Adult Spring Chinook Salmon Monitoring in Clear Creek, California: 2007 Annual Report. BC/Clear Creek Monitoring... · 2017. 11. 16. · weir to spatially separate SCS and fall Chinook

Adult Spring Chinook Salmon Monitoring in

Clear Creek, California:

2007 Annual Report.

USFWS Report

Prepared by:

Sarah Giovannetti

Matthew R. Brown

U.S. Fish and Wildlife Service

Red Bluff Fish and Wildlife Office

Red Bluff, California 96080

September 2008

ii

Disclaimer

The mention of trade names or commercial products in this report does not constitute

endorsement or recommendation for use by the federal government.

The correct citation for this report is:

Giovannetti, S. L., and M. R. Brown. 2008. Adult spring Chinook salmon monitoring in Clear

Creek, California: 2007 annual report. USFWS Report. U.S. Fish and Wildlife Service,

Red Bluff Fish and Wildlife Office, Red Bluff, California.

iii

Adult Spring Chinook Salmon Monitoring in

Clear Creek, California

2007

Sarah L. Giovannetti

Matthew R. Brown

U.S. Fish and Wildlife Service

Red Bluff Fish and Wildlife Office

10950 Tyler Road

Red Bluff, California 96080

Abstract.—-Central Valley spring Chinook salmon (Oncorhynchus tshawytscha) (SCS)

are listed as a threatened species under the federal Endangered Species Act. Restoration actions

on Clear Creek targeted for the recovery of this species include dam removal, increased instream

flows, and spawning gravel supplementation. To evaluate the effectiveness of these actions, we

used snorkel surveys to monitor adult SCS in Clear Creek since 1999. In addition, to help

reestablish the SCS population in Clear Creek, we installed and monitored a temporary picket

weir to spatially separate SCS and fall Chinook salmon (FCS). This report summarizes results

from 2007.

The SCS August snorkel survey index was 194 in 2007; the highest since monitoring

began. We placed the weir at the Shooting Gallery site from August 23-November 1.

Monitoring results showed the weir remained fish tight, effectively separating FCS from SCS

during spawning, preventing hybridization and redd superimposition. Upstream of the weir, the

SCS snorkel survey redd count was 49. The first redds were observed on September 11 and redd

counts peaked during the last week of September. Thirty-five percent of redds contained

supplemental spawning gravel. Average pre-redd depth was 1.93 ft; average pre-redd water

velocity was 2.3 ft/s. Median substrate size was 1 to 2 inches. We counted 72 carcasses

upstream of the weir during snorkel surveys and weir monitoring. Forty-two percent of the

carcasses were recovered on the weir. Based on carcass recoveries, the male to female sex ratio

was 2.1:1, which may explain the low number of redds compared to the August snorkel survey

index upstream of the weir. Eighty-two percent of the male carcasses were jacks (<610 mm)

(median fork length 503 mm). Age was estimated by reading scales and the majority of the SCS

were 3-year-olds (67%), followed by 2-year-olds (31%). We recovered one coded-wire tag,

which was a Feather River Hatchery SCS, brood year 2004.

Water temperature monitoring demonstrated that it is feasible, using managed flow

releases, to provide suitable conditions between Whiskeytown Dam and the USGS Igo gaging

station for all life stages of SCS. In 2007, flows ranging from 71-97 cubic feet per second (cfs)

maintained temperatures ≤60°F for adult holding and juvenile rearing from June 1 through

September 14. As in previous years, flows >150 cfs were required to consistently meet the

≤56°F spawning criteria beginning on September 14.

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Table of Contents

Abstract .......................................................................................................................................... iii

Table of Contents ......................................................................................................................... iv

List of Tables ................................................................................................................................ vi

List of Figures .............................................................................................................................. vii

Introduction ....................................................................................................................................1

Study Area ......................................................................................................................................1

Methods ...........................................................................................................................................2

Snorkel survey ............................................................................................................................. 2

Survey timing .......................................................................................................................... 2

Survey technique. .................................................................................................................... 3

Environmental conditions ....................................................................................................... 3

Live ......................................................................................................................................... 3

Redds....................................................................................................................................... 3

Redd characteristics ............................................................................................................ 3

Gravel injection ................................................................................................................... 4

Redd distribution ................................................................................................................. 4

Carcasses. ................................................................................................................................ 4

Age structure. ...................................................................................................................... 4

Temporary picket weir installation and monitoring ................................................................... 5

Location and operation dates .................................................................................................. 5

Construction. ........................................................................................................................... 5

Monitoring .............................................................................................................................. 5

Creek flow and water temperature ............................................................................................. 6

Redd temperature exposure..................................................................................................... 6

Results .............................................................................................................................................6

Snorkel surveys ........................................................................................................................... 6

Live ......................................................................................................................................... 6

Redds....................................................................................................................................... 6

Carcasses. ................................................................................................................................ 7

Snorkel carcass recovery..................................................................................................... 7

Weir carcass recovery ......................................................................................................... 7

Bio-sampling ....................................................................................................................... 7

Age structure. ...................................................................................................................... 8

Temporary picket weir installation and monitoring ................................................................... 8

Creek flow and water temperature ............................................................................................. 9

Redd temperature exposure..................................................................................................... 9

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Adult exposure ........................................................................................................................ 9

Discussion......................................................................................................................................10

Relationship between live fish, redds, and carcasses ............................................................... 10

Supplemental spawning gravel ................................................................................................. 11

Weir monitoring ........................................................................................................................ 12

Water temperature exposure of holding adults and redds ........................................................ 13

Water temperature and flow criteria ........................................................................................ 13

Acknowledgments ........................................................................................................................14

References ......................................................................................................................................15

Tables ............................................................................................................................................17

Figures ...........................................................................................................................................28

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List of Tables

TABLE 1.—Number of Clear Creek spring Chinook salmon snorkel surveys conducted per

reach, 1999-2007................................................................................................................... 18

TABLE 2.—Clear Creek snorkel survey observations in 2007 of live adult Chinook salmon,

carcasses, and redds. Survey conditions for each reach include stream flow, average

turbidity, and average water temperature. ............................................................................. 19


carcasses, and redds for each survey week. Survey conditions include average flow, water

temperature, and turbidity during each snorkel survey week. Live, carcasses and redd

columns are divided by reach and displayed as: Reaches 1-5a (Reach 5b) [Reach 6]. Reach

6 was not surveyed in October or November........................................................................ 20

TABLE 4.—Live adult spring Chinook salmon (SCS) counts during the June and August Index

snorkel surveys on Clear Creek from 1999-2007. The temporary weir was first installed in

2003. From 2003-2005, the weir was placed at the Reading Bar (RB) site. In 2006 and

2007, the weir site was located at the Shooting Gallery (SG) site. We determined the weir

site based on the percent of the SCS August Index count between the weir sites ................ 21

TABLE 5.—Spring Chinook salmon redds observed during Clear Creek snorkel surveys

upstream in Reaches 1-5b from 2003-2007. The temporary picket weir was first installed in

2003. Table includes percent of redds that contained injection gravel in Reaches 1-5a.

Reach 5b is located downstream of the weir and redds were classified as fall Chinook

salmon. .................................................................................................................................. 22

TABLE 6.—Distribution of Clear Creek spring Chinook salmon redds counted during snorkel

surveys upstream of the temporary picket weir. River miles (RM) begin at Whiskeytown

Dam and end at the picket weir location. River miles represent actual distance of the creek,

except for RM 11. From 2003 to 2005, the distance of RM 11 was 0.13 mile. In 2006 and

2007, the location of the picket weir was further downstream and RM 11 increased to 0.88

miles. ..................................................................................................................................... 22

TABLE 7.—2007 Clear Creek spring Chinook salmon redd characteristics, collected during

snorkel surveys in Reaches 1-5a. Average redd characteristics from 2003-2006 snorkel

surveys of Reaches 1-5a are presented for comparison. ....................................................... 23

TABLE 8.—Spring Chinook salmon carcass counted upstream of the temporary picket weir

during Clear Creek snorkel and weir surveys from 2003-2007. Also includes carcasses

recovered in downstream of the weir in Reach 5b. ............................................................... 24

TABLE 10.—Information on adipose-fin clipped Chinook salmon carcasses and coded-wire tags

(CWT) recovered on Clear Creek in 2007 during our snorkel surveys.a .............................. 25

TABLE 11.—Age structure of adult spring Chinook carcasses sampled in Clear Creek since

2003. Age determinations were made by reading scales from carcasses recovered in Reach

1-5a (upstream of the picket weir). Table includes total number of scales read (n=) and the

percent sampled of total carcasses counted in Reaches 1-5a. ............................................... 26

TABLE 12.—Clear Creek temporary picket weir installation dates and monitoring days from

2003-2007. Beginning in 2006, the location of the picket weir was either at Reading Bar

(RB) or at Shooting Gallery (SG), based upon the percent of SCS holding in the large pool

between the weir sites. .......................................................................................................... 26

TABLE 13.—Total redds per reach and the minimum percent of incubation time that spring

Chinook salmon eggs were exposed to temperatures >56oF in Clear Creek in 2005-2007. . 27

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List of Figures

FIGURE 1.—Map of study area, Clear Creek, Shasta County, California, 2007. ....................... 29

FIGURE 2.—Live adult Chinook salmon observed during 2007 Clear Creek snorkel surveys.

The temporary picket weir was located between Reaches 5a and 5b. We closed the picket

weir on August 23, following the Reach 5a snorkel survey, and removed it on November 1.

