Seasonal utilization of instream boulder structures by anadromous salmonids in Hurdygurdy Creek, California

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R-5’S FISH HABITAT RELATIONSHIP
TECHNICAL BULLETIN

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Numbers Au^'st, 1990

David D. Fuller
Pacific Southwest Forest and
Range Experiment Station
Areata, CA

Seasonal Utilization of Instream Boulder
Structures

by Anadromous Salmonids in
Hurdygurdy Creek, California

This study examined the seasonal responses of
juvenile salmonids to the placement of instream
boulder structures. Instream boulder structures
have been used extensively in efforts to increase
the amount of suitable rearing habitat for juvenile
salmonids when this habitat may be limiting.

Instream structures alter channel hydraulics
and can influence important habitat components
such as water velocity and depth, amount of

US. Department of Agriculture

Forest Service

Pacific Southwest Region

cover, and distribution of stream substrate. The
goal of these habitat manipulations has been to
increase fish productions. However, specific
habitat requirements of juvenile salmonids vary
with size, species, and season and have not been
thoroughly studied or defined (Reiser and Bjomn
1979).

Although much effort has been focused on
placing boulder structures into streams, few ef-
forts have been made to evaluate their effective-
ness. Past efforts have employed electrofishing
techniques at summer low-flow conditions to
quantify fish abundance. Ward and Slaney (1981),
Overton et al. (1981), Moreau (1984), West
(1984), House and Boehne (1985) and Brock
(1986) have reported substantial increases in fish
abundance in stream sections modified by in-
stream structures compared to either pre-project
data or control reaches.

In this study, the distribution and abundance of
salmonids in these two stream sections were
compared to two control reaches during winter,
spring, summer and fall using direct underwater
observation techniques. Habitat improvement
structures were placed into two sections of Hurdy-
gurdy Creek in 1981 by Six Rivers National For-
est. Boulder wing deflectors and boulder clusters

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were used to modify wide, shallow homogeneous
stream sections into narrower, deeper more com-
plex habitat favorable for rearing age 1+ and age
2+ steelhead parr.

Study Site

Hurdygurdy Creek is a third order tributary to
the South Fork Smith River in Del Norte County,
California, that drains a 78 sq. km watershed
composed of mountainous Douglas Fir forest.
Mean annual rainfall is approximately 250 cm and
stream discharge ranges from 0.5 cubic meters per
second (cms) to peaks of 140 cms. Mean daily
stream temperature ranges from 5.0 degrees C to
21.0 degrees C (U.S. Forest Service 1979).

The stream supports populations of steelhead
trout (Oncorhynchus mykiss), Chinook salmon
(O. tshawytscha), and cutthroat trout {O. clarki).
All habitat improvements have been located on
the lower 7 km of the stream which has a mean
gradient of 1.7%.

Two reaches modified by boulder structures
were 50 m and 31m long. Structures were placed
into these sections beginning in 1 98 1 . Both reaches
contained a series of wing deflectors and boulder
clusters. Prior to boulder placement both reaches
were described as broad, shallow, low gradient
riffles (Moreau 1984). At the time of this study
both reaches were classified as pocket water and
run with edge water and backwater habitat types
located on the margins (McCain et al. 1990).

Two unmodified control sections were 28 m
and 40 m long. Both sections were classified as a
combination of low gradient riffle and run.

Methods

Data were collected during five sampling peri-
ods in January, March, May, August and October
1987. Two reaches modified by boulder struc-
tures and two control reaches were studied. Control
reaches were randomly selected from a stream

habitat type inventory (Decker et al. in progress).

Planar maps of the active channel were con-
structed incorporating major channel features for
each sampling period. Cross-sectional velocity
and depth measurements were taken for each sam-
pling period and plotted onto map overlays.

Distrubution and abundance of fish were deter-
mined by direct underwater observation using
techniques modified from Hankin and Reeves
(1988). Paired divers observed and recorded fish
species, location, total length, and behavior (feed-
ing, holding, or cruising) onto underwater slate
maps as they moved slowly upstream. The loca-
tions of each fish or group of fishes were plotted
onto map overlays for each sampling period. A
compensating polar planimeter was used to deter-
mine wetted surface areas from maps. Fish num-
bers were tabulated and fish densities were calcu-
lated. Comparing fish densities allows for direct
comparison of fish abundance in unequal-sized
study sections.

