Draft Imnaha Subbasin Summary November 30, 2001 Prepared for the Northwest Power Planning Council Subbasin Team Leader



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Summer Steelhead


Snake River summer steelhead population distribution in the Imnaha subbasin was historically similar to current conditions. Although actual historic escapement data does not exist, it is estimated that prior to the construction of the four lower Snake River dams (in the early 1960’s - mid 1970’s), up to 4,000 A-run summer steelhead returned to the Imnaha subbasin on an annual basis (U. S. Army Corps of Engineers 1975). In the absence of historic distribution data, it is difficult to determine which streams were inhabited by summer steelhead. However the lack of residual rainbow trout above Imnaha Falls (RM 73) suggests that steelhead were likely restricted to all accessible areas downstream from this probable migration barrier (Mundy and Witty 1998).

Annual steelhead spawning surveys in the Imnaha are limited (USDA Forest Service 1998a; 1998b). Current escapement estimates are based on data collected in Camp Creek, a tributary to Big Sheep Creek. Camp Creek, a spring-fed stream, is used for annual redd surveys due to its accessibility, flows and water clarity during survey periods, and an early spawning group of fish (B. Knox, ODFW, personal communication, April 12, 2001). Annual escapement of wild/naturally spawning A-run fish has declined over the past three decades with recent estimates ranging from 300 to 1,000 adults. Summer steelhead redd counts in the lower six miles of Camp Creek are shown in Figure 13. The increase in the number of redds observed from 1985 to 1987 was consistent with trends observed during the same period throughout the Columbia basin (B. Knox, ODFW, personal communication, April 19, 2001) but may also be related to the Lower Snake River Compensation Program (LSRCP) facility constructed on Little Sheep Creek in 1982 (D. Bryson, NPT, personal communication, April 27, 2001).



Figure 13. Summer steelhead redd counts in the lower six miles of Camp Creek for the run years 1965-2000 (Streamnet database)


Quantification of adult steelhead abundance is generally lacking throughout the Imnaha River subbasin. Adult abundance monitoring via weirs has been limited to Little Sheep Creek from 1982 to present and Lightning Creek 2000 to present. Adult escapement monitoring in Lightning Creek enumerated 35 adults (34 natural origin and one hatchery origin). Run timing ranged from March 28 to June 8th, with 80% of the upstream movement occurring between April 10th and May 20th (Miller and Hesse Draft 2001).

Juvenile rearing density monitoring has been limited. Snorkeling observations have been conducted in Big Sheep Creek, Lick Creek, and in the mainstem Imnaha River from 1992 to 2000. Densities of juvenile O. mykiss (multiple year classes) were highest in Lick Creek, but never exceeded 0.5 fish/m2. (Table 14; Blenden and Kucera in prep 2001). Multiple pass electrofishing surveys were conducted in Lightning, Big Sheep, Little Sheep creek, and Gumboot creeks in 1999 and 2000. Densities of wild O. mykiss parr never exceeded 0.5 fish / m2 (Table 15; ODFW and NPT unpublished data).

Table 14. Snorkeling observations conducted in Big Sheep Creek, Lick Creek, and the Imnaha River (1992-2000).


Stream

Year

Habitat Type/

# of Transects

Mean Density

(#/100m2)

of Chinook

(age = 0+)

Mean Density

(#/100m2)

of Chinook

(age = 1+)

Mean Density

(#/100m2)

of Steelhead

Big Sheep Cr.

1992

Pool (3)

Run (4)


20.2

24.7


2.7

3.9


12.6

24.1


Big Sheep Cr.

1993

Pool (2)

Run (3)


17.2

5.6

4.6

5.3


25.4

15.5


Upper Big Sheep Cr. (7/7)

1994

Pool (2)

Run (2)


0.0

0.0


0.0

0.0


36.2

26.2


Upper Big Sheep Cr. (8/16)

1994

Pool (2)
Run (2)

8.3

(317.60)


2.4

(166.46)


0.0
0.0

24.9
16.0

Lower Big Sheep Cr. (7/8)

1994

Pool (2)

Run (4)


18.6

13.5

0.0

1.8


28.0

20.8


Lower Big Sheep Cr. (8/17)

1994

Pool (2)
Run (4)


22.2

(12.88)


16.1

(1.78)


0.0
1.2

19.5
25.5

Big Sheep Cr.