Reach 6 surveys ended on September 28 .............................................................................. 30

FIGURE 3.—Chinook salmon redds observed during 2007 Clear Creek snorkel surveys. The

temporary picket weir was located between Reaches 5a and 5b. We closed the picket weir

on August 23, following the Reach 5a snorkel survey, and removed it on November 1.

Reach 6 surveys ended on September 28. ............................................................................. 31

FIGURE 4.—Number of spring-run Chinook salmon redds observed during snorkel surveys of

Clear Creek in Reaches 1-5a from 2003-2007, and the proportion of these redds that

contained injection gravel. .................................................................................................... 32

FIGURE 5.—Spring-run Chinook (SCS) salmon redds that contained injection gravel, observed

during the Clear Creek snorkel surveys of Reaches 1-5a from 2003 to 2007. Each year

shows the number of redds that contained injection gravel and the number of redds

associated with the different gravel injection sites. The following sites did not have

injection gravel available for spawning until: Need Bridge site: 2004; Guardian Rock site:

2006; and Reading Bar site: 2006. The Reading Bar site gravel was actually first available

in 2003, however, it was downstream of the weir until 2006 and not available to SCS

upstream of the weir.............................................................................................................. 33

FIGURE 6.—Redd counts during the final September survey of Clear Creek in Reach 6 since

2001. Each year, we carried out surveys between September 23 and 29. ........................... 34

FIGURE 7.—Chinook salmon carcasses observed during 2007 Clear Creek snorkel surveys and

weir monitoring. The temporary picket weir was located between Reaches 5a and 5b. We

closed the picket weir on August 23, following the Reach 5a snorkel survey, and removed it

on November 1. Reach 6 surveys ended on September 28. ................................................. 35

FIGURE 8.—Chinook salmon carcasses retrieved during 2007 Clear Creek weir monitoring,

upstream of the weir. Weir monitoring occurred 3-5 days per week with no more than two

days between checks. ............................................................................................................ 36

FIGURE 9.—Box plots comparing the distribution of fork lengths for spring-run Chinook

salmon carcasses recovered upstream of the weir during weir monitoring and snorkel

surveys, from 2003-2007. Whiskers represent the 5th and 95th percentiles. ...................... 37

FIGURE 10.—Box plot representing fork length distribution from spring-run Chinook salmon

carcasses recovered during snorkel surveys and weir monitoring upstream of the weir in

2007. The median fork length from carcasses recovered on the weir was significantly

different from the carcasses recovered from the snorkel survey (n=25 for each survey).

Whiskers represent the 5th and 95th percentiles. .................................................................. 38

FIGURE 11.—Number of males, females, and unknown gender Chinook salmon carcasses

counted upstream of the Clear Creek picket weir during snorkel and weir surveys between

2003 and 2007. ...................................................................................................................... 39

FIGURE 12.—Percent of male, female, and unknown carcasses recovered during Clear Creek

snorkel surveys and weir monitoring from 2003-2007. ........................................................ 40

viii

FIGURE 13.—Age composition and fork length distribution of Chinook salmon carcasses

retrieved upstream of the weir during 2007 Clear Creek snorkel and picket weir monitoring

surveys in Reaches 1-5a. ....................................................................................................... 41

FIGURE 14.—Installation of the 2007 Clear Creek temporary picket weir monitoring site at

Shooting Gallery. .................................................................................................................. 42

FIGURE 15.—Mean daily water temperature (MDT) and mean daily flow (MDF) at the Igo

gage (RM 10.9) with temperature criteria for spring Chinook salmon (SCS) holding

(

RBFWO lower rotary screw trap (LRST) (river mile 1.7). .................................................. 43

FIGURE 16.—Mean daily water temperatures (MDTs) at select temperature monitoring sites in

period (June 1-September 14) at Igo. Bottom figure shows MDT during the spring Chinook

er temperature criteria period (September

15) at Igo begins.................................................................................................................... 44

FIGURE 17.—Relationship between the spring Chinook salmon August index, redd counts, and

carcass counts upstream of the weir on Clear Creek from 2003-2007. ................................ 45

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Introduction

The Red Bluff Fish and Wildlife Office (RBFWO) has monitored adult spring Chinook

salmon (SCS) (Oncorhynchus tshawytscha) in Clear Creek since 1999. The purpose of our

monitoring is to determine SCS population status in Clear Creek, evaluate the effectiveness of

restoration actions, and guide future restoration actions. The Clear Creek Restoration Program

has five major elements (DeStaso and Brown 2007), three of which directly target SCS, which

include increased creek flow (Brown 1996), addition of spawning gravel, which has been

blocked by Whiskeytown Dam (McBain and Trush 2001, GMA 2006), and the removal of

Saeltzer Dam in 2000 (DWR 1997, Hepler 2000).

Beginning in 1995, the U. S. Fish and Wildlife Service (USFWS) has requested that the

Bureau of Reclamation (BOR) increase water releases from Whiskeytown Dam to improve

salmonid holding, spawning, and rearing habitat and temperatures (Brown 1996). Gravel

supplementation projects have been implemented since 1996. The Western Shasta Resource

Conservation District (WSRCD) implements gravel addition projects on Clear Creek. Sites are

located from Whiskeytown Dam downstream to river mile 2.5 (Figure 1). Projects typically

consist of placing clean 1-4 inch gravel into the creek using an “injection method”. The injection

method involves trucking in clean gravel and dumping it over the steep canyon wall to form a

talus cone extending into the creek (WSRCD 2000). While some of the gravel enters into the

creek during this process, the majority remains in the talus cone and only becomes available for

spawning after high flows transport it downstream. The removal of Saeltzer Dam in the fall of

2000 increased the available anadromous salmonid habitat by 11.6 miles to the base of

Whiskeytown Dam.

After the removal of Saeltzer Dam, snorkel survey results showed there was not a

complete spatial or temporal separation between SCS and fall Chinook salmon (FCS) during

spawning (Newton and Brown 2004). Without separation, hybridization or redd superimposition

could occur and threaten efforts to restore SCS to Clear Creek. Since 2003, through consultation

with the National Marine Fisheries Service (NOAA Fisheries), we have installed a temporary

picket weir across Clear Creek to separate FCS from SCS during spawning.

Our monitoring consists of snorkel based surveys to count SCS adults, redds, and

carcasses, and the installation and monitoring of the temporary picket weir. This report

summarizes our 2007 monitoring results.

Study Area

Clear Creek is a west side tributary of the Sacramento River, located in Shasta County,

California (Figure 1). The BOR controls water releases into Clear Creek at Whiskeytown Dam,

which is located at river mile 18.1 and is a complete barrier to fish passage. Our study area

extends from Whiskeytown Dam downstream to the RBFWO lower rotary screw trap (LRST),

located at river mile 1.7. The elevation ranges from 1000 feet to 440 feet above sea level.

We divided the study area into seven reaches based upon distance, accessibility, and the

location of the temporary picket weir (Figure 1). The first two miles downstream of

Whiskeytown Dam are alluvial (Reach 1), and the substrate is a mixture of bedrock, cobble,

sand, and gravel. From river mile 16.1 (Need Camp Bridge) to 8.5 (Clear Creek Road Bridge)

(Reaches 2, 3 and 4), steep canyon walls confine the creek and consists of falls, high gradient

riffles, and deep pools. The substrate is mainly bedrock, large boulders, and sand. Downstream

2

from river mile 8.5 (Reaches 5a, 5b, and 6), the creek is alluvial and lower gradient, and the

substrate is a mixture of cobble, gravel, and sand. However, a steep cascade (Gorge Cascade) is

located at river mile 6.5, which divides Reaches 5b and 6, and is a partial barrier to FCS (Newton

and Brown 2004). The temporary picket weir divides reaches 5a and 5b from late August to

early November.

Clear Creek currently supports populations of SCS, FCS, and late-fall Chinook salmon

(LFC), as well as Central Valley steelhead (STT). The National Marine Fisheries Service

(NMFS) designated SCS as a threatened species in 1999 (Federal Register / Vol. 64, No. 179.).

Based upon our monitoring results, SCS begin to migrate into Clear Creek in April and spawning

begins in early September (Newton and Brown 2004, Newton and Brown 2005). Reaches 1

through 5a are the primary holding and spawning habitat for SCS and STT, while Reaches 5b

and 6 are the primary spawning habitat for FCS, LFC, and STT.

Following the installation of the temporary picket weir in 2003, the RBFWO installed a

rotary screw trap at river mile 8.4 to estimate fry and juvenile SCS outmigration. Based on our

juvenile outmigration trapping data, SCS salmon fry emerge begin in late November and peak

emigration occurs from mid December through mid January (Earley et al. 2008).

Methods

Our adult SCS monitoring consists of two methods (1) snorkel based surveys and (2) the

installation and maintenance of a temporary picket weir. Snorkel surveys consist of counting

and recording the location of adult SCS, carcasses, and redds. In addition, we take biological

samples from carcasses and collect redd characteristic data. During picket weir monitoring, we

ensure the weir remains fish tight and count and biologically sample carcasses.

Snorkel survey

Survey timing.—In 2007, snorkel surveys occurred in June and August, and every two

weeks from September through early November. From 2000-2005, we carried out snorkel

surveys monthly from April through August to determine migration timing, pre-spawn mortality

rates, temporal and spatial distribution of adult SCS, and if winter Chinook salmon were

spawning in Clear Creek (Newton and Brown 2004, Newton and Brown 2005). We decreased

the frequency of our surveys beginning in 2006 (Table 1) after we established that winter

Chinook salmon were not spawning in Clear Creek and we described the run timing and

distribution of SCS.

