Smolt Monitoring at the Head of Lower Granite Reservoir and Lower Granite Dam, 2005 Annual Report.

Abstract

This project monitored the daily passage of Chinook salmon Oncorhynchus tshawytscha, steelhead trout O. mykiss, and sockeye salmon O. nerka smolts during the 2005 spring out-migration at migrant traps on the Snake River and Salmon River. In 2005 fish management agencies released significant numbers of hatchery Chinook salmon and steelhead trout above Lower Granite Dam that were not marked with a fin clip or coded-wire tag. Generally, the age-1 and older fish were distinguishable from wild fish by the occurrence of fin erosion. Age-0 Chinook salmon are more difficult to distinguish between wild and non-adclipped hatchery fish and therefore classified as unknown rearing. The total annual hatchery spring/summer Chinook salmon catch at the Snake River trap was 0.34 times greater in 2005 than in 2004. The wild spring/summer Chinook catch was 0.34 times less than the previous year. Hatchery steelhead trout catch was 0.67 times less than in 2004. Wild steelhead trout catch was 0.72 times less than the previous year. The Snake River trap collected 1,152 age-0 Chinook salmon of unknown rearing. During 2005, the Snake River trap captured 219 hatchery and 44 wild/natural sockeye salmon and 110 coho salmon O. kisutch of unknown rearing. Differences in trap catch between years are due to fluctuations not only in smolt production, but also differences in trap efficiency and duration of trap operation associated with flow. Trap operations began on March 6 and were terminated on June 3. The trap was out of operation for a total of one day due to heavy debris. FPC requested that the trap be restarted on June 15 through June 22 to collect and PIT tag age-0 Chinook salmon. Hatchery Chinook salmon catch at the Salmon River trap was 1.06 times greater and wild Chinook salmon catch was 1.26 times greater than in 2004. The hatchery steelhead trout collection in 2005 was 1.41 times greater and wild steelhead trout collection was 1.27 times greater than the previous year. Trap operations began on March 6 and were terminated on May 17 due to high flows. There were two days when the trap was taken out of service because of mechanical failure. Travel time (d) and migration rate (km/d) through Lower Granite Reservoir for passive integrated transponder (PIT) tagged Chinook salmon and steelhead trout marked at the Snake River trap were affected by discharge. Statistical analysis of 2005 data detected a relation between migration rate and discharge for hatchery Chinook but was unable to detect a relation for wild Chinook. The inability to detect a migration rate discharge relation for wild Chinook salmon was caused by a lack of data. For hatchery Chinook salmon there was a 1.8-fold increase in migration rate between 50 and 100 kcfs. For steelhead trout tagged at the Snake River trap, statistical analysis detected a significant relation between migration rate and lower Granite Reservoir inflow discharge. For hatchery and wild steelhead trout, there was a 2.2-fold and a 2.2-fold increase in migration rate, respectively, between 50 and 100 kcfs. Travel time and migration rate to Lower Granite Dam for fish marked at the Salmon River trap were calculated. Statistical analysis of the 2005 data detected a significant relation between migration rate and Lower Granite Reservoir inflow discharge for hatchery Chinook salmon, wild Chinook salmon, hatchery steelhead trout, and wild steelhead trout. Migration rate increased 4.2-fold for hatchery Chinook salmon, 2.9-fold for wild Chinook salmon and 2.5-fold for hatchery steelhead, and 1.7-fold for wild steelhead as discharge increased between 50 kcfs and 100 kcfs. Fish tagged with PIT tags at the Snake River and Salmon River traps were interrogated at four dams with PIT tag detection systems (Lower Granite, Little Goose, Lower Monumental and McNary dams). Because of the addition of the fourth interrogation site (Lower Monumental) in 1993 and the installation of the Removable Spillway Weir at Lower Granite Dam in 2001, caution must be used in comparing cumulative interrogation data. Cumulative interrogations at the four dams for fish marked at the Snake River trap were 84% for hatchery Chinook, 89% for wild Chinook, 94% for hatchery steelhead, and 93% for wild steelhead. Cumulative interrogations at the four dams for fish marked at the Salmon River trap were 71% for hatchery Chinook, 78% for wild Chinook salmon, 80% for hatchery steelhead trout, and 81% for wild steelhead trout.