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.
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| 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.
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