We chose to continue to survey in June because it gives an indication of the population

size and holding distribution and provides an opportunity to train and refresh field staff of

standard snorkeling and safety protocols. The August snorkel survey adult SCS count is our

annual population index. The timing of August survey provides the best estimate of the SCS

spawning population because flows are low and visibility is good, SCS are close to spawning,

and few FCS should have entered the creek. The California Department of Fish and Game

(CDFG) also use August snorkel surveys to obtain annual population indexes in other Central

Valley SCS watersheds, such as Deer and Butte Creeks. In early September, SCS spawning

begins on Clear Creek and we snorkel bimonthly through early November to count redds and

sample carcasses.

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In late September, adult FCS begin to move into Clear Creek in large numbers. We

terminate surveys in Reach 6 in late September when the number of FCS increases. In the

beginning of October, CDFG conducts carcass surveys to estimate the FCS escapement in Reach

6. We continue to conduct snorkel surveys in Reach 5b through November (identical to reaches

1 through 5a) to determine how many FCS are migrating and spawning upstream of the Gorge

Cascade.

Survey technique.—Surveys began at the upstream most reach (Reach 1) and continued

downstream on consecutive days. Each survey required a three-person snorkel crew and it took

three to five days to complete all six reaches. Three snorkelers moved downstream abreast (to

obtain complete coverage) with the current and counted Chinook salmon adults, carcasses, and

redds. Snorkelers divided the width of the creek into thirds and each snorkeler focused on

counting within their lane.

For the purpose of counting live adult SCS, when approaching large pools, one or two

snorkelers walked around and quietly entered the pool from downstream. After entering the

pool, snorkelers first looked for holding salmon in the bubble curtain, and then signaled the other

snorkeler to go through the rapid with the intention of flushing hiding salmon tucked up at the

head of the pool. Snorkelers normally counted salmon as they passed upstream, but if one

headed downstream, the crew would count it if it was not observed again. After snorkelers

observed salmon, they would confer at pool tails to discuss counts and ensure they did not miss

or double count salmon.

Environmental conditions.—Stream flow, water turbidity and water temperature can all

influence the effectiveness of snorkel surveys (Thurow 1994). Snorkel crews collected data on

these three parameters for each snorkel survey. Crews collected water samples at the beginning

and end of each survey, and then analyzed them for turbidity using a Hach Turbidimeter. Using

a hand held submersible thermometer, crews measured water temperature at the beginning and

end of each survey. For each survey, we obtained mean daily flows (MDF) from the U.S.

Geological Survey gaging station near Igo (Igo) (RM 10.9) (http://waterdata.usgs.gov).

Live.—During each snorkel survey, we recorded the number of live adult Chinook salmon

observed per reach and used a Garmin® Etrex GPS to document their locations. Our annual SCS

population index was the total salmon observed during the August snorkel survey in Reaches 1-

6.

Redds.—We counted and recorded the location of redds using a GPS. In order to

differentiate new redds counted on previous surveys, we also tied flagging to nearby vegetation

at the upstream end of the redd. Redds needed to have a clearly defined pit and tail-spill. Test

redds (areas of clean substrate that fish may have scratched, but do not contain both a pit and

tail) were not counted as redds. We marked these areas with a different color flag for the next

crew to check. Redd counts upstream of the temporary picket weir (Reaches 1-5a) were

considered our SCS redd annual redd count.

Redd characteristics.—Redd measurements consisted of area, depth, water

velocity, and substrate size. Redd dimensions included maximum length parallel to the

flow and maximum width perpendicular to the flow. Redd area was calculated using the

formula for an ellipse (area = π½ width½ length). Depth measurements included

maximum pit depth, minimum tailspill depth, and pre-redd depth, which was measured

immediately upstream of the redd. Mean column velocity was measured at the same

location as the pre-redd depth and taken with a General Oceanics model 2030 mechanical

4

flow meter or a Marsh-McBirney model 201 meter. We classified dominant substrate

size using methods described by USFWS (2005).

Gravel injection.—To evaluate the use of spawning habitat created by the gravel

supplementation projects, we noted when redds were constructed in injection gravel.

There are six gravel injection sites located Reaches 1-5a and they include Whiskeytown,

Need Camp Bridge, Guardian Rock, Placer Road Bridge, Clear Creek Road Bridge, and

Reading Bar (Figure 1). Each year, we tracked the distance injection gravel moved

downstream following the winter storm season (Figure 1). During our June snorkel

survey of Reaches 1-5a, we took a waypoint at the downstream extent of injection gravel.

Crews identified injection gravel in redds based on how far it moved downstream in the

creek, the presence of tracer rock (chert, not native to the watershed), and uniform size

(2-4") and shape (rounded edges).

Redd distribution.—Using GIS, we summarized redd densities per mile in

Reaches 1 through 5a. Beginning at Whiskeytown dam and moving downstream to the

weir site, we divided the creek into miles (river mile 1 through 11). River mile 11 was

not a complete mile and its distance varied depending on the location of the weir. From

2003 through 2005, it was 0.3 miles and in 2006 and 2007, it was 0.88 miles.

Carcasses.—During snorkel and weir surveys, we counted and biologically sampled

salmon carcasses. We designated carcasses collected upstream of the picket weir as SCS. For

each carcass, we recorded its location with a waypoint and marked it by removing its caudal fin

so crews would not count it on a subsequent survey. For carcasses that we could not retrieve, we

took as many notes as possible concerning the status of the carcass (sex, spawning condition,

adipose fin presence, etc.)

Crews collected biological data from each carcass including fork length, gender,

spawning status, presence of an adipose fin, and carcass condition. Crews collected heads from

adipose-fin clipped carcasses (and from carcasses when the presence of an adipose fin could not

be determined due to decomposition or predation) for coded-wire tag retrieval. Coded-wire tags

were extracted from heads in the laboratory. We collected quadruplicate tissue samples for

genetic analysis. Samples were usually collected from a fin but the operculum was sampled if

the fins were highly decayed or worn down. Three samples were placed in vials containing

ethanol and one was dried. Crews also collected scales and otoliths. All samples are archived at

the RBFWO. We used a Wilcoxon rank sum test to determine if fork lengths from carcasses

recovered on the weir were different from carcasses collected on snorkel surveys.

Age structure.—We collected and read scales to determine the age of SCS

carcasses recovered upstream of the temporary picket weir. Field crews collected 5 to 10

scales from the left side of a carcass from the second and third row of scales above the

lateral line, in the region bisected by a line drawn between posterior insertion of the

dorsal fin to the anterior insertion of the anal fin. Back at the office, crews dried scales

for 24 hours then stored them in scale envelopes until they were prepared for reading. To

prepare for reading, scales were hydrated and cleaned in soapy water, and then mounted

sculptured side up between two glass microscope slides held together with tape. Scale

readers used a microfiche reader to count the number of annuli and the age was

determined to be the number of annuli plus one (Borgerson 1998). Scale readers were

trained using FCS and LFCS of known age from Coleman National Fish Hatchery. Two

scale readers independently aged each scale. If results were incongruent, the scale was

5

read a third time cooperatively by the same two readers. If the scale readers did not reach

an agreement after the third read, the scale was not included in our data set.

Temporary picket weir installation and monitoring

Location and operation dates.—Since 2003, we have installed a temporary picket weir

across Clear Creek to separate FCS from SCS during spawning to prevent hybridization and redd

superimposition between the runs. During Clear Creek Technical team meetings, fishery

biologists from our office, CDFG, BOR, and NOAA Fisheries determined weir installation and

removal dates and site location after considering the timing of migration and spawning of SCS,

FCS, LFCS, and STT in Clear Creek.

We typically install the weir in late August and remove it in early November. The weir is

closed during the August Index snorkel survey, after Reaches 1-5a are snorkeled. The weir

operation period provides time for the majority of the SCS to spawn before allowing FCS access

to SCS spawning habitat. The weir installation date allows maximum time for SCS to migrate

upstream of the weir before FCS begin to migrate into Clear Creek, while the removal date

occurs prior to peak of the steelhead or LFCS migration and beginning of spawning.

We chose the weir location to maximize the number of SCS upstream of the weir without

affecting FCS spawning habitat availability. From 2003 through 2005, the weir site was located

at Reading Bar at river mile 8.1 (Figure 1). However, we moved the weir downstream to the

Shooting Gallery site at river mile 7.4 in 2006 and 2007 to isolate a higher percentage of the SCS

population upstream of the weir. We performed supplemental snorkel surveys in July and

August in 2007 to count holding salmon in the large pool between the weir sites. Based upon the

number of salmon counted, we determined our weir location.

Construction.—The weir was constructed of wooden frames set eight feet apart and

connected with aluminum channel beams into which are inserted six-foot-long ¾” aluminum

conduit, spaced 2c ” on center. The conduit extended to the stream bottom and gaps were filled

with native cobbles or sandbags. The weir was anchored to iron fence posts driven vertically

into the streambed. In 2007, we attached hose clamps to individual pieces of conduit to prevent

anyone from lifting pickets. For public safety, we posted signs in the creek to warn rafters and

swimmers of the location of the weir. We also posted informative signs along the shore to

inform the public of the purpose of the weir and to alert anglers of the regulation prohibiting

fishing within 250 feet of a weir.

