Lake Washington, the largest lake in King County and the second largest natural lake in Washington State, is a significant freshwater body in the Pacific Northwest. Located adjacent to Seattle, it borders several cities and encompasses Mercer Island. The lake connects to Puget Sound via the Lake Washington Ship Canal, a passage constructed in 1916 that also lowered the lake’s water level. It serves as an important ecological system within its developed watershed.
Native Fish Species of Lake Washington
Lake Washington is home to several native fish species, particularly various salmonids. Sockeye Salmon are notable, with most returning to the Cedar River to spawn, though some also use other tributaries and the lake’s eastern shoreline. Juvenile sockeye remain in Lake Washington for about a year before migrating to the ocean. Adult sockeye enter the lake from late May to late August, holding in deeper, cooler waters before spawning from September to January.
Coho Salmon, also known as silver salmon, are present in the Lake Washington basin and its tributaries. They spend their first 18 months rearing in freshwater streams before migrating to the ocean. Adults return to spawn in their natal streams from late October into late December.
Chinook Salmon, the largest Pacific salmon species, are listed as threatened under the Endangered Species Act. Juvenile Chinook utilize shallow, nearshore areas of Lake Washington for feeding and growth. They migrate from the Cedar River into Lake Washington and eventually to Puget Sound.
Coastal Cutthroat Trout are another native salmonid found in Lake Washington. These trout prefer moderately deep, cool lakes with ample shallows and vegetation for food production. They can be identified by red slash marks under their lower jaw and numerous irregular spots.
The Northern Pikeminnow, a large predatory minnow, is also native to the region and inhabits a wide variety of lake and river habitats. They are known to consume other fish, including juvenile salmonids. Peamouth, a schooling minnow averaging about a foot in length, are common in the shallow, weedy zones of lakes and rivers. They spawn in streams connected to the lake before returning to the lake.
Introduced Fish Species of Lake Washington
Lake Washington also contains several introduced fish species. Smallmouth Bass, a popular sport fish, were first introduced to Lake Washington in 1925. They prefer cooler water and are found in rocky areas, near stumps, or on sandy bottoms. These predatory fish consume insects, crayfish, and other fish.
Largemouth Bass, another predatory species, also inhabit Lake Washington and prefer areas with gentle-sloping banks and aquatic vegetation. Yellow Perch are widely established in the lake, known for their distinctive vertical barring and schooling behavior. Brown Bullhead, a species of catfish, are also found in Lake Washington, inhabiting soft-bottomed areas in lakes and slow-moving rivers.
Walleye, a popular sport fish, were introduced to Washington State in the 1950s and their range has expanded to include Lake Washington. They prefer cooler, deeper waters during warmer months and move to shallower areas for spawning in spring. Walleye are recognized by their large, opaque-white eyes, an adaptation for low-light conditions.
Conservation and Management Efforts
Conservation and management efforts in Lake Washington focus on protecting fish populations and maintaining aquatic health. These initiatives involve monitoring water quality, which has significantly improved since sewage diversion efforts in the 1960s. Water clarity and chemical parameters have stabilized, benefiting the lake’s ecosystem.
Habitat restoration is an important component, especially for native salmonids like Chinook Salmon. Projects involve removing structures, placing sand and gravel to create suitable shallow-water habitats, and planting native vegetation along shorelines. Efforts also include improving fish passage through barriers and reconnecting waterways to their natural floodplains. General fishing regulations are in place to manage fish populations, ensuring sustainable recreational opportunities while supporting ecosystem balance.