EPA's Vessel General Permit and Small Vessel General

estuaries and in fresh water coho salmon are significant predators of Chinook, pink, and chum
salmon, as well as aquatic and terrestrial insects. Smaller fish, such as fry, eat chironomids,
plecoptera and other larval insects, and typically use visual cues to find their prey.
Threats
Natural Threats. Coho salmon, like other salmon, are exposed to high rates of natural predation
at each life stage. Most mortality, however, occurs in the freshwater life stages. Winter
mortality may be significant for coho salmon because they overwinter in fresh water, where they
can be swept downstream from freshets or eaten by raccoon, cutthroat trout or other small
animals. Once coho reach the ocean, survival is high (Sandercock 1991).
Anthropogenic Threats. Coho salmon have declined under the combined effects of overharvests
in fisheries; competition from fish raised in hatcheries and native and non-native exotic species;
dams that block their migrations and alter river hydrology; gravel mining that impedes their
migration and alters the dynamics (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 coho salmon; and land use practices (logging, agriculture,
urbanization) that destroy wetland and riparian ecosystems while introducing sediment, nutrients,
biocides, metals, and other pollutants into surface and ground water and degrade water quality in
the fresh water, estuarine, and coastal ecosystems throughout the species’ range. These threats
for are summarized in detail under Chinook salmon.
Central California Coast Coho Salmon
Distribution and Description of the Listed Species
The Central California Coast coho salmon ESU extends from Punta Gorda in northern California
south to and including the San Lorenzo River in central California (Sandercock 1991). The ESU
includes all naturally spawned populations of coho salmon from Punta Gorda in northern
California south to and including the San Lorenzo River in central California, as well as
populations in tributaries to San Francisco Bay, excluding the Sacramento-San Joaquin River
system. Four artificial propagation programs are part of the Central California Coast coho
salmon ESU.
Coho salmon in this ESU enter rivers to spawn very late (peaking in January), with little time
spent in fresh water between river entry and spawning. This compressed adult freshwater
residency appears to coincide with the single, brief peak of river flow characteristic of this
region.
Status and Trends
NMFS originally listed the central California coast coho salmon ESU as threatened on October
31, 1996 (61 FR 56138) and later reclassified their status to endangered June 28, 2005 (70 FR
37160). Information on the abundance and productivity trends for the naturally spawning
component of the central California coast coho ESU is extremely limited. There are no longterm
time series of spawner abundance for individual river systems. Historical estimated
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