Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

may affect steelhead migration patterns. For example, some populations of coho and
Chinook salmon, at least historically, remained within Puget Sound and did not migrate
to the Pacific Ocean. Even when Puget Sound steelhead migrate to the high seas, they
may spend considerable time as juveniles or adults in the protected marine environment
of Puget Sound. This is a feature not readily accessible to steelhead from other areas of
the Pacific Northwest. The species is primarily composed of winter steelhead but
includes several stocks of summer steelhead, usually in subbasins of large river systems
and above seasonal hydrologic barriers.
Life History
Life history attributes of Puget Sound steelhead (migration and spawn timing, smolt age,
ocean age, and total age at first spawning) appear similar to those of other west coast
steelhead. Ocean age for Puget Sound summer steelhead varies among populations.
Status and Trends
Puget Sound steelhead were listed as a threatened species on May 11, 2007 (72 FR
26722). Run size for this DPS, was calculated in the early 1980s at about 100,000
winter-run fish and 20,000 summer-run fish. It is unclear what portion were hatchery
fish. However, a combined estimate with coastal steelhead suggested that roughly 70%
of steelhead in ocean runs were of hatchery origin. The percentage in escapement to
spawning grounds would be substantially lower due to differential harvest and hatchery
rack returns. By the 1990s, total run size for four major stocks exceeded 45,000, roughly
half of which was natural escapement.
Nehlsen et al. (1991) identified nine Puget Sound steelhead stocks at some degree of risk
or concern. The WDFW et al. (1993) estimated that 31 of 53 stocks were of native origin
and predominantly natural production. The WDFW assessment of the status of these 31
stocks was 11 healthy, three depressed, one critical, and 16 of unknown status. Their
assessment of the status of the remaining (not native/natural) stocks was three healthy, 11
depressed, and eight of unknown status.
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