of Tualatin River National Wildlife Refuge
Western Brook Lamprey -USFWS - 512x289

Numerous fish species have been noted using the waters in and adjacent to refuge lands.

Native Fish

Native species that have been recorded in surveys following flood events include western brook lamprey, three-spined stickleback, and sculpin.

Native fish species such as lampreys, sculpin, and three-spined sticklebacks have also been recorded in refuge waters and are an important part of the aquatic community. The presence of lampreys is a good indicator of water quality as they will not persist in poor-quality habitats. Three-spined sticklebacks, which were numerous in our sampling, may be beneficial in removing mosquito larvae from slow-moving waterways.

Non-native Fish

Non-native species recorded in surveys include carp, mosquito fish, and bluegill. From 1999 to 2001, the Oregon Department of Fish and Wildlife conducted fish surveys in the Tualatin River Basin and recorded 16 species of fish from seven families. The survey noted that only 0.16 percent of the total sample were non-native fish.

Non-native fish such as carp, bass, catfish, and sunfishes are disruptive to and can outcompete native species. Carp uproot and consume submergent vegetation important to native species and cause turbidity, thus inhibiting further growth of vegetation. Bass, catfish, and sunfishes directly consume native species, such as red-legged frogs, and also indirectly affect native species by consuming food such as invertebrates that native species forage upon.

Facts About Fish