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(E.3.1-3) (Chapter 1) the Timing and Distribution of Fall Chinook Salmon Spawning Downstream of the Hells Canyon Complex

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(E.3.1-3) (Chapter 1) the Timing and Distribution of Fall Chinook Salmon Spawning Downstream of the Hells Canyon Complex Evaluation of Anadromous Fish Potential Within the Mainstem Snake River, Downstream of the Hells Canyon Complex of Reservoirs Phil Groves Editor Technical Report Appendix E.3.1-3 December 2001 Hells Canyon Complex FERC No. 1971 Copyright © 2003 by Idaho Power Company The Timing and Distribution of Fall Chinook Salmon Spawning Downstream of the Hells Canyon Complex Phillip A. Groves Anadromous Fisheries Biologist Technical Report Appendix E.3.1-3 Evaluation of Anadromous Fish Potential Within the Mainstem Snake River, Downstream of the Hells Canyon Complex of Reservoirs Chapter 1 December 2001 Hells Canyon Complex FERC No. 1971 Copyright © 2003 by Idaho Power Company Idaho Power Company Chapter 1: Fall Chinook Spawn Timing and Distribution TABLE OF CONTENTS Table of Contents............................................................................................................................. i List of Tables ................................................................................................................................. iii List of Figures................................................................................................................................ iii Abstract............................................................................................................................................1 1. Introduction.................................................................................................................................2 2. Study Area ..................................................................................................................................3 3. Methods.......................................................................................................................................4 4. Results.........................................................................................................................................5 1991............................................................................................................................................5 1992............................................................................................................................................6 1993............................................................................................................................................6 1994............................................................................................................................................7 1995............................................................................................................................................7 1996............................................................................................................................................7 1997............................................................................................................................................8 1998............................................................................................................................................8 1999............................................................................................................................................9 2000............................................................................................................................................9 5. Discussion...................................................................................................................................9 5.1. Temperature and Spawn Timing......................................................................................10 5.2. Thermal Alterations at the HCC ......................................................................................11 5.3. Flow Levels and Spawn Distribution...............................................................................13 6. Summary and Conclusions .......................................................................................................15 Hells Canyon Complex Page i Evaluation of Anadromous Fish Potential Idaho Power Company 7. Acknowledgments.....................................................................................................................17 8. Literature Cited .........................................................................................................................17 Page ii Hells Canyon Complex ,GDKR3RZHU&RPSDQ\ &KDSWHU)DOO&KLQRRN6SDZQ7LPLQJDQG'LVWULEXWLRQ /,672)7$%/(6 7DEOH 0HDQGLVFKDUJHWKURXJKRXWWKHVSDZQLQJVHDVRQZLWKLQHDFKRIWKHPDMRU 6QDNH5LYHUVHJPHQWV± 7DEOH -XOLDQZHHNRIDHULDOUHGGVXUYH\VDQGFRUUHVSRQGLQJQHZUHGGVREVHUYHG GXULQJHDFKVXUYH\± 7DEOH 7KHWRWDOQXPEHURIVKDOORZDQGGHHSZDWHUUHGGVREVHUYHGLQWKH 6QDNH5LYHUEHWZHHQ$VRWLQ:DVKLQJWRQDQGWKH+HOOV&DQ\RQ'DP 5.0± ± 7DEOH 7RWDOQXPEHURIUHGGVREVHUYHGGXULQJDHULDOVXUYH\VRIWKHPDMRU WULEXWDULHVWRWKH6QDNH5LYHU± 7DEOH +LVWRULFIDOOFKLQRRNVDOPRQUHGGVXUYH\VDQGFRUUHVSRQGLQJQXPEHURI UHGGVLGHQWLILHG 7DEOHD 7KHQXPEHURIUHGGVFRQVWUXFWHGGXULQJHDUO\SHULRGVRIVSDZQLQJ GRZQVWUHDPRIWKH6DOPRQ5LYHUFRQIOXHQFHZKHQWHPSHUDWXUHVDUH GURSSLQJIURPMXVWDERYHWR&± 7DEOHE 7KHQXPEHURIUHGGVFRQVWUXFWHGGXULQJHDUO\SHULRGVRIVSDZQLQJ XSVWUHDPRIWKH6DOPRQ5LYHUFRQIOXHQFHZKHQWHPSHUDWXUHVDUH GURSSLQJIURPMXVWDERYHWR&± /,672)),*85(6 )LJXUHD 'LVWULEXWLRQRIVSDZQLQJDQGWRWDOQXPEHURIUHGGVREVHUYHGDQQXDOO\DW VSDZQLQJORFDWLRQVLGHQWLILHGGXULQJDHULDOVXUYH\VRIWKH6QDNH5LYHU EHWZHHQULYHUPLOHVDQG± )LJXUHE 'LVWULEXWLRQRIVSDZQLQJDQGWRWDOQXPEHURIUHGGVREVHUYHGDQQXDOO\DW VSDZQLQJORFDWLRQVLGHQWLILHGGXULQJDHULDOVXUYH\VRIWKH6QDNH5LYHU EHWZHHQULYHUPLOHVDQG± )LJXUHF 'LVWULEXWLRQRIVSDZQLQJDQGWRWDOQXPEHURIUHGGVREVHUYHGDQQXDOO\DW VSDZQLQJORFDWLRQVLGHQWLILHGGXULQJDHULDOVXUYH\VRIWKH6QDNH5LYHU EHWZHHQULYHUPLOHVDQG± +HOOV&DQ\RQ&RPSOH[ 3DJHLLL Evaluation of Anadromous Fish Potential Idaho Power Company Figure 2. Cumulative percent completion of spawning within the Snake River, by Julian week, 1991–2000. Data used for this graph is based on surveys conducted at the beginning of each Julian week....................................................35 Figure 3. A comparison of cumulative percent completion of spawning for 1991, 1992, 1998, 1999, and 2000...................................................................................36 Figure 4. A comparison of water temperatures recorded within the main Snake River near Swan Falls Dam (RKM 737), the head of Brownlee Reservoir (RKM 556), and downstream of the Hells Canyon Dam near Pittsburg Landing (RKM 348), May 1996–January 1999. ....................................37 Figure 5. The relationship of number of adult fall chinook salmon allowed to escape past Lower Granite Dam, comprising the Snake River spawning population, and the corresponding observed number of spawning sites being used, 1991–2000. .........................................................................................38 Page iv Hells Canyon Complex Idaho Power Company Chapter 1: Fall Chinook Spawn Timing and Distribution ABSTRACT Prior to 1991, very little was known about the timing and distribution of fall chinook salmon spawning within the Snake River. Such knowledge was crucial for Idaho Power Company (IPC) to implement a provisional flow program designed to benefit threatened fall chinook salmon. Therefore, in 1991, IPC joined with the Washington Department of Fisheries and Wildlife, U.S. Fish and Wildlife Service, U.S. Forest Service, and the Nez Perce Tribe in a cooperative effort to enhance spawning surveys within the Snake River Basin. Our main objectives were to identify the timing and distribution of spawning throughout the Snake River between Asotin, Washington, and the Hells Canyon Dam. Spawning surveys were conducted along the 165-km-long, free-flowing reach of the Snake River between Asotin and the Hells Canyon Dam generally from mid-October through mid-December, 1991 through 2000. Turbidity in our study area was generally low, permitting visual aerial and underwater video surveys to identify and enumerate fall chinook redds. Surveys conducted through the 1990s showed that spawning typically begins by mid-October, peaks by early November, and is essentially completed by late November. The number of fall chinook redds observed within the mainstem Snake River (shallow and deep-water inclusive) has increased over recent years from a low of 46 in 1991 to a high of 373 in 1999. Redd construction at water depths greater than 3.0 m (unsurveyed previous to 1991) can account for as much as 50% of the spawning activity within the mainstem Snake River but more commonly comprises about 30%. Spawning (both shallow and deep) has been observed throughout the free-flowing reach of the Snake River from about river kilometer (RKM) 239 to RKM 397, at 85 and 29 documented shallow and deep-water spawning locations, respectively. While the absolute number of specific locations used for spawning has tended to increase as escapement numbers have increased, during the highest level of use (1999–373 redds) only 35% of shallow and 38% of deep-water sites were used to the maximum ever documented. This evidence suggests that full seeding, or carrying capacity in terms of spawning, has not been attained at even the highest escapement levels. Fall chinook within the Snake River spawn during the descending limb of the thermal regime of the river, generally beginning as water temperatures reach 16.0 °C and ending as temperatures drop to 7.0 °C. However, we have observed that the initiation of spawning can begin when temperatures are as high as 17.0 °C or can be delayed
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