Results and Discusion

Physical Stream Conditions

The highest stream discharge, swiftest water
velocities, and greatest surface area volume oc-
cured during the March sampling period follow-
ing a storm event. Streamflow steadily decreased
through May and August and was lowest in
October. This was an exceptionally dry year
producing notably low streamflows all along the
Pacific coast. Water temperatures were: 6.0 de-
grees C. in January, 10.0 degrees C. in March, 17.0
degrees C. in May, 19.0 degrees C. in August, and
13.5 degrees C. in October.

Treated sections contained well defined, deep
thalwegs. Relatively large areas of low water ve-
locity (edgewater and backwater habitat types)
were found along the margins along the down-
stream edge of wing deflectors during all sampling
periods.

Control sections contained no defined thal-
wegs. During the January and March sampling pe-

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Figure 1 . Distribution of juvenile Chinook salmon (<) in a treated reach in
Hurdygurdy Creek, Co. in May 1 987.

ricxis the control sections contained very little
low velocity area which was limited to narrow
strips less than a meter wide along the stream-
bank.

Chinook Salmon

Although these stream improvement struc-
tures were originally placed into the stream to
increase suitable rearing habitat for juvenile
steelhead, juvenile chinook salmon were found
to utilize the slow water velocity margin habitat
created by the structures. Chinook salmon
began emerging from the streambed during
March and were observed most abundantly in
the shallow edgewater and backwater habitat
found along wing deflectors. Everest and
Chapman (1972) and McCain (1989) have de-
scribed this type of habitat to be highly selected
by newly emerged chinook salmon. Chinook
salmon were observed in these areas usually in

groups of 20 or more individuals (Figure 1).
Chinook salmon were five times as abundant in
the treated reaches than in control reaches during
the March and May sampling periods (Figure 2)
and were observed in very low frequency after
May. Areas of low water velocity were limited in
the control reaches during March and May pro-
viding little suitable habitat for chinook rearing
during that time. Chinook salmon were observed
only in a narrow strip of area along the stream
margin in control sections.

Steelhead

Young-of the-year (age 0+) steelhead began
emerging from the streambed in May and were
observed in the study sections through October.
Relative abundance of age 0+ steelhead in both
treated and control sections were similar.

Steelhead parr (age 1+ and age 2-t-) were the
target age class for these habitat improvement

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Number of Juvenile Chinook

1 25

1 00

75

50

25

JANUARY

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MARCH

gq

MAY

■ treated 1

□1 TREATED 2

□ CONTROL 1

□ CONTROL 2

AUGUST

OCTOBER

SAMPLING PERIOD

Figure 2. Number of juvenile chtnook salmon in tux) treated and two control
reaches tn Hurdygurdy Creek during five sampling periods in 1 987.

Densities of Steelhead Parr in May

A

Figure 3. Densities of steelhead parr in two treated and two control reaches in
Hurdygurdy Creek in May 1 987.

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Figure 4. Distribution of steelhead parr (X) in a treated reach in Hurdyurdy
Creek during May 1 987.

structures and were observed during all sampling
periods. Very few steelhead parr were observed
during January and March when water tempera-
tures were low and streamflows were relatively
high. Juvenile steelhead occupy interstitial spaces
in the streambed under winter conditions and
thus are generally not observable by divers. All
of the steelhead observed during January and
March were in close association with boulder
structures or large boulders. During the May
sampling period steelhead parr were found in
greater abundance and higher density (fish per
meter, fish per square meter, and fish per cubic
meter) in control reaches (Figure 3).

Streamflows in May were moderately high,
so the control sections were much deeper than
during summer low-flow conditions and steel-
head parr were observed throughout the control
sections generally associated with large boul-
ders. Steelhead parr observed in the treated
sections during May were found only near wing
deflectors and boulder clusters and absent from
the thalweg zones (Figure 4). Wing deflectors
focus the streamflow into the thalweg, resulting
in deeper, swifter habitat. Thalweg zone water
velocities during the May sampling period were

too great (in some areas in excess of 2.0 m/s) to be
usable habitat for steelhead parr.

