Sockeye salmon typically spawn in streams that flow into large lakes
systems to allow juvenile sockeye to rear for a year or more in a deepwater
lake environment before migrating to sea. Prior to the 1930s, Lake Washington
was famous for its large populations of kokanee (the freshwater form of
the sockeye), but sea-run sockeye salmon were thought to be absent. In
the year 1916, the ship canal was opened to serve as a new outlet for
Lake Washington and to provide the water needed to operate the just completed
Hiram M. Chittenden Locks at Ballard. This combined the extensive spawning
grounds of the Cedar River with a large lake rearing environment, provided
an opportunity to develop a major sockeye salmon population in the waters
of southern Puget Sound.
Sockeye were introduced into the Lake Washington watershed in 1935 (and
subsequent years) from the Baker River. The first documented adult returns
to Lake Washington were in 1940 when 9,099 sockeye were counted at the
Washington Department of Fisheries hatchery on Issaquah Creek. The run
gradually increased, and in 1970 an escapement goal of 350,000 spawners
was adopted and in 1971 the first directed fisheries occurred. Since then,
sockeye returns have significantly fluctuated (see figure below) despite
supplementation efforts and harvest restrictions, theoretically due to
freshwater and ocean survival constraints, and because of an increased
frequency in damaging winter floods.
Genetic studies of the Cedar River and Issaquah Creek sockeye show that
the present run is genetically similar to the Baker sockeye stock. Recent
genetic studies of northern Lake Washington tributary sockeye and beach
spawning sockeye have revealed that these groups of sockeye is also related
to the introduced Baker stock, suggesting that all current sockeye populations
in the system are derived from the introduced fish.
