350

2006 10,552 5,571 2,702 4,589 8,340 7,051 2,809 1,352 1,013 734 12,020 7,214

2007 5,589 5,173 9,142 4,989 5,903 4,691 2,325 1,228 996 1,501 2,277 5,794

2008 3,047 2,741 3,582 3,019 12,265 10,445 5,716 2,108 1,405 1,116 5,494 2,437

2009 9,410 2,739 2,897 5,424 9,538 7,026 2,468 1,272 1,112 1,558 5,160 4,267

2012 6,170 6,389 5,262 8,210 9,015 8,091 5,271 1,998 1,232 2,839 6,855 6,164

Mean 6,703 4,148 4,372 5,251 8,346 6,690 3,393 1,518 1,114 1,496 5,971 5,204

SD 2,279 1,764 2,535 1,690 2,618 2,652 1,667 421 178 722 3,338 1,665
9 

Adult steelhead are present in the upper Cowlitz River Basin during March–June each year. In 

the years we monitored steelhead, discharge generally was lowest during March and highest during May 

(fig. 2). However, discharge patterns during 2007 were unusual because discharge was highest during 

March and then decreased to around 5,000 ft3

/s during April–June. Discharge during 2012 was highest 

during most months in the years we monitored steelhead, although average monthly discharges in May 

and June 2008 exceeded 10,000 ft3/s (fig. 2).

Adult Chinook salmon spend several months in the upper Cowlitz River Basin each year. Trapand-haul for these fish typically begins in April, and spawning occurs during August–October, so fish 

are exposed to a wide range of discharge conditions during the prespawning and spawning periods. 

Many Chinook salmon are released into the upper Cowlitz River Basin prior to, or during, peak periods 

in May, and they reside in the system throughout summer when discharge is decreasing to the lowest 

levels of the year (fig. 3). During our study period, discharge was highest during 2012 and lowest during 

2005 (fig. 3). During 2006, discharge was relatively high during May and June (7,000 ft3/s or greater), 

and 2007 discharge was similar to 2005 discharge (fig. 3).

Adult coho salmon are transported and released into the upper Cowlitz River Basin during 

autumn and winter. In the years we monitored coho salmon, river discharges were low during August–

October, then highly variable during November–March (fig. 4). Discharge when coho salmon were 

present in the system generally was highest during 2006 and lowest during late-autumn and winter 2008 

(fig. 4). Average monthly discharge ranged from less than 1,000 ft3/s to greater than 12,000 ft3/s when 

coho salmon were being monitored (fig. 4). 

0

2000

4000

6000

8000

10000

12000

14000

Mar Apr May Jun

Discharge (ft3/sec)

Month

2006

2007

2008

2009

2012

Figure 2. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, during 

March–June in 2006, 2007, 2008, 2009, and 2012, when behavior of radio-tagged steelhead was being monitored.

Data from USGS streamgage on the Cowlitz River near Kosmos, Washington (14233500). 
10 

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Apr May Jun Jul Aug Sep Oct

Discharge (ft3/sec)

Month

2005

2006

2007

2012

Figure 3. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, during April–

October in 2005, 2006, 2007, and 2012, when behavior of radio-tagged Chinook salmon was being monitored. 

Data from USGS streamgage on the Cowlitz River near Kosmos, Washington (14233500).

0

2000

4000

6000

8000

10000

12000

14000

Aug Sep Oct Nov Dec Jan Feb Mar

Discharge (ft3/sec)

Month

2005

2006

2007

2008

2009

Figure 4. Graph showing average monthly discharge in the Cowlitz and Cispus Rivers, Washington, during 

August–December in 2005, 2006, 2007, 2008, and 2009, when behavior of radio-tagged coho salmon was being 

monitored. Data from USGS streamgage on the Cowlitz River near Kosmos, Washington (14233500). 
11 

Steelhead

Tagging and Release

A total of 719 steelhead were radio-tagged for the study, but 72 fish (10.0 percent) regurgitated 

their transmitter prior to, or shortly after, release (table 2). The final tagged population included 647 

fish, and these were split almost evenly between males (366 fish; 51 percent) and females (353 fish; 49 

percent). The average length of tagged females was 71.4 cm and the average length of tagged males was 

70.3 cm, which was nearly statistically different (t = 1.86, P = 0.06). The tagged population contained 

slightly more HOR steelhead (387 fish; 53.8 percent) than NOR steelhead (332 fish; 46.2 percent). 

Natural-origin steelhead were larger (average length = 72.6 cm) than HOR steelhead (average length = 

69.2 cm; t = -5.82, P < 0.0001). Most of the tagged fish were released into Lake Scanewa (505 fish; 

78.1 percent), and the remaining fish were released into the Cowlitz River (63 fish; 9.7 percent) or the 

Cispus River (79 fish; 12.2 percent; table 2). Fish were released during March, April, and May (fig. 5). 

Table 2. Number of adult steelhead radio-tagged, released, and monitored in the upper Cowlitz River Basin, 

Washington, 2006–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin fish (NOR). Numbers in parentheses are tagged fish that regurgitated 

their transmitter during transport or at the release site]

Year Lake Scanewa release site Cowlitz River release site Cispus River release site

HOR NOR HOR NOR HOR NOR

2006 46 (18) 90 (12) 0 0 16 (1) 0

2007 34 (6) 35 (4) 0 0 0 0

2008 33 (5) 73 (6) 42 0 38 (1) 0

2009 132 (16) 15 (2) 0 0 0 0

2012 0 43 (1) 0 21 0 25

Total 245 260 42 21 54 25
12 

Figure 5. Graph showing number of adult steelhead radio-tagged and released in the upper Cowlitz River Basin, 

2006–09 and 2012.
13 

Behavior

There were differences in upstream dispersal patterns and in reservoir residence times prior to 

dispersal between HOR and NOR steelhead that were released into Lake Scanewa. We found that 38 

percent of the reservoir-released HOR steelhead moved upstream and entered the Cowlitz River or the 