Monitoring.—The weir was inspected 5 days per week, to be sure it was fish tight,

remove debris, detect vandalism, and sample Chinook salmon carcasses (as described under

snorkel methods). Crews searched for any gaps resulting from bent conduit, conduit not in

contact with the streambed, or breaches around the sides of the weir. Crews removed debris

from the upstream face of the weir, collected and quantified it in 10-gallon plastic tubs using

categories; low (<three tubs), moderate (three-six tubs), and high (>six tubs). If more than 20

live adult Chinook salmon are observed in Reach 5b during our late October snorkel survey, we

would have left the weir in until the middle of November to prevent negative impacts to SCS

redds. In addition, we monitored steelhead downstream of the weir by counting them during bi-

weekly snorkel surveys within 1000 feet downstream of the weir. If snorkel crews counted more

than ten adult STT greater than 22 inches, we would have temporarily removed pickets to allow

steelhead to pass upstream.

6

Creek flow and water temperature

We evaluated water temperatures based on the criteria established in the Anadromous

Fish Restoration Program Restoration Plan in 1995 (USFWS 2001) and the Biological Opinion

for the Central Valley Project and State Water Project operations (NMFS 2004) for SCS holding

and spawning. The BOR releases 200 cubic feet per second (cfs) from October 1 to June 1 from

Whiskeytown Dam to provide sufficient habitat and water temperatures for SCS, FCS, LFCS,

and STT egg incubation and rearing. Beginning on June 1, the BOR reduces flows and

maintains them at a level to keep mean daily water temperature (MDT) ≤ 60ºF at Igo. This flow

regime provides adequate conditions for adult SCS holding and juvenile salmonid rearing. In

mid September, the BOR increases flows from Whiskeytown reservoir to maintain MDT ≤56°F

at Igo for SCS spawning and egg incubation.

Redd temperature exposure.—To evaluate exposure of incubating eggs to high water

temperatures, we used MDT data and SCS redd observation dates. We have 11 water

temperature monitoring sites located throughout Clear Creek (Figure 1). We use Onset Hobo®

Water Temp Pro v2 or Optic StowAway®

temperature loggers, which are accurate to 0.36°F, and

calibrated before deployment in the field. At each site, we deploy two temperature loggers to

prevent loss of data due to lost or malfunctioning loggers.

In GIS, we calculated the river mile for each redd location. We interpolated MDT at redd

locations by using the equation of a straight line connecting two adjacent temperature monitoring

sites. We calculated the days of exposure ≤56°F based on the criteria that 1,850 Daily

Temperature Units (DTU= MDT minus 32°F) were required for egg incubation to time of

emergence (Piper et al. 1982). Minimum days of exposure were calculated using the day before

the redds were first observed and maximum days of exposure were calculated using the day after

the previous snorkel survey week (approximately 2 weeks earlier).

Results

Snorkel surveys

From June 11 through November 9, we conducted seven snorkel surveys in Reaches 1

through 5b, and three surveys in Reach 6 (Table 1 and Table 2). Viewing conditions during the

survey period were good; average MDF at Igo was 161 cfs, average turbidity was 1.0 ntu, and

average MDT was 56F (Table 3).

Live.—We observed 100 live adult SCS during our June snorkel survey and our SCS

August index count was 194 (Figure 2, Table 4). During the August snorkel survey, 94% of the

SCS were located upstream of the weir after it was closed (Figure 2, Table 4). Observations of

SCS upstream of the weir (Reaches 1-5a) declined for the remainder of the study period (Figure

2). Downstream of the weir, Chinook salmon observations slightly increased during the first

September survey week, indicating that FCS may have started to migrate into Clear Creek

(Figure 2). By the second September survey week, Chinook salmon counts increased to 17 in

Reach 5b, and 303 in Reach 6 (Figure 2).

Redds.—Upstream of the picket weir (Reaches 1-5a), the SCS redd count was 49 (Table

5). Nine redds were observed during the first September survey week (on September 11 and 12)

in Reaches 1-3 when MDF was 83 cfs (Figure 3). Redd counts peaked in Reaches 1-5a during

7

the second September survey week when MDF was 168 cfs (Figure 3). The highest density of

redds in Reaches 1-5a occurred in river miles one and three (11 redds in each mile) (Table 6).

Figure 1 displays the downstream extent of injection gravel for each site. Thirty-five

percent of redds contained injection gravel, compared to an average of 28% since 2003 (Figure

4). Redds were constructed in gravel from each injection site, except Reading Bar (Figure 5).

Average redd size was 109.5 ft2 (n=48), which is similar to average redd sizes from 2003 through

2006 (Table 7). Average pre-redd depth was 1.93 ft (n=47); average pre-redd water velocity was

2.3 ft/s (n=47); and median substrate size was 1 to 2 inches (n=47).

Downstream of the weir, we observed 35 redds in Reach 5b (Table 5). Redds were first

observed during the second September survey week and counts peaked during the first October

survey week (Figure 3). No redds were observed in Reach 6 until the final snorkel survey on

September 28, and we counted 99 redds (Figure 3). Figure 6 shows redd counts during the late

September Reach 6 survey since 2001.

Carcasses.—The SCS carcass count (Reaches 1-5a) was 72 (Table 8). In addition, we

counted five carcasses in Reach 5b during snorkel surveys.

Snorkel carcass recovery.—We recovered 42 SCS carcasses during snorkel

surveys (Figure 7). Four pre-spawned carcasses were recovered during June and August

snorkel surveys and we included one additional carcass that was found in Reach 4 in May

during a supplemental survey in Clear Creek. All five carcasses had signs of predation,

but we could not determine the cause of death. Two of the carcasses were mostly intact

(one male and one female) and they both had adipose fins, however, spawning status was

unknown because their intestines were missing. The other three carcasses were

fragments and we could not determine their sex, spawning status, or length. Carcasses

recovered in May and June were most likely pre-spawning SCS mortalities, but it is

possible that they were winter Chinook salmon. However, snorkel crews did not observe

redds on the June survey, indicating that these fish did not spawn.

While the weir was in, snorkel crews counted 37 carcasses upstream of the weir.

We counted one carcass during a temperature monitoring survey on Reach 2 and added

this to the total. Four of the 37 carcasses were too deep to retrieve or too decomposed to

mark, therefore, based on the dates of observation, crews may have re-counted two of

these carcasses on a subsequent survey. In addition, two of the carcasses were upstream

of the weir site during the November snorkel survey after it we removed it. Peak SCS

carcass recovery occurred during the first October snorkel survey week (Figure 7).

Weir carcass recovery.—Thirty carcasses were retrieved upstream of the weir and

two carcasses were retrieved downstream of the weir during weir monitoring (Table 9).

Carcass recovery on the weir peaked between September 26 and October 10 (Figure 8).

Bio-sampling.—Median fork length of carcasses collected during snorkel surveys

and weir monitoring upstream of the weir was 583 mm (n=50) (Figure 9). Based on

gender, median fork length of males was 503 mm (n=28), females was 750 mm (n=16),

and unknown gender was 558 (n=6). Median fork length was significantly different

between carcasses recovered on the weir compared to those recovered during snorkel

surveys (p = <0.001) (Figure 10).

Of the carcasses with known genders (n=53), the male to female sex ratio was

2.1:1 (68% male) (Table 8). Twenty-six percent of carcasses had an unknown gender due

to decomposition or predation, and this percentage is similar to other years (Table 8).

Most carcasses recovered on the weir were males (87%) while most carcasses recovered

8

during snorkel surveys were females (38%) and unknown gender (38%), which is similar

to previous years (Figure 11 and Figure 12). The first carcass recovered on the weir on

September 15 was an un-spawned female. We identified all other female carcasses

collected during the spawning season as spawned.

Two carcasses had known adipose fin clips. After processing the heads back at

the laboratory, we detected a coded wire tag in one of the two heads. The second head

was very decayed and it is possible the tag was lost. The coded wire tag recovered was a

Feather River Hatchery SCS, brood year 2004 (Table 10). Nine of the recovered

carcasses had unknown adipose fin clips. We processed five heads in the laboratory and

did not detect coded wire tags (Table 10). The other four carcasses were unknown

adipose fin clip status because they were not retrievable in the field.

Age structure.—We read 54 scale samples from SCS carcasses upstream of the

weir (Table 11). Based on scale reading results, we estimated the age structure of SCS

spawning population ranged from age 2-4. The dominant age class was three-year-olds

(brood year 2004), comprising 67% of the sample (Table 11). The median fork length of

2-year-olds was 490 mm (n=15) and the median fork length of 3-year-olds was 680 mm

(n= 31) (Figure 13). Based on age and gender, 100% of females were age 3 (n=15); 44%

of males were age 2 (n=14); 53 % of the males were age 3 (n=17); and 3% of males were

age 4 (n=1). Of the unknown sex, 43% (n=3) were age 2 and 57% (n=4) were age 3.

Temporary picket weir installation and monitoring

On August 22, we installed the picket weir at the Shooting Gallery site and closed it on

August 23, following the Reach 5a snorkel survey (Figure 14). Based on the August snorkel

survey, 94% of SCS August Index was isolated upstream of the weir after it was closed. We

installed the weir at the Shooting Gallery site because we counted 22 SCS holding in the pool

between the weir sites, during the supplemental snorkel survey on August 16. By installing the

weir at the Shooting Gallery site and not the Reading Bar site, an additional 10% of the August

Index was protected upstream of the picket weir.

During the October 25 snorkel survey of Reach 5b, less than 20 (seven) live adult FCS

were observed, so we removed the picket weir on November 1. We did not count more than one

adult STT within 100 feet downstream of the weir during any snorkel survey of Reach 5b;

therefore, we did not need to lift pickets to allow passage.

We monitored the weir a total 44 of the 71 days that it was in the creek (Table 12).

