Project: Research, Monitoring, and Evaluation of Caspian Terns and Double-crested Cormorants Relative to Their Impact on Salmonid Smolts in the Columbia River Estuary
Client: Bonneville Power Administration & USACE - Portland District
Year: 1997 – 2019
Location: Columbia River EstuaryObjectives of these studies were to (1) assess the relative impacts of avian predators on smolt survival in the Columbia River estuary, (2) work with resources managers to develop management initiatives to reduce those impacts, (3) monitor and evaluate the efficacy of implemented management actions, and (4) provide analytical and technical support at a program level.
Study results indicated that avian predation was a factor limiting the recovery of some salmonid populations from the Columbia River basin that are listed under the U.S. Endangered Species Act. In recent years, the large breeding colonies of Caspian terns and double-crested cormorants in the Columbia River estuary on East Sand Island consumed more than 20 million smolts annually. Management is underway to reduce the smolt impacts of Caspian terns by reducing the amount of available nesting habitat for terns in the estuary and creating alternative nesting habitat elsewhere (i.e., outside the basin). This plan has been successful in reducing both Caspian tern colony size and smolt impacts in the Columbia River estuary. A separate management plan to reduce the impacts of double-crested cormorants nesting on East Sand Island on the survival of juvenile salmonids from the Columbia Basin was initiated in 2015.
Project was conducted with Oregon State University and required close coordination and collaboration with BPA and the Corps, as well as multiple Federal, State, and Tribal stakeholders.