Cispus River compared to 84 percent of the NOR steelhead. Median elapsed time from release in the 

reservoir to first detection in one of the rivers was 2.5 d for HOR steelhead and 0.9 d for NOR 

steelhead. Event-time analysis showed that there were statistical differences in upstream movement 

patterns between HOR and NOR steelhead (Wilcoxon test χ2 = 151.4, P < 0.0001; fig. 6). The 

percentage of tagged fish entering the Cowlitz River was greater than the percentage of tagged fish 

entering the Cispus River and this pattern did not vary by fish origin (tables 3 and 4). We found that 67 

percent of the reservoir-released NOR steelhead entered the Cowlitz River but only 30 percent of the 

fish moved into the upstream reach of the river (table 4). By comparison, 23 percent of the HOR 

steelhead entered the Cowlitz River and 8 percent entered the upstream reach. River entry events were 

lower for the Cispus River. Twenty-eight percent of the NOR steelhead and 18 percent of the HOR 

steelhead entered the river and the percentage of reservoir-released fish that entered the upper reach was 

low (15 and 7 percent, respectively; table 4). The median elapsed time from release to first detection in 

either river decreased, with increasing release month for HOR and NOR steelhead (table 5). 

Time from release to river entry (d)

0 10 20 30 40

Proportion of fish released

0.0

0.2

0.4

0.6

0.8

1.0

HOR

NOR

Figure 6. Graph showing survival distribution function of elapsed time from release of radio-tagged adult steelhead

in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 2006–09 and 2012. Data include 

hatchery-origin (HOR) and natural-origin (NOR) fish.
14 

Table 3. Number of adult steelhead detected in Lake Scanewa, Cowlitz River, or Cispus River following release at 

one of three locations in the upper Cowlitz River Basin, Washington, 2006–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish in 

each group]

Release site Origin Number released Lake Scanewa Cowlitz River Cispus River

Reservoir HOR 245 245 (100) 56 (23) 44 (18)

NOR 260 260 (100) 173 (67) 74 (28)

Cowlitz River HOR 42 7 (17) 42 (100) 5 (12)

NOR 21 13 (62) 21 (100) 2 (10)

Cispus River HOR 54 11 (20) 1 (2) 54 (100)

NOR 25 12 (48) 5 (20) 25 (100)

Table 4. Number of adult steelhead detected in upstream and downstream reaches of the Cowlitz River and 

Cispus River following release in Lake Scanewa, Washington, 2006–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish in 

each group]

Origin

Number of fish 

released

Cowlitz River Cispus River

Downstream reach Upstream reach Downstream reach Upstream reach

HOR 245 56 (23) 19 (8) 43 (18) 16 (7)

NOR 260 173 (67) 79 (30) 74 (28) 40 (15)

Table 5. Median elapsed time from release of radio-tagged adult steelhead to first detection in the Cowlitz River, 

Cispus River, or Lake Scanewa, Washington, 2006–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Elapsed times were calculated by subtracting the date

and time of first detection in one of the rivers from the date and time of release in Lake Scanewa

Origin Median elapsed time, in days, by month of release

March April May

HOR 10.0 2.7 1.5

NOR 1.9 1.0 0.7
15 

A substantial number of river-released NOR steelhead moved downstream and entered Lake 

Scanewa but most HOR steelhead remained in one of the rivers following release (table 3). Sixty-two 

percent of the NOR steelhead that were released in the Cowlitz River and 48 percent of the NOR fish 

that were released in the Cispus River moved downstream following release and were detected in Lake 

Scanewa. In contrast, only 17 percent of the HOR steelhead that were released in the Cowlitz River and 

20 percent of the fish that were released in the Cispus River moved downstream to the reservoir (table 

3). Most radio-tagged steelhead (99–100 percent) made two or fewer trips between the reservoir and one 

of the rivers prior to spawning (table 6). 

Table 6. Number of trips made by adult steelhead between Lake Scanewa and the Cowlitz River or Cispus River, 

Washington, 2006–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of tagged 

fish from each group]

Number of trips

Lake Scanewa release Cowlitz River release Cispus River release

HOR NOR HOR NOR NOR

0 163 (67) 62 (24) 37 (88) 9 (43) 14 (56)

1 69 (28) 168 (65) 4 (10) 12 (57) 10 (40)

2 10 (4) 25 (10) 1 (2) 0 1 (4)

3 1 (<1) 4 (2) 0 0 0

4 1 (<1) 1 (<1) 0 0 0

5 0 0 0 0 0

6 1 (<1) 0 0 0 0

Fates

Most NOR steelhead that were released into Lake Scanewa had Cowlitz River or Cispus River 

fates, whereas HOR steelhead primarily remained in the reservoir or fell back downstream of Cowlitz 

Falls Dam. We found that 82 percent of the reservoir-released NOR steelhead had Cowlitz River or 

Cispus River fates (tables 7 and 8). In contrast, nearly two-thirds (65 percent) of the HOR steelhead that 

were released into Lake Scanewa had a reservoir or fallback fate (table 7). In total, 22.0 percent of the 

reservoir-released HOR steelhead and 6.9 percent of the reservoir-released NOR steelhead fell back 

downstream of Cowlitz Falls Dam before spawning occurred (table 7). This difference was statistically 

significant (χ

2

 = 23.6, P < 0.0001). Substantial annual variability in fallback rates were observed—HOR 

steelhead fallback ranged from 4.3 to 31.8 percent and NOR fallback ranged from 0.0 to 23.3 percent. 

Fallback was highest for both HOR and NOR steelhead in 2012 (table 7). We visually assessed the 

relationship between average monthly discharge and percentage of fallback for monthly release groups 

of tagged steelhead that were released into Lake Scanewa. This assessment showed that fallback 

generally was higher for groups of fish when monthly discharge was 6,000 ft3

/s or greater (fig. 7). 
16 

Table 7. Number of radio-tagged adult steelhead assigned to Cowlitz River, Cispus River, Lake Scanewa, and 

fallback fates, Washington, 2005–09 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish]

Release site Origin Year Cowlitz River Cispus River Lake 

Scanewa Fallback

Lake Scanewa HOR 2006 28.3 23.9 43.5 4.3

2007 23.5 29.4 23.5 23.5

2008 39.4 27.3 27.3 6.1

2009 8.3 7.6 52.3 31.8

Overall 18.4 16.3 43.3 22.0

Lake Scanewa NOR 2006 62.8 25.5 7.4 4.3

2007 37.1 37.1 20.0 5.7

2008 50.7 38.4 11.0 0.0

2009 40.0 13.3 33.3 13.3

2012 53.5 18.6 4.7 23.3

Overall 53.1 28.8 11.2 6.9

Cowlitz River HOR 2008 92.9 7.1 0 0

Cowlitz River NOR 2012 66.7 9.5 9.5 14.3

Cispus River HOR 2006 0 87.5 12.5 0

2008 0 94.7 2.6 2.6

Overall 0 92.6 5.6 1.9

Cispus River NOR 2012 20.0 72.0 8.0 0

Table 8. Percentage of adult steelhead, Chinook salmon, and coho salmon that fell back downstream of Cowlitz 

Falls Dam prior to spawning, Washington, 2005–09 and 2012. 