Monitoring and cleaning occurred three to five times per week without going more than two full

days between visits. During most of the time the weir was in, debris was low to moderate.

Debris loads increased to high on several occasions towards the end of October due to storms

and fallen leaves. There was no evidence of tampering or lifted pickets and the weir remained

fish tight for most of the operation period. However, on October 26, a small storm event caused

the flows to rise slightly and 40 tubs of debris built up on the weir. Gravel scoured beneath the

weir due to debris accumulation, which allowed fish passage for a maximum of 18 hours before

the weir was adjusted. We retrieved one carcass on the weir on October 31, which may have

been a FCS that passed upstream on October 26 (Figure 8). Following the removal of the weir,

snorkel crews counted two live adult Chinook salmon, two redds, and two carcasses during the

November snorkel survey upstream of the weir site (Table 2).

9

Creek flow and water temperature

Flow and temperature targets were generally met during the study period (Figure 15).

Mean daily flows gradually declined beginning on June 1. Flows fluctuated at Igo between July

20 and September 13, ranging from 71 to 91 cfs (average 80 cfs). Flow increases began on

September 14 and transitioned to 120 cfs by September 15, 168 cfs by September 20, and 211 cfs

by October 3 (Figure 15).

During the ≤60F water temperature criteria period (June 1-September 14), MDTs at Igo

only slightly exceeded 60F on August 22 (0.3 F) during the 106 day criteria period. Average

MDTs from June 1 to September 14 was 57.0F (range 52.0-60.3F). When the water

temperature criteria decreased to ≤56F at Igo on September 15, MDTs exceeded 56F on 4

days, ranging from 56.1-56.7 F (average 56.4F) from September 15-18 (Figure 15).

Redd temperature exposure.—Figure 16 shows MDTs from several of our temperature

monitoring sites during the holding and spawning period. Table 13 shows the minimum percent

of days that redds upstream of the weir were exposed to MDTs >56F. None of the redds

upstream of the weir were exposed temperatures >56F after the date snorkel crews first

observed them. However, the number of days that a redd was exposed to high temperatures

depended on when the redd was constructed and when eggs were deposited, which was unknown

up until the date of the previous survey.

Nine redds were observed on September 11 and 12, before the temperature criteria of

≤56F at Igo took effect on September 15 (Reach 1=4 redds; Reach 2=4 redds; Reach 3=1 redd).

The redd in Reach 3 was not exposed to MDTs >56F after it was first observed but MDTs at the

redd location ranged from 56.6-58.2F (average 57.3F) during the two week period prior to

September 12. After the temperature criteria took effect on September 15, five redds in Reach 4

and Reach 5a were exposed to MDTs >56F (maximum 58.1F) between zero and eight days,

depending on when eggs were deposited.

In addition, Chinook salmon redds in Reach 5b and Reach 6 may have been exposed to

MDTs slightly >56F (Figure 16). The first redds were observed on September 27 in Reach 5b

and on September 28 in Reach 6, and MDTs were ≤56F by October 4. Between September 15

(day after previous survey) and October 4, MDTs ranged from 54.7-59.2F (average 56.6F) at

the top of Reach 6 and exceeded 56F on 15 days. At the end of Reach 6, MDT exceeded 56F

on 17 days during this same time and MDTs ranged from 55.2-61.4F (average 57.8F) (Figure

16).

Adult exposure.—Adult SCS upstream of Igo were only exposed to temperatures greater

than 60F for one day (60.3°F). During the June snorkel survey, 59% (59 adults), and the during

the August snorkel survey, 44 % (86 adults) of the SCS were holding downstream of Igo

(Reaches 4-6). At the end of Reach 4, MDTs were >60°F from July 9 through September 6 for

43 days (maximum 62.6°F, average 60.4°F). At the end of Reach 5b, MDTs were >60°F from

July 4 to September 12 for 68 days (maximum 64.9°F, average 62.6°F). Near the location of the

most downstream salmon observed in Reach 6, MDTs were >60°F from July 2 to September 13

every day (maximum 66.6F, average 63.8°F) (Figure 16).

10

Discussion

Based upon our monitoring results, restoration actions on Clear Creek have been

successful at increasing spawning habitat and providing water temperatures and flows for all life

stages of SCS, including adult passage, holding, egg incubation, and rearing. The picket weir

separated FCS from SCS during spawning and we are seeing increasing returns from brood years

when the weir was in.

Our snorkel survey is a useful technique for monitoring adult SCS in Clear Creek because

we cover the entire SCS habitat, visibility is excellent, and we conduct frequent surveys. The

timing of our snorkel surveys is appropriate for collecting data concerning adult SCS. The

August snorkel survey is a good index of the SCS spawning population because it is conducted

when flows and turbidities are low, which makes visibility excellent for counting fish; the SCS

are close to spawning so pre-spawning mortalities have already been accounted for; and FCS

have not yet entered the creek in significant numbers. We survey more frequently during the

spawning period (every two weeks) so redds are not missed due to age. Algae growth and flows

age redds and make them less visible to snorkel crews. Carcasses decompose quickly and are

scavenged by predators, so more frequent surveys are necessary for carcasses recovery.

This year was the highest SCS August index recorded since 1999, which suggests the

Clear Creek population is beginning to establish. Age structure indicated that 67% of SCS

upstream of the weir were age 3, and 31% were age 2, suggesting that the 2007 SCS population

resulted from successful returns from Clear Creek brood years 2004 (August Index = 98) and

2005 (August Index = 69). Based upon the coded-wire-tag recoveries, Feather River Hatchery

SCS are also contributing to the Clear Creek population. In 2004, a wild Butte Creek fish coded

wire tag was recovered in Clear Creek, which suggests that strays from the other two remaining

independent populations of SCS from Mill and Deer creeks may also be contributing to the

recovery of SCS in Clear Creek. We recommend having our tissue samples run to verify the

genetics of the Chinook salmon returning to Clear Creek to gain a better understanding of the

origins of the spawning population.

Relationship between live fish, redds, and carcasses

We do not fully understand the relationship between the August index, redd counts, and

carcasses recovered upstream of the picket weir (Figure 17). When comparing data from 2003-

2007, the strongest relationship that exists between these variables is between female carcasses

and redds (r2=0.847).

In 2007, the proportion of redds to the August index was much lower when compared to

other years. Variations in yearly sex ratios may change the relationship between the August

index and redd counts. This year, there were more males than females (2.1:1 ratio), which may

explain why there were fewer redds than expected if the August index had a one to one male to

female ratio. If we apply the sex ratio to the August index count upstream of the weir, there

would have been approximately 58 females, which would be more comparable to the number of

redds (n=49).

Since sex ratios are based on carcass data, biases in different carcass recovery methods

may skew sex ratios. The picket weir has been an effective method for capturing carcasses; an

average of 45% of our SCS carcasses have been collected on the weir since 2003. The weir

captures more males than females (Figure 12). Males are more likely to be captured on the weir

11

due to their behavior during spawning; they spawn with multiple females and may travel

throughout the spawning grounds seeking new females. Since the percentage of carcasses

recovered on the weir can vary yearly (31-65% since 2003), the number of males may be over or

under represented each year. However, the percentage of carcasses captured on the weir may be

a result of the number of males in the spawning population. On snorkel surveys, we generally

recover more females and unknown genders than males. Female carcasses are more frequently

captured on the spawning grounds because they build one redd and guard it until death. Because

we conduct snorkel surveys less frequently than weir monitoring, we recover more unknowns on

snorkel surveys because they are older and more decomposed.

Using carcass data from both the weir and the snorkel survey may better characterize the

spawning population than if only a single carcass recovery technique was used. The weir

captures a high proportion of SCS carcasses that snorkel crews would not otherwise have

recovered. This year, our carcass recovery data showed that there was a high proportion of

males in the spawning population, which would explain why there were fewer redds than

expected.

Carcass size may also influence carcass recovery on snorkel surveys. Zhou (2002)

suggested that salmon carcass surveys underestimate smaller carcasses because they are more

difficult for observers to detect, more likely to be taken by scavengers, and more easily wash

downstream. This year, we found that carcasses captured on the weir were significantly smaller

than carcasses collected on snorkel surveys and were mostly males (Figure 10). However, fork

length data from previous years does not show that carcasses captured on the weir were smaller

than those recovered during snorkel surveys. There was a high percentage of jacks in the

spawning population in 2007. Snorkel crews also noted the high percentage of jacks during the

June and August snorkel surveys.

Our August snorkel survey index may detect an inconsistent proportion of the actual

population, which may account for the yearly variability between the August index, redd counts,

and carcass counts. Shardlow 1987 showed that snorkel survey counts underestimated live

salmon counts when compared to known counts. Although this would not explain results from

this 2004 or 2007, redd counts were high compared to the August index in 2003, 2005, and 2006,

regardless of the sex ratio. However, in years when the weir was not fish tight due to damage or

tampering (2004 and 2006), redd count and carcass recoveries may have been higher than

expected due to FCS passing upstream of the weir.

Supplemental spawning gravel

Gravel addition projects have successfully created habitat suitable for SCS spawning as

evidenced by the number of redds directly observed in injection gravel or in injection gravel

integrated into native gravel. Since 2003, an average of 28% of the total redds upstream of the

picket weir have contained injection gravel. In most locations, gravel created spawning habitat

that did not exist or had limited use prior. While the majority of the tons of supplemental

spawning gravel are delivered to Clear Creek at long-term sites using the “injection method”,

smaller gravel projects may also be beneficial for creating spawning habitat. During the

construction of the new Need Camp Bridge in 2004, a small amount of spawning gravel was

placed at this site. Chinook salmon spawned in the gravel after it moved downstream and

incorporated into the native gravel.