1995

Pool (3)

Run (3)


0.0

0.0


1.8

0.6


18.9

22.0


Imnaha River

1992

Pool (5)

Run (8)


40.6

16.3


0.7

0.2

2.0

2.8


Imnaha River

1993

Pool (5)

Run (8)


61.7

17.9


1.5

1.1


2.9

1.5


Imnaha River

1994

Pool (5)

Run (8)


72.4

38.0


2.2

0.1


0.4

0.5


Imnaha River

1995

Pool (5)

Run (7)


36.2

16.5


1.1

1.2


1.8

1.6


Imnaha River

1996


Pool (5)

Run (7)


30.4

9.8


5.3

1.6


2.5

2.4


Upper Lick Cr. (7/7)

1994

Pool (3)

Run (3)


314.4

200.8


0.0

0.0


13.4

19.5


Upper Lick Cr.

(8/16)


1994

Pool (3)

Run (3)


224.0

208.8


0.0

0.0


23.9

30.2


Lower Lick Cr.

(7/7)

1994


Pool (3)

Run (3)


0.0

2.0


0.0

0.0


41.4

29.4


Lower Lick Cr.

(8/16)


1994

Pool (3)
Run (3)


37.2

(6.37)


39.0

(2.42)


0.0
0.0

38.0
37.7

Lick Cr

1996

Pool (7)

Run (7)


0.0

0.0


0.0

0.0


19.0

9.8


Lick Cr.

1997

Pool (6)

Run (5)


0.0

0.0


0.0

0.0


21.3

15.9


Lick Cr.

1998

Pool (6)

Run (4)


149.3

76.0


1.0

0.0


24.0

13.9


Lick Cr.

1999

Pool (6)

Run (4)


47.3

32.5


5.4

2.1


11.7

13.7

Table 15. Juvenile O. mykiss rearing density (Number/m2) estimates for Lightning, Big Sheep, Little Sheep creek, and Gumboot creeks in the Imnaha River subbasin, 1999 and 2000. ODFW and NPT unpublished data collected under LSRCP evaluation studies.


Year

Stream

Reach

Wild age 0

Wild age 1

Wild age 2+

Hatchery age 0

Hatchery age 1

Hatchery age 2+

1999

Little Sheep Cr.


1

0.094

0.010

0.00

0.754




0.136

2

0.198

0.005

0.005

0.166





0.005

3

0.209

0.023

0.004

0.039




0.009

4

0.020

0.020

0.031

1.552




0.060

5

Not sampled in 1999

6

0.093

0.061

0.008

1.089




0.030

Gumboot Cr.



1

0.229

0.172

0.111









2

0.217

0.084

0.059










3

0.033

0.202

0.118










4

0.381

0.184

0.110










5

0.019

0.164

0.104










6

0.253

0.349

0.245







Big Sheep Cr.



1

0.129

0.074

0.050

0.350




0.000

2

0.039

0.177

0.078

0.624




0.008

3

0.004

0.018

0.012

1.129




0.000

4

0.004

0.042

0.011

2.101




0.004

Lightning Cr.


1

0.122

0.191

0.028










2

0.172

0.168

0.035










3

0.081

0.078

0.036










4

0.106

0.066

0.062










2000

Little Sheep Cr.


1

0.238

0.037

0.000




0.044

0.030

2

0.355

0.022

0.000




0.000

0.008

3

0.474

0.029

0.004




0.033

0.000

4

0.358

0.005

0.019




0.150

0.005

5

0.608

0.037

0.005




0.042

0.000

6


0.111

0.011

0.011




0.071

0.000

Gumboot Cr.



1

1.859

0.125

0.066










2

0.956

0.081

0.000










3

0.259

0.219

0.084










4

0.259

0.104

0.025








5

0.202

0.061

0.074










6

0.000

0.085

0.000









Big Sheep Cr.



1

0.326

0.040

0.004

0.000

0.036

0.009

2

0.211

0.088

0.046

0.000

0.077

0.023

3

0.111

0.019


0.003

0.000

0.123

0.000

4

0.104

0.011

0.004

0.008

0.118

0.000

5

0.167

0.035

0.006

0.000

0.004

0.061

6

0.213

0.077

0.009

0.000

0.018

0.131

Lightning Cr.



