Seafood Watch

Seafood Watch® Wild Pacific Salmon Report October 8, 2010
been even more severe, and read like an encyclopedia of habitat destruction: an 85% loss of
coastal redwood (Sequoia sempervirens) forests, an 89% loss of Central Valley riparian forests, a
90-98% decline of Sacramento River riparian and bottomland forests, a 99.9% loss of Central
Valley riparian oak forest, a 94% loss of inland wetlands (including the Central Valley), a 69%
loss of tule marsh, a 66-88% loss of Central Valley vernal pools, and a 62% loss of salt marshes
(compiled by: (Noss et al. 1995)). Notably, Washington and Oregon both lost over a third of
their wetlands between 1780 and 1980, and 91% of California’s wetlands have been drained or
otherwise destroyed (Noss et al. 1995). In contrast, just 0.1% of Alaska’s wetlands were lost over
that period. Indeed, Alaska is the only region of the United States without endangered
ecosystems. While 11 percent of Alaska's original coastal temperate rainforests have been
logged, the percentage still compares favorably against the 75-90% losses in California, Oregon,
and Washington.
Pollution can also be detrimental to salmon habitat. In many coastal regions, agricultural and
urban run-off as well as atmospheric deposition have significantly reduced freshwater, estuarine,
and coastal water quality (Boesch et al. 2001). Pollution can reduce the viability of salmon
embryos, though the extent of these effects has not been quantified on West Coast salmon.
Typically, agricultural chemicals such as pesticides are found in freshwater habitats at levels well
below thresholds for acute mortality; however, pesticides can still cause sublethal effects that
could ultimately cause ecological mortality. Potential harms include impaired swimming ability,
reduced sense of smell, and disrupted immune and hormonal systems. The lack of data on the
sublethal toxicity of pesticides for salmonids has been described as a “key uncertainty” for the
recovery prospects of many ESUs (Sandahl et al. 2004). In 2002, a court order prohibited the
application of 30 types of pesticides within close proximity to salmon waters in California,
Oregon, and Washington.
As with dams, this wide array of damages to salmon habitat appears to have significantly
reduced both the quantity and quality of available Pacific salmon spawning habitat in the
southern half of their traditional range. Alaskan habitat appears to have remained relatively
robust during this period. Pollution is likewise less prominent of an issue in Alaska. While the
Exxon Valdez oil spill received considerable attention for the detrimental effects it caused to
salmon and other animals, current research indicates that spawning habitat has largely recovered
from the spill 15 years ago (Carls et al. 2004).
Introduced Species
In addition to physical alterations, biological alterations to habitat can have substantial effects on
salmon. In particular, introduced species can represent a subtler degradation of habitat. For
example, over the past 150 years, over 20 species of fish have been introduced into the Columbia
River Basin, several of which have become established. Currently, one fifth of the number of fish
found in designated “wilderness area” streams in the basin are introduced species (Levin et al.
2002). In many areas, introduced species are even more pervasive. For example, in a 1993
survey of nearly one thousand samples (boat electrofishing, gillnets, and hoopnets) in the
southern Sacramento-San Joaquin Delta, introduced species represented 99% of the total number
of fish collected (Feyrer and Healey 2002).
In many areas, these introductions have had significant detrimental effects on salmon. One of the
most detrimental introductions is brook trout (Salvelinus fontinalis), the most abundant
introduced species in threatened spring and summer-run Chinook spawning habitat in the
23