12

The use of spawning sites that contain injection gravel varies yearly, perhaps due to

fluctuations in the amount of gravel at each site. Spawning habitat changes as new gravel is

added and high flows moves the gravel downstream. This is especially true immediately

downstream of an injection site. For example, the percentage of redds in the Placer injection

gravel declined this year, and snorkel crews noticed that the habitat used in 2006 was not as

suitable (shallower and swifter). This was probably due to the newer gravel that was added in

2005, which moved downstream following high flows. However, as high flows continue to

move gravel downstream, spawning habitat will continue to improve further downstream and

likely increase over time.

Long term spawning gravel supplementation is important for improving and creating

spawning habitat on Clear Creek. We recommend continuing to supplement spawning gravel at

the existing sites, and incorporating new gravel sites including method-types such as injection,

in-stream placement, and lateral berms.

Weir monitoring

Based on our monitoring since 2003, the temporary picket weir has successfully

prevented redd superimposition by FCS and reduced the potential for hybridization between SCS

and FCS. We have observed that 95% of SCS spawning occurs by the end of September, while

peak spawning occurs in Reach 5b in early October. While there is some temporal separation of

spawning between Chinook salmon upstream of the weir and in 5b, there would probably be

hybridization without the weir in place.

In 2007, the weir remained fish tight until a storm event in late October. However, this

breach did not impact the SCS because spawning was complete and there were few FCS in

Reach 5b. During our snorkel survey after the weir was removed, we did not observe

superimposed redds and based on their age, the two new redds that were observed the November

survey were probably SCS redds missed during earlier surveys.

Newton and Brown 2005 first showed that the weir installation date was appropriate to

prevent FCS from passing upstream of the weir site, while allowing adequate time for SCS to

migrate upstream of the weir. Previous monitoring also showed that we removed the picket weir

at the appropriate time when few FCS are in Reach 5b (Newton and Brown 2005). Although

FCS continue to spawn into December in Reach 6, very few were present in Reach 5b after

November 1. However, in 2005, we extended the time the weir was in the creek for two weeks

due to the high number of FCS in Reach 5b. This was the first year that hundreds of FCS

remained in Reach 5b through November 1. Even at the time of removal, there were 92 FCS in

Reach 5b immediately prior to the removal of the weir.

Since 2005, we considered the number of FCS downstream of the weir before removing

it on November 1. We also surveyed the upper reaches after the weir removal to look for any

FCS spawning. This year, based on the low number of FCS in 5b, removing the weir on

November 1 was appropriate for protecting SCS redds upstream of the weir.

Moving the weir location downstream to the Shooting Gallery site isolated a greater

number of SCS upstream of the weir in 2007, which helped protect a greater proportion of the

Clear Creek SCS population. Although moving the weir downstream caused some loss of FCS

spawning habitat, the loss was minimal. We estimate that less than 2% of the FCS population

migrates upstream of the Gorge Cascade, and there is an adequate amount of spawning habitat

upstream to the weir for those that do.

13

We were hesitant to move the weir to the Shooting Gallery site this year because we had

problems with people lifting pickets in 2006, which may have occurred because of the easier

public access at the site. The lifted pickets probably allowed FCS to migrate upstream of the

weir and while we did not observe any redd superimposition in 2006, there was a chance that

some FCS hybridized with SCS. Although the weir was only partially effective at blocking FCS,

based upon the timing of lifted pickets, we believe the impact to SCS was minimal. In

2007, we used hose clamps to lock down the pickets to prevent people from lifting them, and

signs to warn and inform visitors of the importance of the picket weir. These techniques

appeared to prevent tampering and we will continue to use them in the future. We will also

consider moving the weir to the Reading Bar site if salmon are not present in the pool between

the sites during our August snorkel survey.

Water temperature exposure of holding adults and redds

Upstream of the weir, negative impacts to SCS eggs appear negligible, as MDTs were

elevated for only a short duration for six redds (range of 0-15 days) and were always <58.2°F.

For holding SCS, MDTs remained below 60°F at Igo throughout the summer (except for one

day) but 44% of the population was holding downstream of the temperature target location in

August. In Reaches 4, 5a, and 5b, there are no barriers to prevent SCS from migrating upstream.

Although the Gorge Cascade is a partial barrier to FCS, it is not likely the SCS in Reach 6 were

blocked, but prefer the habitat in a large, deep pool, similar to the one located between the weir

sites in Reach 5a. It is also possible that the SCS do not hold in these pools all summer but move

upstream and newly migrating SCS reoccupy the pool. Although water temperatures were

>60°F for some of the holding period downstream of Igo, average MDTs ranged from 60.4°F to

63.8°F when water temperatures were warmest. In the future, we may evaluate moving the

temperature criteria site at Igo downstream to increase the proportion of SCS protected.

Water temperature and flow criteria

From 1999-2004, flows from 68-94 cfs were required to meet the 60°F criteria for SCS

adult holding and juvenile rearing and >150 cfs to meet the 56 °F criteria in September

(Newton and Brown 2004, Newton and Brown 2005). In 2006 and 2007, similar flow regimes

were required to meet temperature criteria. However, in 2005, the 56°F was not met

consistently until November 17 and MDT ranged from 54.3°F to 58.0°F (mean 56.6°F). To meet

the 60°F criteria, flows from 116-160 cfs were required (average of 136 cfs). In 2005, water

exports from the Trinity River were reduced to provide more water in the Trinity River and the

timing of deliveries was changed. The timing of deliveries produced undesirably higher water

temperatures in both Clear Creek and the Trinity River because when no water was exported to

Whiskeytown, both Whiskeytown and Lewiston Reservoir on the Trinity River warmed up. If

future water exports from the Trinity River into Whiskeytown reservoir change creating warmer

water in the reservoir, flow releases into Clear Creek may need to increase to meet temperature

criteria for Chinook salmon.

14

Acknowledgments

We gratefully acknowledge the hard work and dedication of our snorkel survey crew leaders,

David Colby and Laurie Stafford and our field crew: Tara Anderson, Tim Blubaugh, R.J.

Bottaro, Jacob Cunha, Jessica Fischer, Jacie Knight, David LaPlante, Hayley Potter, and Andy

Trent. Thank you to Jess Newton for laying the foundation for the Clear Creek adult SCS

monitoring reports. We thank the Whiskeytown National Recreation Area and the Bureau of

Land Management for providing creek access on public lands. The CALFED Ecosystem

Restoration Program provided California Department of Water Resources funding for this

project from Proposition 50, under grant number P0685508, which was administered by the

California Department of Fish and Game and GCAP Services, Costa Mesa, California

(Sacramento Office).

15

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16

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Improvement Act. Released as a revised draft on May 30, 1997 and adopted as final on

January 9, 2001.

USFWS (U.S. Fish and Wildlife Service). 2005. Monitoring of restoration projects in Clear

Creek using 2-dimensional modeling methodology. Prepared by The Energy Planning

and Instream Flow Branch, Sacramento Fish and Wildlife Office, California.

Western Shasta Resource Conservation District. 2000. Lower Clear Creek spawning gravel

restoration projects 1997-2000. Prepared for Bureau of Reclamation, September 2000.

Zhou, S. 2002. Size-dependent recovery of Chinook salmon in carcass surveys. Transactions

of the American Fisheries Society. 131:1194-1202.

17

Tables

18

TABLE 1.—Number of Clear Creek spring Chinook salmon snorkel surveys conducted per

reach, 1999-2007.

Year Reach 1 Reach 2 Reach 3 Reach 4 Reach 5a Reach 6

1999

1

1

1

3

4

22

2000

7

6

7

8

8

12

2001

8

8

8

8

8

10

2002

11

10

10

10

10

7

2003

12

10

10

9

9

7

2004

12

12

12

12

12

8

2005 11 11 11 11 11 7

2006 6 6 6 6 8 3

2007 7 7 7 7 9 4

a Reach 5 was divided into 5a and 5b beginning in 2003, following the installation of the temporary picket weir.

19


carcasses, and redds. Survey conditions for each reach include stream flow, average turbidity,

and average water temperature.

