Salmon Life Cycle
Salmon hatch in freshwater from eggs laid in the gravel beds of rivers and streams (and in some cases along lake shorelines). Except for steelhead and cutthroat, adults die after spawning a single time. Upon hatching, juveniles spend from hours to years in the freshwater environment before migrating to the sea to grow to adulthood. Oceanic migrations typically take them northward along the continental shelf as many as thousands of miles, often into the Gulf of Alaska and beyond. On reaching maturity, they migrate from the ocean back to the rivers and streams of their birth to spawn.

Range and Adaptation
All Pacific salmon are members of the genus Oncorhynchus, meaning "bent snout". Their home streams range from southern California to northern Alaska and from Siberia southward to Hokkaido, Japan. Salmon are well-adapted to gravel-bedded rivers and streams with clear, well-oxygenated waters that remain cold throughout the year (42-58o F). Gravels must be relatively free from silts and fine sands to allow free flow of water and oxygen to eggs deposited in the inter-gravel spaces. Various salmon species assort themselves by stream size, gravel size, flow and depth of water, and timing of return. Watershed-specific variations in these characteristics have produced populations that are "fitted" to these environments and that differ in subtle ways from adjacent populations. This local adaptation is a fundamental characteristic of salmon. Seven species are represented in the waters of King County and Puget Sound: Chinook; coho; pink; chum; sockeye; steelhead/rainbow; and cutthroat.

Onchorynchus tshawytscha—Chinook, or "King" Salmon
In King County chinook are found in the Snoqualmie, Cedar, Green and White river systems. Some basic facts about Chinook salmon include:

• Chinook are the largest of all Pacific salmon, averaging 36 inches in length and 22 pounds in weight; they are also the least abundant species.
• Chinook spawn mostly in large streams and are found in all major watersheds in Puget Sound. The largest runs in the Sound are on the Skagit, Stillaguamish and Snohomish (including the Snoqualmie/Skykomish) rivers. Chinook are also present in smaller tributaries, including Bear Creek, North Creek and Newaukum Creek in King County. Virtually all Puget Sound populations are far below what are believed to be their historic numbers; most have declined from 18% to more than 90% since the 1960s.
• There are spring, summer and fall runs of Chinook in Puget Sound; fall runs, which migrate up parent streams from late July through September, tend to be the most abundant.
• Adult Chinook die within 2-5 days of spawning; their eggs hatch in about 60 days. Newly hatched salmon, called "alevins," remain in the gravel for about 3 weeks; upon emerging, the "fry" or "parr" remain in freshwater for about 3-6 months (in the Lake Washington system, some may reside in the lake for 2-3 years), feeding on stream and terrestrial insects. Now called "smolts," they migrate downstream to Puget Sound, where they feed and grow for several weeks to over a year; they then migrate northward to the Gulf of Alaska, where they feed on small fishes and krill for 2-4 years before migrating homeward to spawn.