1

0.000

0.162


0.017










2

0.191

0.123

0.037










3

0.140

0.080

0.060










4

0.253

0.103

0.053








Season-wide estimates of juvenile steelhead survival from the mouth of Imnaha River to Lower Granite Dam have been made since 1993. Survival estimates of spring emigrating natural steelhead have ranged from 0.860 in 1998 to 0.901 in 1997 (Figure 14; Cleary et al. 2000, in prep.). Survival estimates of hatchery steelhead smolts have ranged from 0.646 in 1996 to 0.829 in 1998 (Figure 15; Cleary et al. 2000, in prep.). Arrival timing of Imnaha river juvenile natural and hatchery steelhead at Snake River Dams has been tracked since 1993 (Table 16 and Table 17).



Figure 14. Season-wide estimates for natural steelhead released from the Imnaha River trap to Lower Granite Dam, from 1995 to 1999. Error bars indicate the 95% confidence limit (modified from Cleary et al 2000 and Cleary et al. in prep.)

Figure 15. Season-wide estimates for hatchery steelhead released from the Imnaha River trap to Lower Granite Dam, from 1995 to 1999. Error bars indicate the 95% confidence limit (modified from Cleary et al 2000 and Cleary et al. in prep.)


Table 16. Arrival timing of PIT tagged Imnaha River natural steelhead smolts at Lower Granite, Little Goose, Lower Monumental, and McNary dams from 1993 to 1999.

Impoundment

Year

Sample Size

n

Date Range

Arrival Timing

From

To

Median

90%

Lower Granite


1999

649

Apr 19

Jun 26

May 18

Jun 5




1998

1,474

Apr 2

Jun 12

May 3

May 22




1997

368

Apr 20

Jul 10

May 8

May 24




1996

537

Apr 19


Jun 10

May 6

Jun 4




1995

128

Apr 28

Jun 19

May 2

May 9




19941

332

Apr 25

Aug 15

May 8

Jun 1




19942

207

May 3

Aug 20

May 9

May 30





1993

101

May 3

Jun 13

May 26

Jun 8

Little Goose

1999

717

Apr 8

Jun 24

May 21

May 25




1998

481

Apr 14

Jun 19

May 8

May 26




1997

319

Apr 20

Jun 19

May 10

May 26





1996

365

Apr 20

Jun 14

May 9

May 28




1995

70

May 1

Jun 23

May 7

May 12




19941

159

Apr 29

Jul 29

May 12

May 31




19942

121

May 6

Jul 26

May 15

Jun 1





1993

48

May 6

Jun 11

May 24

Jun 7

Lower Monumental

1999

342

Apr 19

Jun 21

May 23

May 27




1998

213

Apr 16

Jun 11

May 10

May 27




1997

264

Apr 21

Jun 6

May 11

May 25





1996

397

Apr 22

Jun 15

May 14

May 29




1995

81

May 3

May 17

May 9

May 14




19941

148

May 1

Aug 8

May 12

Jul 8




19942

91

May 9

Jul 31

May 15

Jul 10


1993

43

May 6

Jun 15

May 30

Jun 11

McNary

1999

55

Apr 17

May 31

May 25

May 27




1998

53

Apr 20

Jun 4

May 7

May 28




1997

62

Apr 24

Jun 5

May 13

May 18




1996

157

Apr 25


Jun 11

May 11

May 21




1995

35

May 5

May 27

May 11

May 17




19941

66

May 5

Jun 22

May 18

Jun 9




19942

42

May 13

Jun 25

May 18

Jun 6




1993

17

May 11

Jun 13

May 25


May 31

1 NPT PIT tagged fish

2 FPC PIT tagged fish

Table 17. Arrival timing of PIT tagged Imnaha River hatchery steelhead smolts at Lower Granite, Little Goose, Lower Monumental, and McNary dams from 1993 to 1999.