During the August sampling period steelhead
parr were twice as numerous in the treated sec-
tions as in control sections. This is in agreement
with previous studies of juvenile steelhead utiliza-
tion of stream habitat improvement structures
during summer low-flow conditions. Ward and
Slaney (1981) examined the effectiveness of vari-
ous boulder structures in the Keogh River in
British Columbia. They found a favorable com-
parison of steelhead parr and juvenile coho salmon
(O. kisutch) densities between treated reaches
and reaches identified as prime rearing habitat.
Overton et al. (1981) found a 100% increase in
numbers of juvenile steelhead rearing in a boulder
enhanced reach compared to an adjacent unen-
hanced reach in Aikens Creek, California, one
year after boulder placement. Boulder structures
placed in the South Fork of the Salmon River,
California, resulted in a ten-fold increase in num-
bers of yearling steelhead trout per 100 linear feet
two years after placement (West 1984). House
and Boehne (1985) evaluated instream gabions
and boulder clusters placed into East Fork Lobster
Creek, Oregon, and found substantial increases in

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r

F

I

S

H

P

E

R

C

U

B

I

C

M

E

T

E

R

1 .0

0.8

0.6

0.4

0.2

0.0

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TREATED 1 □CONTROL 1
m TREATED 2 □ CONTROL 2

MAY

AUG

SAMPLING PERIOD

Figure 5. Number of steelhead parr per cubic meter observed in two treated and
two control reaches in Hurdygurdy Creek, CA in May and August 1987.

the number of rearing coho salmon and steelhead
trout. Brock (1986) compared pre and post treat-
ment numbers and biomass of 0+ and l-i- steel-
head trout in an enhanced vs. an unenhanced
reach in Red Cap Creek, California. Brock found
a 300% increase in numbers and a 146% increase
in relative biomass of yearling steelhead trout, as
well as increased numbers and biomass of sub-
yearling steelhead trout in the enhanced reach,
while the control reach showed a slight decrease
in the number of yearling steelhead trout and an
89% increase in the biomass of sub-yearling
steelhead trout.

Habitat improvement structures acted to in-
crease the depth and volume. Unfortunately,
exact pre-project volumes were not available for
this study. Brock (1986), House and Boehne
(1985), and Ward and Slaney (1981) all reported
an increase in water volume after placement of
boulder structures. Although steelhead parr were
twice as numerous in treated sections during
August, fish per cubic meter densities were nearly
equal with control reaches (Figure 5). This sug-
gests that greater water depth and volume were
important parameters in increasing steelhead
utilization of treated reaches.

Relatively few steelhead were observed in the
study sections during October. Low streamflows
during this time resulted in fish remaining in the
stream to occupy pool habitat.

Summary

Sampling on a seasonal basis provided an ex-
amination of temporal shifts in fish utilization of
habitat improvement structures, as well as the hy-
draulic response of treated reaches, as stream dis-
charge fluctuated.

Results show that newly emerged juvenile chi-
nook salmon utilize the low velocity habitat area
created by wing deflectors during the spring
(March-May) when such habitat is possibly lim-
ited. Steelhead parr use the deeper thalweg zones
created by the deflectors in late summer and early
fall.

Direct underwater observation was effective
throughout the year in Hurdygurdy Creek because
of good water clarity. Direct underwater observa-
tion allowed the distribution of fish to be docu-
mented within each reach, providing information
on usage of boulder structures by fish.

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Acknowledgements

This project was funded by the California
Department of Fish and Game, Six Rivers Na-
tional Forest, and the Pacific Southwest Forest
and Range Experiment Station, Areata, Califor-
nia. Thanks to Lynn Decker for initiating this
project and reviewing early drafts. Thanks to Tom
Lisle and Robert Thomas for technical advice, and
Kerry Overton for guidance throughout this proj-
ect. Special thanks to Mike McCain for help in
project design, data collection, and reviewing
drafts. Thanks to Annelise Carleton, Wendy Cole
and Amy Lind for reviewing drafts. Thanks to
Tim LaMarr, Pat Manley, John Pritchard, and
Jeannine Rossa for mapping.

