The U. S. Fish and Wildlife Service is working with the City of Portland Bureau of Environmental Services to evaluate the success of aquatic habitat improvements in Tryon Creek. In 2010, the City of Portland completed a 900-foot off-channel aquatic habitat enhancement along the Willamette River. Habitat improvements included floodplain connectivity, removal of invasive species, and installation of root wads and boulders.
In 2012, the U. S. Fish and Wildlife Service began an intensive monitoring program to assess community, relative abundance, and temporal use by fish in the improved area. Sampling occurred monthly throughout the year and weekly in the spring, sampling will continue in July 2014 at the same frequency. Backpack electrofishing and seining is used to sample from the confluence to the Oregon State Highway 43 culvert. All captured fish are identified, checked for external markings, measured, and tagged with a passive integrated transponder (PIT) tag. Genetic samples collected from salmonids are transferred to the City of Portland. To determine temporal fish use of the confluence habitat, two PIT tag antennas are installed at the mouth of Tryon Creek. All PIT tagged fish moving over or through these antennas have the opportunity to be detected and identified before entering or exiting the Willamette River.
|Sampling the mouth of Tryon Creek|
Resident fish such as adult and juvenile cutthroat trout, rainbow trout, and hybrids of the two were identified in the confluence habitat along with outmigrating juvenile steelhead, Chinook, and coho salmon. Native fish were more abundant than nonnative fish and coho juveniles were the most abundant species observed. Coho and Chinook were detected emigrating after an average 37-44 days suggesting the habitat serves as a refuge for outmigrating juvenile salmon from elsewhere in the Willamette River basin. PIT tagged Chinook and coho salmon (originating from upstream locations in the upper Willamette River basin and Eagle Creek) utilized the Tryon Creek confluence as part of their migration.
The Tryon Creek Confluence Habitat Enhancement Project improves aquatic habitat in the lower Willamette floodplain and provides refuge for native fish species. Information collected from this assessment will aid the City of Portland in determining if the project is meeting its goals, gauging if the site is achieving desired function over time, and improving the design of future projects.
This project is relatively small compared to the Willamette watershed overall, however, the combined efforts of habitat improvement and fish monitoring lead to a larger product. This collaboration improves the design of future projects benefitting the entire Willamette River and supports the U. S. Fish and Wildlife Service’s mission to work with others to conserve, protect and enhance fish, wildlife, and plants and their habitats for the continuing benefit of the American people.
For additional information, please see this factsheet from the City of Portland:
Submitted by Brook Silver