[Data from the Cowlitz River and Cispus River release sites were pooled to obtain data shown in the river release sites 

column. Numbers in parentheses are the number of fish in each group]

Species Reservoir release site River release sites

Did not fallback Did fallback Did not fallback Did fallback

Hatchery origin

Steelhead 78 (191) 22 (54) 99 (95) 1 (1)

Chinook salmon 78 (312) 22 (88) 86 (174) 14 (29)

Coho salmon 83 (105) 17 (22) 95 (161) 5 (8)

Natural origin

Steelhead 93 (242) 7 (18) 89 (41) 11 (5)

Chinook salmon 85 (123) 15 (22) 68 (15) 32 (7)

Coho salmon 93 (108) 7 (8) 100 (49) 0 (0)

Hatchery origin and natural origin

Steelhead 86 (433) 14 (72) 96 (136) 4 (6)

Chinook salmon 80 (435) 20 (110) 84 (189) 16 (36)

Coho salmon 88 (213) 12 (30) 96 (210) 4 (8)
17 

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 2000 4000 6000 8000 10000 12000

 

2006

2007

2008

2012

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 2000 4000 6000 8000 10000 12000

 

2005

2006

2007

2012

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 2000 4000 6000 8000 10000 12000

 

2005

2006

2007

2008

2009

Steelhead

Chinook salmon

Coho salmon

Discharge (ft3/sec)

Percent fallback

Figure 7. Graphs showing relationship between monthly average discharge and percentage of fallback for monthly 

release groups of steelhead, Chinook salmon, and coho salmon, upper Cowlitz River Basin, Washington, 2005–09 

and 2012.
18 

Most radio-tagged steelhead that were released into the Cowlitz or Cispus Rivers remained in the 

tributary where they were released (table 7), regardless of origin. We found that 92.9 percent of the 

HOR steelhead and 66.7 percent of the NOR steelhead that were released into the Cowlitz River had 

Cowlitz River fates (table 7). Similarly, 92.6 percent of the HOR steelhead and 72.0 percent of the NOR 

steelhead that were released into the Cispus River had Cispus River fates (table 7). In total, 96 HOR 

steelhead were released into the Cowlitz or Cispus Rivers during the study period, and only 1 of those 

fish (1 percent) fell back downstream of Cowlitz Falls Dam. This fallback rate was significantly lower 

than the fallback rate for HOR steelhead that were released into Lake Scanewa (χ

2

 = 22.4, P < 0.0001; 

table 7). In contrast, 46 NOR steelhead were released at the river release sites and 3 (7 percent) of those 

fish fell back, which was not significantly different from NOR steelhead that were released into Lake 

Scanewa (χ

2

 = 0.01, P = 0.921; table 7). 

Kelts

We found that 11.7 percent of the radio-tagged steelhead fell back downstream of Cowlitz Falls 

Dam prior to spawning, and 33.5 percent of the fish that remained upstream of the dam did not move 

downstream as kelts (table 9). About one-fourth (25.7 percent) of the tagged steelhead moved 

downstream and were last detected in Lake Scanewa as kelts, and 16.5 percent were collected at the

Cowlitz Falls Fish Facility (table 8). The remaining steelhead (12.5 percent) passed downstream of 

Cowlitz Falls Dam. There was no difference in the percentage of HOR fish (63.6 percent) and NOR fish 

(60.4 percent; χ2

 = 0.64, P = 0.419) that moved downstream after spawning. However, a higher 

percentage of female fish (68.3 percent) moved downstream than male fish (55.9 percent; χ2

 = 9.41, P = 

0.002). We determined the percentage of kelts that were collected at the Cowlitz Falls Fish Facility by 

dividing the number of kelts collected by the total number of kelts that remained in Lake Scanewa, were 

collected, or passed the dam after spawning. In total, 30.2 percent of the steelhead kelts were collected 

during our study period. The breakdown by sex and origin of kelts that were collected included the 

following—22.9 percent of male HOR steelhead; 33.7 percent of female HOR steelhead; 30.3 percent of 

male NOR steelhead; and 34.0 percent of female NOR steelhead.

Table 9. Percentage of adult steelhead kelts that remained upstream of Cowlitz Falls Dam, that were collected at 

the dam, or that passed downstream of the dam, Washington, 2005–09 and 2012.

Origin Sex

Percentage of adult steelhead kelts

Fallback prior 

to spawning

Not detected moving 

downstream

Last detected in 

Lake Scanewa

Collected at Cowlitz 

Falls Dam

Fallback after 

spawning

HOR Male 16.6 35.2 31.7 11.1 5.5

Female 15.5 23.9 27.5 20.4 12.7

NOR Male 8.1 43.0 22.2 14.8 11.9

Female 5.8 32.2 19.9 21.1 21.1

Total 11.7 33.5 25.7 16.5 12.5
19 

Chinook Salmon 

Tagging and Release

A total of 842 Chinook salmon were radio-tagged, but 72 fish (8.5 percent) regurgitated their 

transmitter prior to, or shortly after, release (table 10). As a result, the final tagged population was 

comprised of 770 fish that were nearly evenly split between females (396 fish; 51 percent) and males 

(374 fish; 49 percent). Most tagged fish were of hatchery-origin (581 fish; 78 percent; table 9). The 

average size of female Chinook salmon (77.6 cm) was larger (t = 3.52, P = 0.0005) than male Chinook 

salmon (75.8 cm), but there was no size difference between NOR and HOR fish (76.6 and 76.9 cm, 

respectively; t = -0.43, P = 0.665). Seventy-one percent of the tagged Chinook salmon were released 

into Lake Scanewa, 20 percent were released into the Cowlitz River, and 9 percent were released into 

the Cispus River (table 10). Chinook salmon were released during April–August (fig. 8).

