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

counter to the main stream; from these, they can make forays up into surface currents to
take drifting food (Kalleberg 1958). Juveniles rear in freshwater from one to four years,
then smolt and migrate to the ocean in March and April (Barnhart 1986). Winter
steelhead juveniles generally smolt after two years in freshwater (Busby, Wainwright et
al. 1996). Juvenile steelhead tend to migrate directly offshore during their first summer
from whatever point they enter the ocean rather than migrating along the coastal belt as
salmon do. During the fall and winter, juveniles move southward and eastward (Hartt
and Dell 1986) op. cit. (Nickelsen, Nicholas et al. 1992). Steelhead typically reside in
marine waters for two or three years prior to returning to their natal stream to spawn as
four or five year olds. Juvenile salmonids rely on a variety of non-main channel habitats
that are critical to rearing. All listed salmonids use shallow, low flow habitats at some
point in their life cycle. Examples of off-channel habitat include alcoves, channel edge
sloughs, overflow channels, backwaters, terrace tributaries, off-channel dredge ponds,
and braids (Anderson 1999; Swift III 1979).
Status and Trends
Steelhead, like the other salmon discussed previously, survive only in aquatic ecosystems
and, therefore, depend on the quantity and quality of those aquatic systems. Steelhead,
like the other salmon NMFS has listed, have declined under the combined effects of
overharvests in fisheries; competition from fish raised in hatcheries and native and nonnative
exotic species; dams that block their migrations and alter river hydrology; gravel
mining that impedes their migration and alters the hydrogeomorphology of the rivers and
streams that support juveniles; water diversions that deplete water levels in rivers and
streams; destruction or degradation of riparian habitat that increase water temperatures in
rivers and streams sufficient to reduce the survival of juvenile chum salmon; and land use
practices (logging, agriculture, urbanization) that destroy wetland and riparian
ecosystems. These same activities and features introduce sediment, nutrients, biocides,
metals, and other pollutants into surface and ground water and degrade water quality in
the freshwater, estuarine, and coastal ecosystems throughout the Pacific Northwest.
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