EPA's Vessel General Permit and Small Vessel General

natural and hatchery fish with an intact adipose fin, but not to listed hatchery fish that have had
their adipose fin removed prior to release into the wild. The amended June 2005 4(d) rule
applies to the South-Central California steelhead DPS.
Southern California Steelhead
Distribution and Description of the Listed Species
The Southern California steelhead DPS includes all naturally spawned populations of steelhead
in streams from the Santa Maria River, San Luis Obispo County, California (inclusive) to the
U.S.-Mexico border. Artificially propagated steelhead that reside within the historical
geographic range of this DPS are not included in the listing.
A comprehensive assessment of the distribution of steelhead within the Southern California DPS
indicates that steelhead occur in most of the coastal basins (Boughton and Fish 2003 in Good et
al., 2005). Major watersheds occupied by steelhead in this DPS include the Santa Maria, Santa
Ynez, Ventura, Santa Clara rivers. Smaller watersheds that support steelhead include the Los
Angeles, San Gabriel, San Luis Rey and Sweetwater rivers, and San Juan and San Mateo creeks.
Significant portions of several upper watersheds are contained with four national forests (Los
Padres, Angeles, Cleveland, and San Bernardino National Forests), whereas coastal and inland
valleys are dominated by urban development, with the Los Angeles basin being the most
expansive and densest urban area in the DPS. Populations within the southernmost portion of the
DPS (San Juan Creek, San Luis Rey River and San Mateo Creek) are separated from the
northernmost populations by about 80 miles.
Status and Trends
NMFS listed Southern California steelhead as endangered in 1997 (62 FR 43937), and
reaffirmed their status as endangered on January 5, 2006 (71 FR 834). Historical and recent data
is generally lacking for Southern California steelhead, making a general assessment of their
status difficult. The historical run size estimate for the entire DPS was between 32,000-46,000
steelhead, but this estimate omits the Santa Maria system and basins south of Malibu Creek
(Busby et al. 1996). Estimates for the Santa Ynez River Basin, probably the largest run
historically, range from 13,000 to 30,000 spawners, although this number may underestimate the
steelhead abundance in the basin prior to the construction of Juncal and Gibraltar dams (Busby et
al., 1996; Good et al., 2005). No recent data are available for steelhead in the Santa Ynez basin,
and most of the historical spawning habitat was blocked by Bradbury and Gibraltar dams.
Steelhead and rainbow trout are known to occur in streams downstream of Bradbury Dam, but no
estimates of abundance or trends are available. Similarly, Twitchell Dam in the Santa Maria
River, and Casitas Dam on Coyote Creek and Matilija Dam on Matilija Creek block access to
significant portions of historical spawning and rearing habitat, and alter the hydrology of the
basins. A fish ladder and counting trap at the Vern Freeman Diversion Dam on the Santa Clara
River is thought to be dysfunctional (Good et al. 2005). In general run sizes in river systems
within the DPS are believed to range between less than five anadromous adults per year, to less
than 100 anadromous adults per year. An estimated 26-52% of historically occupied basins are
believed to still contain some steelhead, and about 30% are believed vacant, extirpated or nearly
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