M.A. Jepson | Geology Reports

USGS2009

Adult chinook salmon passage at Little Goose Dam in relation to spill operations

Spill patterns at Little Goose Dam in 2007 were modified in anticipation of a spillway weir installation intended to improve downstream passage of juvenile salmonids. However, in spill pattern was associated with reduced daily counts of adult salmon passing the dam. Consequently, the behaviors and upstream passage times of radio-tagged adult spring–summer Chinook salmon were evaluated in response to three spillway discharge patterns at Little Goose Dam during 2008. Simultaneously, tailrace conditions were characterized by monitoring the downstream paths of GPS-equipped drogues. Two of the spill treatments (i.e., Bulk and Alternate) were variations of patterns thought to mimic those produced if a spillway weir was installed. The third treatment (Uniform) was characterized by spilling similar volumes of water through most spillbays.

Washington↗

USGS2004

Stock-specific migration timing of adult spring-summer Chinook salmon in the Columbia River basin

An understanding of the migration timing patterns of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss is important for managing complex mixed-stock fisheries and preserving genetic and life history diversity. We examined adult return timing for 3,317 radio-tagged fish from 38 stocks of Columbia River basin spring-summer Chinook salmon O. tshawytscha over 5 years. Stock composition varied widely within and between years depending on the strength of influential populations. Most individual stocks migrated at similar times each year relative to overall runs, supporting the hypotheses that run timing is predictable, is at least partially due to genetic adaptation, and can be used to differentiate between some conspecific populations. Arrival timing of both aggregated radio-tagged stocks and annual runs was strongly correlated with river discharge; stocks arrived earlier at Bonneville Dam and at upstream dams in years with low discharge. Migration timing analyses identified many between-stock and between-year differences in anadromous salmonid return behavior and should and managers interested in protection and recovery of evolutionary significant populations.

North American Journal of Fisheries Management↗