Table 10. Number of adult Chinook salmon radio-tagged, released, and monitored in the upper Cowlitz River 

Basin, Washington, 2005–07 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin fish (NOR). Numbers in parentheses are tagged fish that regurgitated 

their transmitter during transport or at the release site]

Year Lake Scanewa release site Cowlitz River release site Cispus River release site

HOR NOR HOR NOR HOR NOR

2005 136 (16) 42 (7) 21 0 21 0

2006 105 (15) 33 (13) 0 0 0 0

2007 51 (7) 42 (5) 50 (2) 0 52 (3) 0

2012 108 (3) 28 59 (1) 22 0 0

Total 400 145 130 22 73 0
20 

Figure 8. Graphs showing number of adult Chinook salmon radio-tagged and released in the upper Cowlitz River 

Basin, Washington, 2005–07 and 2012. 
21 

Behavior

We found distinct differences between HOR and NOR Chinook salmon responses to release in 

Lake Scanewa. In total, 67 percent of the reservoir-released HOR Chinook salmon and 84 percent of the 

NOR Chinook salmon moved upstream and were detected in the Cowlitz River or Cispus River. Median 

elapsed time from reservoir release to river entry was 21.0 d for HOR Chinook salmon and 6.6 d for 

NOR Chinook salmon. These data showed that NOR Chinook salmon were more likely than HOR 

Chinook salmon to move upstream and enter one of the rivers, and the NOR fish initiated upstream 

movement quicker than the HOR fish (Wilcoxon text χ2 = 35.1, P < 0.0001; fig. 9). Tagged Chinook 

salmon were more likely to enter the Cowlitz River than the Cispus River, and this relationship did not 

vary by origin (table 11). Seventy percent of the NOR Chinook salmon and 47 percent of the HOR 

Chinook salmon that were released into Lake Scanewa moved upstream and entered the Cowlitz River 

(table 11). More than one-half of the NOR Chinook salmon (52 percent) and about one-fourth of the 

HOR Chinook salmon (23 percent) entered the upstream reach of the Cowlitz River (table 12). In 

contrast, 26 percent of the NOR Chinook salmon and 38 percent of the HOR Chinook salmon entered 

the Cispus River and the percentage of tagged fish that entered the upstream reach of the river was 18 

and 21 percent, respectively (table 12). Median residence times generally were higher for fish released 

early in the year (April and May) than for fish released in June, July, or August (table 12). Naturalorigin Chinook salmon spent less time in the reservoir before moving upstream than HOR Chinook 

salmon in all release months (table 13). Many of the reservoir-released fish made multiple trips between 

the reservoir and the Cowlitz River or Cispus River during the pre-spawning period, regardless of origin

(table 14). Reservoir-released fish entered the Cowlitz River for spawning earlier than fish that entered 

the Cispus River (fig. 10). Seventy-two percent of the fish that had Cowlitz River fates moved upstream 

of the reservoir during July and August whereas 89 percent of the fish with Cispus River fates entered 

the river during August and September. 

More than one-half of the Cowlitz-released Chinook salmon (HOR = 57 percent; NOR = 59 

percent) moved downstream and entered Lake Scanewa and few of these fish entered the Cispus River 

(14 percent or less; table 11). Forty percent of the HOR Chinook salmon that were released at the 

Cispus River release site were detected in Lake Scanewa and 16 percent of the fish were detected in the 

Cowlitz River. There were no strong trends in river residence times between release month, release 

location, or fish origin (table 13). Many of the river-released fish made multiple trips between the 

Cowlitz River or Cispus River and the reservoir during the pre-spawning period (table 14). 

Table 11. Number of adult Chinook salmon detected in Lake Scanewa, Cowlitz River, or the Cispus River following 

release at one of three locations in the upper Cowlitz River Basin, Washington, 2005–07 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish from 

each release group]

Release site Origin Number released Lake Scanewa Cowlitz River Cispus River

Reservoir HOR 400 400 (100) 187 (47) 153 (38)

NOR 145 145 (100) 102 (70) 37 (25)

Cowlitz River HOR 130 74 (57) 130 (100) 18 (14)

NOR 22 13 (59) 22 (100) 0

Cispus River HOR 73 29 (40) 12 (16) 73 (100)
22 

Table 12. Number of Chinook salmon that were detected in upstream and downstream reaches of the Cowlitz 

River or Cispus River following release in Lake Scanewa, Washington, 2005–07 and 2012.

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish from 

each release group]

Origin

Number of 

fish released

Cowlitz River Cispus River

Downstream reach Upstream reach Downstream reach Upstream reach

HOR 400 187 (47) 92 (23) 153 (38) 83 (21)

NOR 145 102 (70) 76 (52) 37 (26) 26 (18)

Table 13. Median elapsed time from release of radio-tagged Chinook salmon to first detection in the Cowlitz River, 

Cispus River, or Lake Scanewa, Washington, 2005–07 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Elapsed times were calculated from the time of release 

to first detection in the Cowlitz River or Cispus River for fish that were released at the reservoir release site, or first detection 

in the reservoir for fish that were released at the Cowlitz River or Cispus River release sites]

Release site Origin

Median elapsed time, in days, by month of release

April May June July August

Reservoir HOR 43.3 16.9 26.3 9.3 7.2

NOR 11.9 8.6 6.1 3.3 .

Cowlitz River HOR 22.3 24.1 17.7 8.4 .

NOR 39.7 . . . .

Cispus River HOR 3.3 24.2 8.4 . .

Table 14. Number of trips made by Chinook salmon between Lake Scanewa and the Cowlitz River or Cispus 

River, Washington, 2005–07 and 2012.

