Emigration of Natural and Hatchery Chinook Salmon and Steelhead Smolts from the Imnaha River, Oregon, Progress Report 2000-2002.

Cleary, Peter ; Kucera, Paul ; Blenden, Michael

United States. Bonneville Power Administration.

关键词: Granites;    Abundance;    Salmon;    Monitoring;    Juveniles;   

DOI  :  10.2172/962679
RP-ID  :  DOE/BP-00004004-2
RP-ID  :  4004
RP-ID  :  962679

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report summarizes the emigration studies of the Nez Perce Tribe in the Imnaha River subbasin during the 2001 and 2002 migration years. A migration year for the Imnaha River is defined here as beginning July 31 of the previous year and ending July 30 the following year. The conclusion of the studies at the end of migration year 2002 marked the 11th year of the Nez Perce Tribe's Lower Snake River Emigration Studies. The Nez Perce Tribe has participated in the Fish Passage Center's Smolt Monitoring Program for nine of the 11 years. These studies collect and tag juvenile chinook salmon and steelhead at two locations in the fall, rkm 74 and rkm 7, and at rkm 7 during the spring. Data from captured and tagged fish provide an evaluation of hatchery production and releases strategies, post release survival of hatchery chinook salmon, abundance of natural chinook salmon, and downstream survival and arrival timing of natural and hatchery chinook salmon and steelhead. The hydrologic conditions that migrating fish encountered in 2001 were characterized as a drought and conditions in 2002 were characterized as below average. Hatchery chinook salmon had a mean fork length that was 34 mm greater in 2001 and 35 mm greater in 2002 than the mean fork length of natural chinook smolts. Hatchery steelhead smolt mean fork lengths were 39 mm greater than natural steelhead smolts in 2001 and 44 mm greater than natural steelhead smolt fork lengths in 2002. A significant difference (p < 0.05) between hatchery and natural chinook salmon and steelhead fork lengths has been documented by these emigration studies from 1997 to 2002. Hatchery chinook salmon were volitionally released in 2001 and 2002 and the 90% arrivals for 2001 and 2002 at the lower rkm 7 trap were within the range of past observations of 22 to 38 days observed in 1999 and 2000. We estimated that 93.9% of the 123,014 hatchery chinook salmon released in 2001 survived to the lower trap and 90.2% of the 303,769 hatchery chinook salmon released in 2002 survived to the lower trap. Post release survival estimates for hatchery chinook salmon were within the range of past estimates; 88.4% in 1998 to 100.9% in 1994. An estimated 7,646 to 23,249 (95% C.I.) natural chinook salmon smolts migrated past the lower Imnaha River trap from April 4 to April 22. An additional 6,767 to 14,706 (95% C.I.) natural chinook salmon smolts migrated past the lower Imnaha River trap from April 23 to May 14, 2002. Natural chinook salmon captured and tagged at the upper rkm 74 trap survived to Lower Granite Dam (LGR) at a rate of 28.8% during migration year 2001 and 21.9% during migration year 2002. The survival estimate for fall tagged natural chinook salmon from the lower trap to LGR was 41.9% in 2001 and 33.3% in 2002. Differences between survival from release to LGR for fall tagged natural chinook salmon from the lower trap have been 5.9% to 16.9% higher than for fall tagged natural chinook salmon from the upper trap from 1994 to 2002. Spring PIT tag release groups of natural chinook salmon, hatchery chinook salmon, and hatchery steelhead produced estimates of survival from the trap to LGR within the range of past estimates since 1993. Estimated survival from release to LGR for 2001 and 2002 were as follows: 83.7% and 86.9% for natural chinook salmon, 80.3% and 77.3% for hatchery chinook salmon, 82.7% and 81.8% for natural steelhead, and 82.0% and 83.0% for hatchery steelhead. Estimates of survival for spring tagged fish from the trap to Lower Monumental Dam (LMO) during the drought of 2001 were the lowest estimates of survival from 1998 to 2002 for natural chinook salmon, and from1997 to 2002 for natural and hatchery steelhead. Estimates of migration year 2001 survival from the trap to LMO were as follows: 65.6% - natural chinook salmon, 68.9% - hatchery chinook salmon, 49.7% natural steelhead, and 42.9% - hatchery steelhead. Estimates of migration year 2002 survival from the trap to LMO were as follows: 76.8% - natural chinook salmon, 68.1% - hatchery chinook salmon, 69.9% natural steelhead, and 78.0% - hatchery steelhead. A smolt-to-adult return rate (SAR) index from LGR to LGR was calculated for migrating pre-smolt and smolt natural chinook salmon, that were PIT tagged in the fall and spring at the lower trap, for brood years 1996 to 1998 (migration years 1998 to 2000). The SARs are representative of in-river Imnaha natural chinook salmon. The LGR to LGR SAR index for presmolt chinook salmon is as follows: 3.08% (BY 1996), 2.41% (BY 1997), and 2.98% (BY 1998). Smolt-to-adult return rate index for spring tagged smolts was lower: 1.75% (BY 1996), 2.24% (BY 1997) and 2.94% (BY 1998). Fall tagged natural chinook salmon from the upper and lower trap and spring tagged natural chinook salmon from the lower trap all had significantly different (p < 0.05) median and cumulative arrival timing at LGR during migration year 2001.