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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

MAILING ADDRESS: 1120 SW 5th Ave, Room 1000, Portland, OR 97204

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Biological Communities

Aquatic Biology

Tryon Creek and its tributaries provided important habitat for various fish and other aquatic species before the turn of the century. Over the past decades, however, many major modifications have been made in the watershed and have significantly affected fish and aquatic habitat and passage (BES 1997; Pacific Habitat Services 1997; PSU and Metro 1995).


Tryon Creek is entirely free-flowing within the Tryon Creek State Natural Area, where it seems to provide the best available habitat in the watershed. However, the Highway 43 crossing near the creek’s confluence and the Boones Ferry Road crossing appear to restrict fish movement. Most of the fish populations in the watershed are tolerant resident species.


To date, information on macroinvertebrates in Tryon Creek and its tributaries is limited to observations by Oregon Department of Fish and Wildlife fish biologists as part of their work to assess fish and fish habitat. These observations have consistently pointed to unsuccessful spawning of salmonids and the absence of aquatic insects. In one report, the absence of aquatic insects was theoretically linked to some form of water quality problem.


The Tryon Creek Watershed provides shelter to several wildlife species, most of which are nocturnal (BES 1997; Pacific Habitat Services 1997; PSU 1995). Black bear, cougar, and Roosevelt elk existed before development. Today, the watershed is still home to smaller, more adaptive mammals. The green space of the West Hills and the forested refuge of Tryon Creek State Natural Area provide the primary habitat for the wildlife species in the watershed. The most common mammals are bats, beavers, blacktail deer, chipmunks, coyotes, flying squirrels, mice, moles, opossums, rabbits, raccoons, red foxes, shrews, skunks, and squirrels.

More than 60 species of birds reside within the watershed for at least a portion of the year. Birds are attracted to the variety of habitats found within the watershed’s evergreen forests, deciduous woods, stream corridors, fringes of open fields, and numerous backyard birdhouses. Some of the birds found in the Tryon Creek Watershed include chickadees, Cooper's hawks, ducks, great horned owls, great blue herons, hummingbirds, jays, juncos, kingfishers, nuthatches, robins, sparrows, thrushes, towhees, warblers, waxwings, western screech owls, woodpeckers, and wrens (BES 1997; Pacific Habitat Services 1997; PSU 1995).