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of tagged 

fish from each group]

Number of trips

Lake Scanewa release Cowlitz River release Cispus River release

HOR NOR HOR NOR NOR

0 136 (34) 37 (26) 64 (49) 12 (55) 48 (66)

1 152 (38) 75 (52) 33 (25) 6 (27) 15 (21)

2 59 (15) 22 (15) 13 (10) 3 (14) 4 (5)

3 28 (7) 6 (4) 9 (7) 1 (5) 1 (1)

4 16 (4) 4 (3) 7 (5) 0 3 (4)

5 5 (1) 1 (<1) 1 (<1) 0 1 (1)

6 1 (<1) 0 0 0 0

7 1 (<1) 0 1 (<1) 0 1 (1)

8 2 (<1) 0 2 (1) 0 0
23 

Figure 9. Graph showing survival distribution function of elapsed time from release of radio-tagged adult Chinook 

salmon in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 2005–07 and 2012. Data 

include hatchery-origin (HOR) and natural-origin (NOR) fish.

Figure 10. Graph showing percentage of radio-tagged Chinook salmon that entered the Cowlitz or Cispus Rivers 

after being released into Lake Scanewa, Washington, June–October, 2005–07 and 2012.

Time in days from release to river entry (d)

0 20 40 60 80 100 120 140

Proportion of fish detected in river

0.0

0.2

0.4

0.6

0.8

1.0

HOR

NOR

Percent of fish

0

10

20

30

40

50

60

Month of tributary entry
24 

Fates

Reservoir-released Chinook salmon did not have a predominant fate and substantial variability 

was observed between fish of different origins and during different study years. The largest percentage

of reservoir-released HOR Chinook salmon (30.8 percent) had Cispus River fates and the smallest

percentage (18.8 percent; table 15) had Cowlitz River fates. Approximately one-third of the HOR 

Chinook salmon had Cispus River fates during each year of the evaluation, but the percentage of fish

with Cowlitz River fates ranged from 9.8 percent in 2007 to 24.3 percent in 2005. The sum of Cowlitz 

River and Cispus River fates for reservoir-released HOR Chinook salmon was 49.6 percent (table 15). 

Fallback rates for HOR Chinook salmon were 22.0 percent overall and ranged from 13.2 percent in 

2005 to 45.1 percent in 2007 (tables 8and 15). The largest percentage of reservoir-released NOR 

Chinook salmon (37.9 percent) had Cowlitz River fates and the smallest percentage (15.2 percent; table 

15) had fallback fates. During 2007, more than one-half (57.1 percent; table 15) of the NOR Chinook 

salmon that were released into the reservoir had Cowlitz River fates, but only 21.4 percent of the fish 

had this same fate in 2005. A higher percentage of reservoir-released HOR Chinook salmon (22 percent) 

had fallback fates than NOR Chinook salmon (15 percent; table 15) but this difference was not 

statistically significant (χ2

 = 3.08, P = 0.08). We visually assessed the relationship between monthly 

average discharge and percentage of fallback for monthly release groups of tagged Chinook salmon that 

were released into Lake Scanewa. This assessment showed that fallback generally was low for groups of 

fish when monthly discharge was less than 3,000 ft3/s (fig. 7). However, fallback rates increased with 

increasing discharge within the discharge range of 4,000 to 9,000 ft3

/s (fig. 7).

Releases of tagged Chinook salmon into the Cowlitz River or Cispus River resulted in higher 

percentages of fish having fates located upstream of Lake Scanewa. We found that 60.8 percent of the 

HOR Chinook salmon and 50.0 percent of the NOR Chinook salmon that were released into the Cowlitz 

River had that fate when the study concluded (table 14). The remaining Cowlitz-released HOR Chinook 

salmon had fallback (15.4 percent), reservoir (12.3 percent), and Cispus River (11.5 percent) fates. The 

remaining Cowlitz-released NOR Chinook salmon had fallback (31.8 percent) and Lake Scanewa (18.2 

percent; table 15) fates. We only released HOR Chinook salmon into the Cispus River and found that 

74.0 percent of those fish had Cispus River fates, while the rest of the fish had Lake Scanewa (12.3 

percent), fallback (12.3 percent), and Cowlitz River fates (1.4 percent; table 15). Fallback rates for riverreleased fish (16.0 percent) were lower than for reservoir-released fish (20.2 percent) but this difference 

was not significant (χ2 = 1.81, P = 0.18). 
25 

Table 15. Number of radio-tagged adult Chinook salmon assigned to Cowlitz River, Cispus River, Lake Scanewa, 

and fallback fates, Washington, 2005–07 and 2012. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish] 

Release site Origin Year

Fate

Cowlitz River Cispus River Lake Scanewa Fallback

Lake Scanewa HOR 2005 24.3 28.7 33.8 13.2

2006 21.0 30.5 24.8 23.8

2007 9.8 33.3 11.8 45.1

2012 13.9 32.4 33.3 20.4

Overall 18.8 30.8 28.5 22.0

Lake Scanewa NOR 2005 21.4 23.8 50.0 4.8

2006 30.3 33.3 18.2 18.2

2007 57.1 21.4 9.5 11.9

2012 42.9 17.9 7.1 32.1

Overall 37.9 24.1 22.8 15.2

Cowlitz River HOR 2005 76.2 0.0 23.8 0.0

2007 62.0 16.0 4.0 18.0

2012 54.2 11.9 15.3 18.6

Overall 60.8 11.5 12.3 15.4

Cowlitz River NOR 2012 50.0 0.0 18.2 31.8

Cispus River HOR 2007 1.4 74.0 12.3 12.3
26 

Coho Salmon

Tagging and Release

A total of 490 coho salmon were tagged during 2005–09. However, 29 fish (5.9 percent) 

regurgitated their radio transmitter prior to, or shortly after, release (table 16). As a result, the final 

tagged population of coho salmon included a total of 461 fish. Of those, 306 (66.3 percent) were HOR 

fish and 184 (39.9 percent) were NOR fish. Hatchery-origin coho salmon averaged 74.1 cm total length 

which was significantly larger than NOR coho salmon (average total length = 72.6 cm total length; t = 

2.37, P = 0.02). We tagged 332 female (72.0 percent) coho salmon and 129 (28.0 percent) male coho 

salmon during the study. Male coho salmon (74.3 cm average) were slightly larger than female coho 

salmon (73.2 cm average), but these differences were not statistically significant (t = -1.72, P = 0.09). 

