Concurrent Sessions B: Integrating Fish Physiology or Behavior with Passage - Small Dams, Big Impacts; Adult Salmonid Migrations in the Umatilla River Basin

Like large hydropower counterparts in the Columbia River, low-elevation dams and irrigation diversions may impede adult salmonid migrations as fish approach spawning areas in smaller tributaries. The Umatilla River has seven low elevation dams that may obstruct Chinook salmon and steelhead access to historic spawning areas. We used radio telemetry to examine fallback rates, passage routes, rates, and delays, holding and spawning locations, and maximum upstream distribution of Chinook salmon and steelhead in the Umatilla River basin (Oregon). Analyses focused on the effects of project modifications on salmonid passage and overall system use by fish. Detections at fixed receivers and mobile tracking of 476 tagged steelhead, 130 spring Chinook salmon, and 206 fall Chinook salmon from 2009-2012 provided data for these analyses. Recent project modifications at individual diversion structures have resulted in marked improvements in fish passages times. Species show preference for different aspects of the modifications; for example, jump pools are used by spring Chinook more than steelhead. System passage times have also been markedly reduced. Locating key holding and spawning areas will provide information for additional habitat and restoration needs. The determination of upstream distribution and spawning of hatchery fish will allow managers to better assess the use of hatchery releases to supplement historical spawning areas

Passage behavior and survival of radio-tagged yearling Chinook salmon and steelhead at Ice Harbor Dam, 2007

Report of the National Marine Fisheries Service to the U.S. Army Corps of Engineers, Walla Walla, Washington</p

Passage behavior and survival of radio-tagged yearling Chinook salmon at Ice Harbor Dam, 2005

Report of the National Marine Fisheries Service to the US Army Coprs of Engineers, Walla Walla, Washington</p

Passage behavior and survival of river-run subyearling Chinook salmon at Ice Harbor Dam, 2005

Prepared by the National Marine Fisheries Service for the US Army Corps of Engineers, Walla Walla, Washington.</p

Passage behavior and survival of radio-tagged yearling and subyearling Chinook salmon and juvenile steelhead at Ice Harbor Dam, 2008

Report of the National Marine Fisheries Service to the U.S. Army Corps of Engineers, Walla Walla, Washington</p

Passage behavior and survival of radio-tagged yearling Chinook salmon and steelhead at Ice Harbor Dam, 2006

Report to the US Army Corps of Engineers, Walla Walla, Washington</p

Success and succession in species and ecosystem recoveries: kelp forest community dynamics following decades of sea otter re-establishment

The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One of the most iconic examples of this potential comes from keystone predation by sea otters in nearshore habitats of the Northeast Pacific. On the outer coast of Washington state, USA, a population of sea otters re-introduced in 1969-1970 exhibited a more than 10-fold increase during the 1980s and 1990s. This population increase led to a pronounced decline in sea otter prey, particularly kelp-grazing sea urchins. Here we show that the reduction in invertebrate prey coincided with an expansion of kelp beds coastwide until the turn of the century. However, while sea otter and kelp population growth rates were positively correlated prior to 2000, this association diminished substantially in the last 15+ years. A recent 2015 survey of benthic invertebrates shows that sea otter prey have continued to decline as the sea otter population has continued to expand, but kelp abundance is not closely related to these trends. However, variability in kelp abundance has declined in the most recent 15 years of the time series. Altogether these results suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now other factors may be as or more important in influencing community dynamics. Thus, the role of sea otter predation may be context-dependent with shifting environmental conditions strongly affecting their utility in ecosystem restoration