Reach Date Livea Carcasses Redds

Temperature

(°F)

Turbidity

(NTU)

Flow

(cfs) 1 6/11/2007 2 1 0 52.0 0.6 169

1 8/20/2007 21 1 0 57.3 0.6 71

1 9/11/2007 5 1 4 57.5 0.6 83

1 9/24/2007 23 0 5 54.5 0.8 168

1 10/10/2007 1 3 8 55.0 1.1 216

1 10/22/2007 0 2 0 54.5 1.0 212

1 11/5/2007 1 0 1 52.5 1.3 209

2 6/11/2007 11 0 0 54.0 0.6 169

2 8/20/2007 70 1 0 55.0 0.7 71

2 9/11/2007 60 1 4 56.0 0.9 83

2 9/24/2007 19 1 10 56.5 1.0 168

2 10/10/2007 0 6b 0 53.5 1.3 216

2 10/22/2007 0 2 2 55.0 1.6 212

2 11/07/2007 0 0 1 53.5 0.6 209

3 6/12/2007 28 0 0 53.5 1.7 167

3 8/21/2007 17 0 0 55.0 1.0 71

3 9/12/2007 10 1 1 57.0 1.8 83

3 9/26/2007 5 1 1 57.5 1.4 168

3 10/11/2007 0 2 0 54.5 1.3 215

3 10/23/2007 0 1 0 54.5 1.3 212

3 11/08/2007 0 2 0 53.5 1.2 209

4 6/13/2007 20 1c 0 56.5 0.5 166

4 8/23/2007 53 1 0 62.5 0.7 71

4 9/13/2007 24 0 0 57.8 0.9 83

4 9/27/2007 31 2 4 55.0 0.9 168

4 10/11/2007 0 5 3 53.0 0.9 215

4 10/24/2007 0 1 0 54.0 1.0 209

4 11/08/2007 0 0 0 52.0 1.0 209

5a 6/13/2007 13 0 0 56.5 0.5 166

5ad 7/25/2007 4 0 0 61.5 1.2 93

5ad 8/16/2007 22 0 0 63.0 0.6 71

5a 8/23/2007 21 0 0 62.5 0.7 71

5a 9/14/2007 9 0 0 57.5 0.9 83

5a 9/27/2007 4 2 4 57.0 1.0 168

5a 10/12/2007 0 2 1 57.5 1.4 217

5a 10/25/2007 0 2 0 55.5 0.6 209

5a 11/09/2007 1 0 0 53.5 1.0 209

5b 6/13/2007 3 0 0 56.5 0.5 166

5bd 7/25/2007 4 0 0 61.5 1.2 93

5bd 8/16/2007 2 0 0 63.0 0.6 71

5b 8/23/2007 3 0 0 62.5 0.7 71

5b 9/14/2007 5 0 0 57.5 0.9 83

5b 9/27/2007 17 0 7 57.0 1.0 168

5b 10/12/2007 24 2 20 57.5 1.4 217

5b 10/25/2007 7 2 7 55.5 0.6 209

5b 11/09/2007 0 1 1 53.5 1.0 209

6 6/14/2007 23 0 0 60.5 0.9 167

6 8/24/2007 9 0 0 67.5 0.7 79

6 9/14/2007 25 0 0 61.0 1.1 103

6 9/28/2007 303 8 99 58.0 2.3 168 a Counts may include repeat observations of the same individual live on subsequent surveys.

b One carcass was retrieved during a temperature monitoring survey in Reach 2.

c One carcass was retrieved in mid-May during a kayak survey of Reach 4.

d We conducted additional surveys in Reach 5a and 5b to determine if Chinook salmon were holding in the pool

between the Reading Bar and Shooting Gallery picket weir sites.

20

TABLE 3.—Clear Creek snorkel survey observations in 2007 of live adult Chinook salmon, carcasses, and redds for each survey

week. Survey conditions include average flow, water temperature, and turbidity during each snorkel survey week. Live, carcasses

and redd columns are divided by reach and displayed as: Reaches 1-5a (Reach 5b) [Reach 6]. Reach 6 was not surveyed in October

or November.

Survey Week Live Carcasses Redds Flow

(cfs)

Water

Temperature (F)

Turbidity

(NTU)

June Survey a 73 (3) [23] 2 (0) [0] 0 167 55.3 0.9

August Index Survey 182 (3) [9] 3 (0) [0] 0 72 59.5 0.7

1st September Survey 109 (5) [25] 3 (0) [0] 9 (0) [0] 86 57.8 1.0

2nd September Survey 82 (17) [303] 7 (0) [8] 24 (7) [99] 168 56.2 1.0

1st October Survey b 1 (24) 17 (2) 12 (20) 216 54.6 1.2

2nd October Survey 0 (7) 8 (2) 2 (7) 210 54.7 1.1

November Survey 2 (0) 2 (1) 2 (1) 209 53.0 1.0

a One carcass was retrieved in mid-May during a kayak survey of Reach 4.

b One carcass was retrieved during a temperature monitoring survey in Reach 2.

21

TABLE 4.—Live adult spring Chinook salmon (SCS) counts during the June and August Index snorkel surveys on Clear Creek from

1999-2007. The temporary weir was first installed in 2003. From 2003-2005, the weir was placed at the Reading Bar (RB) site. In

2006 and 2007, the weir site was located at the Shooting Gallery (SG) site. We determined the weir site based on the percent of the

SCS August Index count between the weir sites.

Survey Year June Survey August Index

Survey

Percent upstream of

weir

Percent

between weir sites

Percent

downstream of

Shooting Gallery

weir site

1999 6 35 0% 100%

2000 16 9 0% 0%

2001 2 0 0% 0%

2002 51 66 0% 30%

2003 28 25 72% 0% 28%

2004 111 98 69% 14% 16%

2005 59 69 86% 12% 3%

2006 67 77 99% 12% 1%

2007 100 194 94% 10% 6%

22

TABLE 5.—Spring Chinook salmon redds observed during Clear Creek snorkel surveys upstream in Reaches 1-5b from 2003-2007.

The temporary picket weir was first installed in 2003. Table includes percent of redds that contained injection gravel in Reaches 1-5a.

Reach 5b is located downstream of the weir and redds were classified as fall Chinook salmon.

Year Reach 1 Reach 2 Reach 3 Reach 4 Reach 5a

Total

Reaches

1-5a

% injection

gravel

Reach 5b

2003 11 19 5 16 2 53 15% 19

2004 6 9 3 14 5 37 32% 27

2005 16 15 4 14 3 52 35% 123

2006 11 16 20 22 13 82 32% 30

2007 18 17 2 7 5 49 35% 35

TABLE 6.—Distribution of Clear Creek spring Chinook salmon redds counted during snorkel surveys upstream of the temporary

picket weir. River miles (RM) begin at Whiskeytown Dam and end at the picket weir location. River miles represent actual distance

of the creek, except for RM 11. From 2003 to 2005, the distance of RM 11 was 0.13 mile. In 2006 and 2007, the location of the

picket weir was further downstream and RM 11 increased to 0.88 miles.

YEAR RM 1 RM 2 RM 3 RM 4 RM 5 RM 6 RM 7 RM 8 RM 9 RM 10 RM 11 total Redds per

mile

2003 6 4 4 12 4 3 0 11 3 5 1 53 5.2

2004 2 4 3 3 3 1 2 9 1 8 1 37 3.7

2005 10 6 6 5 4 0 4 9 4 3 1 52 5.1

2006 2 9 8 5 3 7 10 15 6 5 12 82 7.5

2007 11 6 11 6 0 3 0 5 0 5 2 49 4.5

23

TABLE 7.—2007 Clear Creek spring Chinook salmon redd characteristics, collected during snorkel surveys in Reaches 1-5a.

Average redd characteristics from 2003-2006 snorkel surveys of Reaches 1-5a are presented for comparison.

2007

Max Length

(ft)

Max Width

(ft) Area (sq ft)

Pre-redd

Depth (ft) Pit Depth (ft)

Tail-spill

Depth (ft) Velocity (ft/s)

Substrate

(in)

Mean 16.38 7.85 109.54 1.93 2.43 1.52 2.33 -

Median 15.75 7.54 92.64 1.71 2.17 1.33 2.33 2-3

Standard

Deviation 6.01 2.84 71.87 0.85 0.88 0.87 0.90 -

Count 48 48 48 47 47 47 47 47

Average from 2003-2006

Mean 14.59 7.49 93.17 2.35 2.64 1.66 2.21 -

Median 14.67 6.92 77.36 2.00 2.27 1.33 2.18 2-3

Standard

Deviation 5.61 3.32 73.28 1.15 1.04 0.99 0.80 -

Count 205 204 204 211 206 205 205 209

24

TABLE 8.—Spring Chinook salmon carcass counted upstream of the temporary picket weir during Clear Creek snorkel and weir

surveys from 2003-2007. Also includes carcasses recovered in downstream of the weir in Reach 5b.

Year Carcasses 1-5a

Snorkel and Weir

% carcasses

on weir

Male to

female ratio

% unknown

carcasses Carcasses in 5b

2003 25 32% 0.6 28% 23

2004a 45 67% 3.3 33% 21

2005 67 54% 1.9 16% 321

2006 62 31% 0.6 21% 3

2007 72 42% 2.1 26% 7 a Removed 19 carcasses recovered on the weir due to weir collapse; all carcasses were males.

TABLE 9.—Bio-sampling summary of spring Chinook salmon carcass recovered upstream of the temporary picket weir during Clear

Creek snorkel and weir surveys in 2007.

Weir Snorkel Totals

Total 30 42 72

pre-spawn mortalities 1a 5 6

genetic samples 29 36 65

readable scales 28 26 54

otoliths samples 27 27 54

adipose clip 1 1 2

unknown clip 1 14 15

adipose present 28 27 55 a One un-spawned female was recovered on the weir on September 15.

25

TABLE 10.—Information on adipose-fin clipped Chinook salmon carcasses and coded-wire tags (CWT) recovered on Clear Creek in

2007 during our snorkel surveys.a

Date Species Method

Fork

Length

(mm)

Adipose

Fin

CWT

Code b

Reach Run

Brood

Year Release

Release

Location Hatchery

8/20/2007 Chinook Snorkel

Survey 0 Unknown NTD

R2


Survey 0 Unknown NTD R3



10/5/2007c Chinook

Snorkel

Survey 0 Absent 062409 R6 Spring 2003 CDWR

San Pablo

Bay

Feather

River

10/5/2007c Chinook

Snorkel

Survey 0 Absent 062402 R6 Fall 2003 CDWR

San Pablo

Bay

Feather

River

10/7/2007 Chinook Weir 445 Absent NTD R5a

10/9/2007 Chinook Weir 0 Unknown NTD R5a




Survey 770 Absent 062411 R4 Spring 2004 CDWR

Wickland

Oil Net Pet

Feather

River





a Most CWT recoveries on Clear Creek are made by California Department of Fish and Game during their fall Chinook salmon carcass

survey and are not included in this report. b NTD = No tag detected.

c Collected during supplemental snorkel survey of Reach 6, not discussed in this report.