About one-half of the tagged fish (54.3 percent) were released into Lake Scanewa and the remaining 

fish were released in the Cowlitz River (24.7 percent) or Cispus River (13.9 percent; table 16). Tagged 

fish were released during October–January (fig. 11). 

Table 16. Number of adult coho salmon radio-tagged, released, and monitored in the upper Cowlitz River Basin, 

Washington, 2005–09. 

[Data include hatchery-origin (HOR) and natural-origin fish (NOR). Numbers in parentheses are tagged fish that regurgitated 

their transmitter during transport or at the release site]

Year Lake Scanewa release site Cowlitz River release site Cispus River release site

HOR NOR HOR NOR HOR NOR

2005 20 39 (3) 0 0 0 0

2006 28 (1) 0 26 0 26 (1) 0

2007 0 68 (13) 0 0 12 (3) 22 (1)

2008 35 (4) 27 (2) 36 15 30 13

2009 49 0 44 (1) 0 0 0

Total 132 134 106 15 68 35
27 

Number of fish released

Release date

Figure 11. Graphs showing number of adult coho salmon radio-tagged and released in the upper Cowlitz River 

Basin, Washington, 2005–09. Two fish were tagged and released on August 3, 2007, and are not shown in this 

figure.
28 

Behavior

There were distinct differences in the behavior of HOR and NOR coho salmon following release 

into Lake Scanewa. We found that 41 percent of the reservoir-released HOR coho salmon moved 

upstream and were detected in the Cowlitz River or the Cispus River. In contrast, 76 percent of the NOR 

coho salmon moved upstream into one of the rivers. The HOR coho salmon also took longer to move 

upstream than the NOR coho salmon. Median time in the reservoir prior to upstream movement was 9.6 

d for HOR fish and 5.4 d for NOR fish. These differences were statistically significant (Wilcoxon text χ2

= 39.8, P < 0.0001; fig. 12). Both HOR and NOR coho salmon used the Cowlitz River in greater 

proportions than the Cispus River. Thirty percent of the HOR coho salmon that were released into Lake 

Scanewa were detected in the Cowlitz River compared to 12 percent in the Cispus River (table 17).

Seventy percent of the reservoir-released NOR coho salmon were detected in the Cowlitz River and 10 

percent were detected in the Cispus River. Very few of the reservoir-released coho salmon entered the 

upstream reach of the Cispus River (HOR fish = 3 percent; NOR fish = 7 percent; table 18). Seventeen 

percent of the HOR coho salmon that were released into Lake Scanewa were detected in the upstream 

reach of the Cowlitz River compared to 41 percent of the NOR coho salmon. Median elapsed time from 

reservoir release to river entry generally decreased with increasing release month (table 19) and most 

coho salmon made one or less trips between the reservoir and one of the rivers (table 20).

Few of the radio-tagged coho salmon released into the Cowlitz River or the Cispus River moved 

downstream and entered Lake Scanewa. Only 15 percent of the HOR coho salmon that were released 

into the Cowlitz River moved downstream into Lake Scanewa (table 17). All Cowlitz-released NOR 

coho salmon remained in the Cowlitz River. A small number (two HOR coho salmon; six NOR coho 

salmon) of the Cispus-released coho salmon moved downstream and entered Lake Scanewa. Both of the 

HOR coho salmon, and three of the NOR coho salmon then moved upstream and were detected in the 

Cowlitz River (table 17). Most (94–100 percent) of the tagged coho salmon made one or less trips 

between the reservoir and the Cowlitz River or the Cispus River (table 20).

Table 17. Number of adult coho salmon detected in Lake Scanewa, Cowlitz River, or Cispus River following

release at one of three locations in the upper Cowlitz River Basin, Washington, 2005–09. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish from 

each release group]

Release site Origin Number released Lake Scanewa Cowlitz River Cispus River

Reservoir HOR 127 127 (100) 38 (30) 15 (12)

NOR 116 116 (100) 81 (70) 12 (10)

Cowlitz River HOR 105 16 (15) 105 (100) 0

NOR 15 0 15 (100) 0

Cispus River HOR 64 1 (2) 1 (2) 64 (100)

NOR 34 2 (6) 1 (3) 34 (100)
29 

Table 18. Number of coho salmon detected in upstream and downstream reaches of the Cowlitz River or Cispus 

River following release in Lake Scanewa, Washington, 2005–09. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of fish from 

each release group]

Origin Number of 

fish released

Cowlitz River Cispus River

Downstream reach Upstream reach Downstream reach Upstream reach

HOR 127 38 (30) 22 (17) 15 (12) 4 (3)

NOR 145 81 (70) 47 (41) 12 (10) 8 (7)

Table 19. Median elapsed time from release to first detection of radio-tagged coho salmon in the Cowlitz River, 

Cispus River, or Lake Scanewa, Washington, 2005–09. 

[Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Elapsed times were calculated from the time of release 

to first detection in the Cowlitz River or Cispus River for fish that were released at the reservoir release site, or from first 

detection in the reservoir for fish that were released at the Cowlitz River or Cispus River release sites]

Release site Origin Median elapsed time, in days, by month of release

October November December January

Reservoir HOR 18.6 6.5 6.5 0

NOR 9.6 6.1 4.4 1.4

Cowlitz River HOR 0 20.3 2.8 0

Cispus River HOR 8.4 0 0 0

NOR 0 11.4 29.2 0

Table 20. Number of trips made by coho salmon between Lake Scanewa and the Cowlitz River or Cispus River, 

Washington, 2005–09. 

Data include hatchery-origin (HOR) and natural-origin (NOR) fish. Numbers in parentheses are the percentage of tagged fish 

from each group]

Number of trips Lake Scanewa release Cowlitz River release Cispus River release

HOR NOR HOR NOR HOR NOR

0 91 (72) 70 (60) 94 (90) 15 (100) 63 (98) 32 (94)

1 35 (28) 39 (34) 7 (7) 0 1 (2) 2 (6)

2 0 7 (6) 4 (3) 0 0 0

3 1 (1) 0 0 0 0 0
30 

Time from release to river entry (d)

0 20 40 60 80

Proportion of fish released

0.0

0.2

0.4

0.6

0.8

1.0

HOR

NOR

Figure 12. Graph showing survival distribution function of elapsed time from release of radio-tagged adult coho 

salmon in Lake Scanewa to entry in the Cowltiz River or Cispus River, Washington, 2005–09. Data include 

hatchery-origin (HOR) and natural-origin (NOR) fish. 

