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There are approximately 50 species of freshwater fish in King County, and 20 of those are introduced. The native Salmonids—the Pacific salmon, char and whitefishes—are the best known fishes of King County waters. They are discussed below as well as at length elsewhere on King County's website.

The other freshwater fishes native to King County waters include the Western brook lamprey, a stream-dwelling, diminutive cousin of the larger Pacific lamprey; white sturgeon, the largest native fish in King County waters and only rarely observed in Lake Washington; longfin smelt; six members of the family Cyprinidae (minnows), including three species of dace, one species of shiner, a peamouth chub, and the northern pikeminnow; two species of sucker; the ubiquitous threespine stickleback; six species of sculpin; and the starry flounder, a flatfish of brackish river mouths.

Taxonomic information on these and other Washington fishes can be found on these websites:

  • Freshwater Fishes of Washington, a list generated by the Slater Museum of Natural History, University of Puget Sound, using Inland Fishes of Washington, Wydoski, R. S., and R. R. Whitney. 2003. Second Edition. Univ. Washington Press, Seattle.
  • A Key to the Fishes of Puget Sound, presented by the Burke Museum. This key features marine and freshwater species.

A few freshwater species highlighted

Peamouth ("peamouth chub" or "peamouth minnows") are in the minnow and carp family and grow to about a foot long. Thousands of peamouth move from Lake Washington to its tributaries every spring in April or May to spawn. They remain there for less than two days before heading back to the lake. And if you happen to look into a stream when they are spawning, you’ll be shocked at how many fish there are. City of Bellevue's Stream Team actually has a "Peamouth Patrol," wherein volunteers count them each spring!

peamouthmalefemalepair
Threespine stickleback are a small fish found in big and small lakes and streams in King County as well as in a lot of other places around the Northern Hemisphere. They are circumpolar in Arctic and temperate regions. Occasionally, there will be  die-offs of this plentiful fish in Lake Washington; fear not, it is normal. And if you google threespine stickleback? You will see lots of articles about how they provide keys to information about genetics and evolution!
stickleback

Salmon and Trout

Many of our salmon and trout species are anadromous -- meaning they are born in our streams, they migrate to the ocean to feed and grow into mature adults, then they return to their natal stream to spawn. These fish, therefore, are both freshwater and marine species, depending on the time of year.

Of this group, the species of Pacific salmon, members of the genus Oncorhynchus, are by far the most important and iconic. There are 7 species of the genus Oncorhynchus that inhabit King County waters: Chinook or king salmon, the largest of the group; chum or dog salmon; sockeye salmon; coho salmon; pink salmon; steelhead trout; and Coastal cutthroat trout, an inhabitant of even the smallest streams in the county.

Regulated Fish

In addition to many of the salmonids, some freshwater species are also protected.

Pygmy Whitefish. The pygmy whitefish is a State Sensitive species that spawns in cold fast-flowing mountain streams that flow into cool lakes, where they rear. Their only population in King County is in the Cedar River above Chester Morse Lake. Too little is known about this population to know how it is doing relative to pre-logging conditions. However, the vast majority of this watershed, which was historically logged, will no longer be logged, and as forest conditions mature, it is assumed the stream conditions will remain the same or improve, and likely the same will be true for pygmy whitefish. View the City's webpage about Pygmy Whitefish for great information about this species. View the Washington State Status Report for the Pygmy Whitefish, Sept. 1998.

Olympic Mudminnow. The Olympic mudminnow is a State Sensitive species that is most often found in slow-moving streams and wetlands. King County is out of its range; however, this species has been documented in certain streams and wetland ponds in the county, but it is thought that the presence of these individuals is the result of introductions of the fish by people, and not because of a natural range extension. View a USGS fact sheet on Olympic Mudminnows. View the Washington State Status Report for the Olympic Mudminnow, October 1999.