Editor/Design by Stephanie Gomes
Six Rivers National Forest

^ Anyone wishing to submit a paper for

publication in the FHR CURRENTS, call Kerry
Overton or Stephanie Gomes (707) 442-1721 or
write to Six Rivers National Forest, Fisheries,

500 5th Street, Eureka, CA 95501 for guidelines
I and / or information. i

Literature Cited

Brock, W. A. 1986. Enhancement of rearing habi-
tat for juvenile steelhead trout {Salmo gairdneri)
by boulder placement in a tributary to the Klamath
River. M.S. Thesis. Humboldt State University,
Areata, California.

Decker, L.M., D.D. Fuller, and M.E. McCain (in
progress). Seasonal habitat utilization by anadro-
mous salmonids in Hurdygurdy Creek, Califor-
nia. Pacific Southwest Forest and Range Experi-
ment Station, Areata, California.

Everest, F.H. and D.W. Chapman 1972. Habitat
selection and spatial interaction by juvenile chi-

nook salmon and steelhead trout in two Idaho
streams. Journal of the Fisheries Research Board
of Canada 29(1) : 91-100.

Hankin, D.G. andG.H. Reeves 1988. Estimating
total fish abundance and total habitat area in small
streams based on visual estimation methods.
Canadian Journal of Fisheries and Aquatic Sci-
ences 45:834-844.

House, R.A. and P.L. Boehne 1985. Evaluation
of instream enhancement structures for salmonid
spawning and rearing in a coastal Oregon stream.
North American Journal of Fisheries Manage-
ment 5(2B) : 283-295.

McCain, M.E., D.D. Fuller, L.M. Decker, and
C.K. Overton 1990. Stream habitat classification
and inventory procedures for northern California.
FHR Currents Number One, U.S. Forest Service
Region 5 Fish-Habitat Relationships program
publication.

McCain, M.E. 1989. Natal stream rearing habitat
of juvenile chinook salmon in Hurdygurdy Creek,
California, in Proceedings of the 1988 Northeast
Pacific Chinook and Coho Workshoop, October
2-4, Nendels Inn, Bellingham, Washington.

Moreau, J.K. 1984. Anadromous salmonid en-
hancement by boulder placement in Hurdygurdy
Creek, California, pp. 97-1 16 mT. Hassler (ed.),
Proceedings: Pacific Northwest Stream Habitat
Management Workshop, October 10-12, 1984.
Humboldt State University, Areata, California.

Overton, K., W. Brock, J.Moreau, and J. Boberg
1981. Restoration and enhancement program of
anadromous fish habitat and populations on Six
Rivers National Forest. T. Hassler (ed.). Proceed-
ings: Propagation, Enhancement, and Rehabili-
tation of Anadromous Salmonid Populations and
Habitat Symposium, October 15-17, 1981.
Humboldt State University, Areata, California.

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Reiser, D.D. and T.C. Bjomn 1979. Habitat requirements of anadromous salmonids. General Technical
Report PNW-96, USD A Forest Service, Portland, Oregon.

U.S. Forest Service 1979. Water resource inventory for USDA Forest Service, Six Rivers National
Fore St, Eureka, California. Prepared by Ott W ater Engineers, Redding, California, under contract number
53-9A47-9-28.

West, J.R. 1984. Enhancement of salmon and steelhead spawning and rearing conditions in the Scott
and Salmon Rivers, California, pp. 1 17-127 in T. Hassler (ed.). Proceedings: Pacific Northwest Stream
Habitat management Workshop, October 10-12, 1984. Humboldt State University, Areata, California.

Ward, Br. and Slaney, P.A. 1981. Further evaluations of structures for the improvement of salmonid
rearing habitat in coastal streams of British Columbia. In T. Hassler (ed.) Proceedings: Propagation,
Enhancement and Rehabilitation of Anadromous Salmonid Populations and Habitat Symposium.
October 15-17, 1981 Humboldt State University, Areata, CA 168 pp.

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