Fates

The largest percentage of HOR coho salmon that were released into Lake Scanewa had reservoir 

fates while the largest percentage of NOR coho salmon released into Lake Scanewa had Cowlitz River 

fates. We found that 43.3 percent of the HOR coho salmon released into Lake Scanewa had reservoir 

fates, followed by Cowlitz River (27.6 percent), fallback (17.3 percent), and Cispus River (11.8 percent) 

fates (table 21). Conversely, more than one-half of the NOR coho salmon (53.4 percent) that were 

released into Lake Scanewa had Cowlitz River fates, followed by reservoir (30.2 percent), Cispus River 

(9.5 percent), and fallback fates (6.9 percent). The percentage of HOR coho salmon (17.3 percent) with 

fallback fates was higher (χ2

 = 6.09, P < 0.01) than the percentage of NOR coho salmon (6.9 percent), 

for fish that were released into Lake Scanewa. Although fallback percentages varied by year, HOR 

fallback exceeded 15 percent during most years whereas NOR fallback was less than 10 percent in all 

years when coho salmon were studied (table 8). We visually assessed the relationship between monthly 

average discharge and percentage of fallback for monthly release groups of tagged coho salmon that 

were released into Lake Scanewa. This assessment showed little evidence for a discharge/fallback 

relationship (fig. 7).
31 

Most tagged coho salmon that were released into the Cowlitz River or Cispus River remained in 

those rivers after release (table 21). We found that 85.7 percent of the HOR coho salmon and 100.0 

percent of the NOR coho salmon that were released into the Cowlitz River had Cowlitz River fates 

(table 21). Similarly, 96.9 percent of the HOR coho salmon and 94.1 percent of the NOR coho salmon 

that were released into the Cispus River had Cispus River fates (table 21). We compared fallback rates 

between coho salmon that were released into the rivers (3.7 percent) against those that were released 

into Lake Scanewa (12.3 percent) and found that fallback was lower for river-released fish (χ

2

 = 11.4, P 

< 0.0007; table 21).

Table 21. Number of radio-tagged adult coho salmon assigned to Cowlitz River, Cispus River, Lake Scanewa, and 

fallback fates, Washington, 2005–09. 

[Data are presented for hatchery-origin (HOR) and natural-origin (NOR) fish]

Release site Origin Year Fate

Cowlitz River Cispus River Lake Scanewa Fallback

Reservoir HOR 2005 45.0 5.0 50.0 0

2006 25.9 18.5 33.3 22.2

2008 45.2 22.6 16.1 16.1

2009 10.2 4.1 63.3 22.4

Overall 27.6 11.8 43.3 17.3

Reservoir NOR 2005 58.3 8.3 27.8 5.6

2007 49.1 10.9 30.9 9.1

2008 56.0 8.0 32.0 4.0

Overall 53.4 9.5 30.2 6.9

Cowlitz River HOR 2006 100.0 0 0 0

2008 100.0 0 0 0

2009 65.1 0 18.6 16.3

Overall 85.7 0 7.6 6.7

Cowlitz River NOR 2008 100.0 0 0 0

Cispus River HOR 2006 0 96.0 0 4.0

2007 11.1 88.9 0 0

2008 0 100.0 0 0

Overall 1.6 96.9 0 1.6

Cispus River NOR 2007 0 100.0 0 0

2008 7.7 84.6 7.7 0

Overall 2.9 94.1 2.9 0
32 

Discussion

This study used radiotelemetry to evaluate responses of adult steelhead, Chinook salmon, and 

coho salmon to a trap-and-haul program in the upper Cowlitz River Basin. Research on trap-and-haul 

programs has been fairly limited, but the available information has shown that prespawn mortality and 

fallback rates can be relatively high, and that spawning success is affected by factors such as sex, origin, 

and release date (O’Malley and others, 2014; Naughton and others, 2015; Sard and others, 2015). Data 

collected during this study were insightful for understanding how adult steelhead and salmon move 

within the upper Cowlitz River Basin following transport and for providing estimates on the proportion 

of transported fish that remain in the Cowlitz and Cispus Rivers at the onset of the spawning period. 

Hatchery-origin and NOR fish had distinctly different behavioral responses to release in the 

upper Cowlitz River Basin, and these responses were similar for all species that were studied. We found 

that 38–66 percent of the HOR steelhead, Chinook salmon, and coho salmon that were released into 

Lake Scanewa eventually moved upstream and entered either the Cowlitz River or the Cispus River, but 

this was substantially lower than NOR steelhead, Chinook salmon, and coho salmon, which ranged from 

76 to 84 percent. Hatchery-origin fish also remained in Lake Scanewa longer than NOR fish before 

moving upstream. These behavioral differences translated into differences in fish distributions during 

the spawning period as well. Less than one-half (35–49 percent) of the reservoir-released HOR fish had 

Cowlitz River or Cispus River fates, whereas most (62–82 percent) of the reservoir-released NOR fish 

were assigned to one of the river fates during the spawning period. Our results support other studies that 

have shown that HOR steelhead and salmon are less fit in the wild than NOR steelhead or salmon 

(Christie and others, 2014; Sard and others, 2015). Although many hypotheses are still being tested 

regarding the causal mechanisms for this relationship (Hankin and others, 1993; Theriault and others, 

2011; Ford and others; 2012; Milot and others, 2013), our data suggest that behavioral differences play a 

role. 

Tagged fish used the Cowlitz River in higher proportions than the Cispus River, and this 

relationship did not vary by species or origin. Data collected from radio-tagged fish that were released 

into Lake Scanewa showed that fish were more likely to enter the Cowlitz River than the Cispus River.