26

TABLE 11.—Age structure of adult spring Chinook carcasses sampled in Clear Creek since 2003. Age determinations were made by

reading scales from carcasses recovered in Reach 1-5a (upstream of the picket weir). Table includes total number of scales read (n=)

and the percent sampled of total carcasses counted in Reaches 1-5a.

year 2003 2004 2005 2006 2007

n= 23 33 55 46 54

Percent of total

carcasses sampled 92% 73% 82% 74% 77%

age 2 13% 70% 24% 13% 31%

age 3 78% 21% 65% 83% 67%

age 4 9% 9% 11% 4% 2%

TABLE 12.—Clear Creek temporary picket weir installation dates and monitoring days from 2003-2007. Beginning in 2006, the

location of the picket weir was either at Reading Bar (RB) or at Shooting Gallery (SG), based upon the percent of SCS holding in the

large pool between the weir sites.

Survey year Weir location a Date installed Date removed Days installed Days monitored

2003 RB 2-Sep 3-Nov 63 48

2004 RB 26-Aug 1-Nov 68 67

2005 RB 25-Aug 15-Nov 83 72

2006 SG and RB 24-Aug 1-Nov 70 38

2007 SG 23-Aug 1-Nov 71 44 a In 2006, the weir was installed at the SG site but after several incidents when pickets were lifted and fish passage was allowed, we installed a second weir at the

RB site on October 6. The second weir was in the creek for 27 days and monitored 11 days.

27

TABLE 13.—Total redds per reach and the minimum percent of incubation time that spring Chinook salmon eggs were exposed to

temperatures >56oF in Clear Creek in 2005-2007.

Reach 2005 2006 2007

1 16 (2.6%) 11 (0%) 18 (0%)

2 15 (6.3%) 16 (0%) 17 (0%)

3 4 (5.2%) 20 (0%) 2 (1.1%)

4 14 (9.7%) 22 (1.0%) 7 (0%)

5a 3 (18.9%) 13 (0%) 5 (1.0%)

Total 52 (6.7%) 82 (0.2) 49 (1%)

28

Figures

29

FIGURE 1.—Map of study area, Clear Creek, Shasta County, California, 2007.

30

FIGURE 2.—Live adult Chinook salmon observed during 2007 Clear Creek snorkel surveys. The temporary picket weir was located

between Reaches 5a and 5b. We closed the picket weir on August 23, following the Reach 5a snorkel survey, and removed it on

November 1. Reach 6 surveys ended on September 28

31

FIGURE 3.—Chinook salmon redds observed during 2007 Clear Creek snorkel surveys. The temporary picket weir was located

between Reaches 5a and 5b. We closed the picket weir on August 23, following the Reach 5a snorkel survey, and removed it on

November 1. Reach 6 surveys ended on September 28.

32

FIGURE 4.—Number of spring-run Chinook salmon redds observed during snorkel surveys of Clear Creek in Reaches 1-5a from

2003-2007, and the proportion of these redds that contained injection gravel.

33

0

5

10

15

20

25

30

2003 2004 2005 2006 2007

survey year

Reading Bar

Clear Creek Road Bridge

Placer

Guardian Rock

Need Bridge

Whiskeytown

red

ds

FIGURE 5.—Spring-run Chinook (SCS) salmon redds that contained injection gravel, observed during the Clear Creek snorkel

surveys of Reaches 1-5a from 2003 to 2007. Each year shows the number of redds that contained injection gravel and the number of

redds associated with the different gravel injection sites. The following sites did not have injection gravel available for spawning

until: Need Bridge site: 2004; Guardian Rock site: 2006; and Reading Bar site: 2006. The Reading Bar site gravel was actually first

available in 2003, however, it was downstream of the weir until 2006 and not available to SCS upstream of the weir.

34

0

50

100

150

200

250

2001 2002 2003 2004 2005 2006 2007

survey year

red

ds

FIGURE 6.—Redd counts during the final September survey of Clear Creek in Reach 6 since 2001. Each year, we carried out surveys

between September 23 and 29.

35

FIGURE 7.—Chinook salmon carcasses observed during 2007 Clear Creek snorkel surveys and weir monitoring. The temporary

picket weir was located between Reaches 5a and 5b. We closed the picket weir on August 23, following the Reach 5a snorkel survey,

and removed it on November 1. Reach 6 surveys ended on September 28.

36

0

1

2

3

4

5

6

8/2

3/2

00

7

8/3

0/2

00

7

9/6

/20

07

9/1

3/2

00

7

9/2

0/2

00

7

9/2

7/2

00

7

10

/4/2

00

7

10

/11

/20

07

10

/18

/20

07

10

/25

/20

07

11

/1/2

00

7

num

ber

Un-spawned female

FIGURE 8.—Chinook salmon carcasses retrieved during 2007 Clear Creek weir monitoring, upstream of the weir. Weir monitoring

occurred 3-5 days per week with no more than two days between checks.

37

FIGURE 9.—Box plots comparing the distribution of fork lengths for spring-run Chinook salmon carcasses recovered upstream of the

weir during weir monitoring and snorkel surveys, from 2003-2007. Whiskers represent the 5th and 95th percentiles.

38

FIGURE 10.—Box plot representing fork length distribution from spring-run Chinook salmon carcasses recovered during snorkel

surveys and weir monitoring upstream of the weir in 2007. The median fork length from carcasses recovered on the weir was

significantly different from the carcasses recovered from the snorkel survey (n=25 for each survey). Whiskers represent the 5th and

95th percentiles.

39

0

5

10

15

20

25

30

35

Weir Snorkel Weir Snorkel Weir Snorkel Weir Snorkel Weir Snorkel

2003 2004 2005 2006 2007

nu

mb

er female

male

unknown

FIGURE 11.—Number of males, females, and unknown gender Chinook salmon carcasses counted upstream of the Clear Creek picket

weir during snorkel and weir surveys between 2003 and 2007.

40

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

weir snorkel

method

perc

en

t

unknown

male

female

FIGURE 12.—Percent of male, female, and unknown carcasses recovered during Clear Creek snorkel surveys and weir monitoring

from 2003-2007.

41

0

2

4

6

8

10

12

400 450 500 550 600 650 700 750 800 850 900 950 1000 1050

fork length (mm)

AGE 2 AGE 3

nu

mb

er

FIGURE 13.—Age composition and fork length distribution of Chinook salmon carcasses retrieved upstream of the weir during 2007

Clear Creek snorkel and picket weir monitoring surveys in Reaches 1-5a.

42

FIGURE 14.—Installation of the 2007 Clear Creek temporary picket weir monitoring site at Shooting Gallery.

43

45.00

47.00

49.00

51.00

53.00

55.00

57.00

59.00

61.00

63.00

65.00

67.00

69.00

71.00

73.00

75.00

4/1

/2007

4/1

5/2

007

4/2

9/2

007

5/1

3/2

007

5/2

7/2

007

6/1

0/2

007

6/2

4/2

007

7/8

/2007

7/2

2/2

007

8/5

/2007

8/1

9/2

007

9/2

/2007

9/1

6/2

007

9/3

0/2

007

10/1

4/2

007

10/2

8/2

007

tem

pera

ture

(F)

0

50

100

150

200

250

300

350

flow

(cf

s)

MDT at LRST

MDT at IGO

temperature criteria at IGO

MDF at IGO

FIGURE 15.—Mean daily water temperature (MDT) and mean daily flow (MDF) at the Igo gage (RM 10.9) with temperature criteria

for spring Chinook salmon (SCS) holding (60°F) and egg incubation (56°F). Also includes MDF at the end of Reach 6 at the

RBFWO lower rotary screw trap (LRST) (river mile 1.7).

44

48

50

52

54

56

58

60

62

64

66

68

70

9/1

/07

9/8

/07

9/1

5/0

7

9/2

2/0

7

9/2

9/0

7

10

/6/0

7

10

/13

/07

WhiKanaIgotemperature criteria at IgoCcrbGcRrLcc

48

50

52

54

56

58

60

62

64

66

68

70

6/1

/07

6/8

/07

6/1

5/0

7

6/2

2/0

7

6/2

9/0

7

7/6

/07

7/1

3/0

7

7/2

0/0

7

7/2

7/0

7

8/3

/07

8/1

0/0

7

8/1

7/0

7

8/2

4/0

7

8/3

1/0

7

9/7

/07

9/1

4/0

7

WhiKanaIgotemperature criteria at IgoCcrbGcRrLcc

FIGURE 16.—Mean daily water temperatures (MDTs) at select temperature monitoring sites in

Clear Creek, 2007. Top figure shows MDT during the 60°F water temperature criteria period

(June 1-September 14) at Igo. Bottom figure shows MDT during the spring Chinook salmon

spawning period and when the 56°F water temperature criteria period (September 15) at Igo

begins.

45

0

20

40

60

80

100

120

140

160

180

200

2003 2004 2005 2006 2007

survey year

August Index upstream of weir

redds upstream of weir

carcasses weir

carcasses snorkel

nu

mb

er

FIGURE 17.—Relationship between the spring Chinook salmon August index, redd counts, and carcass counts upstream of the weir

on Clear Creek from 2003-2007.

Documents

Adult Spring Chinook Salmon Monitoring in Clear Creek, California: 2007 Annual Report. BC/Clear Creek Monitoring... · 2017. 11. 16. · weir to spatially separate SCS and fall Chinook