Impoundment

Year

Sample Size

n

Date Range

Arrival Timing

From

To

Median

90%

Lower Granite

1999

1,973

Apr 18

Aug 5

May 24

Jun 18




1998

1,683


Apr 25

Jul 29

May 15

May 26




1997

2,346

Apr 19

Jul 24

May 23

Jun 13




1996

440

Apr 23

Jul 14

May 28

Jun 14




1995

661

May 6

Jul 12

May 31

Jun 16




19941

164


Apr 29

Aug 20

May 29

Jul 15




19942

306

May 6

Aug 21

May 25

Jun 23




1993

224

May 3

Jun 28

May 17

May 31

Little Goose

1999

1,593

Apr 20

Aug 22

May 25

Jun 18




1998

555


May 3

Jul 10

May 25

May 30




1997

1,844

Apr 21

Aug 23

May 26

Jun 13




1996

261

Apr 24

Jul 11

May 25

Jun 16




1995

409

May 8

Jul 13

Jun 3

Jun 20




19941

86

May 2


Jul 30

May 31

Jul 17




19942

165

May 10

Aug 12

May 27

Jul 9




1993

106

May 5

Jul 8

May 25

Jun 2

Lower Monumental

1999

790

Apr 21

Jul 20

May 26

Jun 19




1998

253

May 5


Jul 15

May 26

Jun 3




1997

1,432

Apr 22

Aug 6

May 27

Jun 15




1996

232

May 6

Jul 7

May 27

Jun 15




1995

410

May 9

Jul 13

Jun 6

Jun 16




19941

30

May 5

Aug 5


Jun 3

Jul 17




19942

75

May 11

Aug 24

Jun 18

Jul 21




1993

92

May 7

Jun 14

May 26

Jun 5

McNary

1999

79

Apr 27

Jul 8

May 28

May 31




1998

31

May 13

Jul 2

Jun 1

Jun 19





1997

245

Apr 23

Aug 12

May 27

Jun 18




1996

30

Apr 27

Jul 3

May 23

Jun 7




1995

69

May 15

Jul 17

Jun 5

Jun 27




19941

22

May 17

Jul 14

Jun 5

Jul 10



19942


56

May 20

Jul 11

Jun 17

Jul 8




1993

7

May 11

Jun 5

May 19

May 30

Imnaha steelhead are generally ubiquitous where other salmonids are found. Currently, Imnaha steelhead maintain widespread distribution throughout most of the subbasin, and generally occur in all tributaries that do not have vertical falls near their mouths (Mundy and Witty 1998). Approximately 397.6 river miles of summer steelhead spawning and rearing habitat have been identified in the Imnaha subbasin (Figure 16; USDA Forest Service 1998a; 1998b).

Figure 16. Summer steelhead spawning and rearing areas in the Imnaha subbasin. Due to scale (1:100,000), not all streams containing steelhead are shown (Streamnet data).

The summer steelhead fishery on the Imnaha was closed in 1974 due to declining adult returns, as indicated by adult counts at Ice harbor Dam on the Snake River (U.S. Army Corps of Engineers 1990) and low redd counts at index sites (U.S. Fish and Wildlife Service 1991). Under the auspices of the Lower Snake River Compensation Project (LSRCP), which was initiated in 1982, Imnaha steelhead populations were augmented by hatchery produced fish in an effort to restore a tribal and recreational fishery (Carmichael 1989). A consumptive-based recreational summer steelhead fishery on ad-clipped hatchery origin fish was subsequently re-opened in 1986 due to increased returns from the hatchery program (Figure 17) (Flesher et al. 1993).



No harvest period

Figure 17. Estimated annual steelhead harvest in the Imnaha subbasin for the run years 1956-1994 (Streamnet data 2001).


Annual creel surveys for Imnaha steelhead have been conducted by the Oregon Department of Fish and Wildlife since the fishery reopened in 1986. The surveys, which are typically conducted in the spring, provide managers with annual harvest information needed to assess LSRCP objectives and compensation goals. Results from creel surveys for the run years 1986-1998 are shown in Table 18.

Table 18. Creel survey results for summer steelhead caught in the Imnaha River for the run years 1987-1998 (ODFW data presented in Carmichael et al. 1989a; 1989b; Carmichael et al. 1991; Flesher et al. 1992; Flesher et al. 1994a; 1994b; Flesher et al. 1995; 1996; 1997; 1999)



Run

Year

No.

Anglers

Effort

(Hrs.)

Catch

Catch Rate Index

(hrs./fish)

# Wild

# Hatchery kept

1986-92


Punchcard Data Only

1992-93

789

2,910

130

171

8.0

1993-94

298

1,336

72

29

13.0

1994-95

219

1,048

39

24

17.0

1995-96

588

2,599

210

112

7.0

1996-97

2091

N/A

N/A


971

6.0

1997-98

1111

N/A

N/A

271

10.0

1/Value represents a subsample of total




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