We found that 67–70 percent of the NOR steelhead and salmon were detected in the Cowlitz River, 

while only 23–47 of those fish were detected in the Cispus River. The relationship was the same for 

HOR steelhead and salmon, although the proportion of fish in each river was lower: 23–47 percent of 

the HOR fish entered the Cowlitz River while 12–38 percent entered the Cispus River. These data show 

that steelhead and salmon tend to select the Cowlitz River more than the Cispus River, and data from 

the NOR fish indicate that production is higher in the Cowlitz River. More than one-half of the NOR 

steelhead and coho salmon (53 percent each) that were released into Lake Scanewa had Cowlitz River 

fates, as did 38 percent of the NOR Chinook salmon. In contrast, only 29 percent of the NOR steelhead, 

24 percent of the NOR Chinook salmon, and 10 percent of the NOR coho salmon had Cispus River 

fates. This trend will be interesting to follow in the coming years. The reintroduction effort to the upper 

Cowlitz River Basin has only been in place since the mid-1990s so these relationships could change 

substantially as steelhead and salmon populations expand throughout the available habitat in the system. 
33

Tagged fish that were released at the Cowlitz River or Cispus River release sites were less likely 

to fallback downstream of Cowlitz Falls Dam than fish that were released into Lake Scanewa. Data 

from the river release sites was less robust than from the reservoir release sites because fewer fish were 

released in fewer years at those locations. However, the trends in fallback rates from the available data 

are compelling. Annual estimates of fallback for reservoir-released steelhead and coho salmon often 

exceeded 10 percent and were greater than 20 percent in some years, whereas fallback estimates for 

river-released steelhead and coho salmon were less than 5 percent during most years. Fallback estimates 

were generally highest for Chinook salmon, which typically reside in the upper Cowlitz River Basin for 

several months prior to spawning. Annual fallback estimates for Chinook salmon often exceeded 15 

percent regardless of release site, but within-year comparisons indicate that benefits are possible when 

river-release sites are used. In 2007, the fallback estimate for reservoir-released HOR Chinook salmon 

was 45 percent, and the estimates for Cowlitz River and Cispus River releases of HOR Chinook salmon 

were 18 and 12 percent, respectively. The river release sites also resulted in substantially higher 

estimates of river fates for tagged steelhead and salmon, particularly those of hatchery-origin. Annual 

estimates of river fates for steelhead ranged from 8 to 63 percent for reservoir-released fish, while 

Cowlitz River and Cispus River releases had fate estimates in those rivers that ranged from 67 to 93 

percent. The trends generally were the same for Chinook salmon and coho salmon and in several years 

all river-released coho salmon were assigned a fate of the same river where they were released.

This study showed that substantial losses can occur to populations of adult steelhead and salmon 

after release in the upper Cowlitz River Basin. During the course of the study, we found that 18–48 

percent of the tagged fish (by species and origin) either remained in Lake Scanewa or fell back 

downstream of Cowlitz Falls Dam. There is little or no spawning habitat in the reservoir and fish that 

fallback downstream of the dam cannot move back into the upper Cowlitz River Basin because the dam 

does not have a fish ladder for upstream passage. Therefore, our findings indicate that about one-fifth to 

one-half of the transported fish failed to move into the Cowlitz River or Cispus River during the 

spawning period. Similar losses have been documented in other systems. Naughton and others (2015) 

reported that average prespawn mortality rates during 2009–14 for female Chinook salmon exceeded 60 

percent in Fall Creek and were about 30 percent in the North Fork Middle Fork Willamette River, 

Oregon, following trap-and-haul transport. Studies have also documented significant fallback rates for 

adult steelhead and salmon that are released upstream of dams. In Foster Reservoir, Oregon, Naughton 

and others (2015) found that 12 and 23 percent of their tagged Chinook salmon fell back downstream of 

Foster Dam during 2012 and 2013, respectively. These results demonstrate the importance of 

conducting evaluations that assess trap-and-haul operations to understand loss rates that occur after fish 

are released. This study provided baseline information on movement patterns and loss rates, but 

additional research may be required to improve our understanding of the current status of the 

reintroduction program in the upper Cowlitz River Basin.
34

The fate estimates made in this study provide insights into dispersal and loss patterns in the 

upper Cowlitz River Basin, but our study design did not directly assess factors such as prespawn 

mortality, harvest, or spawning success. The telemetry array and mobile tracking methods that were 

used during this study focused on identifying coarse movement patterns and determining fallback rates 

in the study area. The results obtained are informative, but estimates of Cowlitz River, Cispus River, 

and reservoir fates are likely biased because we were not able to assess prespawn mortality, harvest, and 

spawning success. Cowlitz River and Cispus River fates almost certainly overestimate the proportion of 

fish that spawn in these rivers because some fish likely died prior to spawning due to natural factors (for 

example, disease, predation) or harvest by anglers. Additionally, it is unlikely that all fish that survived 

to the onset of the spawning period were successful at spawning, so the proportion of transported fish 

that were successful spawners is likely lower than what was estimated using our study design. The 

estimates of fallback probably are less biased, however, because we were able to detect fish within 

minutes of their fallback event, and we have a good understanding of when the onset of spawning 

occurs for each of the species that we studied. 

This study provided data that were insightful for understanding behavior and movement patterns 

of adult salmon and steelhead in the upper Cowlitz River Basin. The research effort yielded estimates of 

fallback rates and fish fates that may be useful for fishery managers in the years to come. Future 

research in the upper Cowlitz River Basin may use additional telemetry studies, genetic analyses, and 

spawning ground surveys to provide additional insights into the progress of the reintroduction effort. 

Acknowledgments

We are particularly grateful to Wade Heimbigner with the Pacific States Marine Fisheries 

Commission for his efforts with fish tagging, tag recoveries, and mobile tracking during the study. 

Additionally, we thank Tacoma Power for transporting and releasing all tagged fish during the study. 

Numerous private landowners throughout the upper Cowlitz River Basin provided access for fixed sites 

and mobile tracking and we sincerely appreciate their cooperation. Finally, we thank our colleagues at 

the Columbia River Research Laboratory for their efforts with fieldwork during the study. This 

document was reviewed by Rachel Reagan and Brady Allen, and revisions based on their comments 

improved the quality of the final document.
35

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Publishing support provided by the U.S. Geological Survey

Science Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the

 Director, Western Fisheries Research Center

U.S. Geological Survey

6505 NE 65th Street

Seattle, Washington 98115 

http://wfrc.usgs.gov/
Kock and others—Behavior Patterns and Fates of Adult Steelhead, Chinook Salmon, and Coho Salmon Released into the Upper Cowlitz River Basin, Washington—Open-File Report 2016–1144

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20161144