(
Acipenser transmontanus), almost long, caught in 1998 in the Russian River's "Hacienda Hole" in
Guerneville, California Fish populations The river provides wildlife habitat including warm and cold freshwater habitat for fish migration and spawning. These were presumably
white sturgeon (
Acipenser transmontanus), the largest freshwater fish in the United States. Khlebnikov stated in his "1820 Travel Notes": "Mr.
Kuskov had sent two
baidarkas to the Slavyanka River to catch sturgeon, and they returned today with ten fish... the largest one exceeding two arshins (4.67 feet) long". Moyle's
Inland Fishes of California states that there were historic runs of white, but not green, sturgeon in the Russian River. The Russian River is the largest river in the Central California Coast
steelhead trout (
Oncorhynchus mykiss)
distinct population segment. Natural waterfalls and the two major dams, Warm Springs (built in 1982) and Coyote (built in 1959), have isolated
anadromous steelhead from its non-oceangoing rainbow trout form above the impassable barriers. Recent genetic studies on steelhead collected at 20 different sites both above and below passage barriers in the watershed found that despite the fact that 30 million hatchery trout were stocked in the river from 1911 to 1925, the steelhead remain of native and not hatchery stock. Until recently, most reviews indicated that
Chinook salmon (
Oncorhynchus tshawytscha) were always scarce on the Russian River. However, in 2007, the
Sonoma County Water Agency completed a comprehensive re-evaluation of historical records, coupled with a five-year monitoring program using underwater cameras at two fish ladders just north of
Forestville. They found that Chinook salmon always were, and still are, "a relatively abundant, widely distributed, and naturally self-sustaining population". The authors found historic information dating to 1881 suggesting the presence of an ancestral population, and their genetic analysis found the Chinook both above and below barriers to fish passage to be of native, and not hatchery stock. In 2001 the
Coho salmon (
Oncorhynchus kisutch) had dwindled to less than four returning spawners per year. These low numbers were the catalyst for the Russian River Coho Salmon Captive Broodstock Program, a recovery effort in which offspring from hatchery-reared adults are released into the river system. In 2011, biologists estimate that more than 190 adult coho may have returned to the Russian River watershed, beginning with early storms in October and peaking in December. High priority tributaries for restoration of stream flows and habitat for Coho include
Dutch Bill, Grape,
Green Valley,
Mark West and
Mill Creeks. A 2010 survey by the Sonoma County Water Agency also examined populations of the
Russian River tule perch, the only species of fish endemic to the watershed of the river. It found populations of the fish, currently considered a
California Department of Fish and Game (CDFG) Species of Special Concern, in 94% of the river
mainstem, through a combination of historical statistics and empirical surveying at trap sites. Tule perch accounted for 2.9% to 9.5% of all fish observed in the upper portion of the river, with their presence largely confined to areas of riparian vegetation; however, specimens were also observed in the confluence of the river with Willow Creek, a brackish estuary area, indicating that the species may take advantage of freshwater
microhabitats. However, the
Russian-American Company's
Ivan Kuskov sailed into
Bodega Bay in 1809 on the
Kodiak and, after exploring 50 miles of the Russian River, returned to
Novo Arkhangelsk, Alaska (Sitka), with beaver skins and over 2,000
sea otter (
Enhydra lutris) pelts. The Russians' stated reason for establishing a settlement in
Alta California was, "The rich, fertile soil [and] the abundance of seal, otter and beaver were the principal factors which favored this colonization." An 1816 report by the Russian-American Company's Board of Directors said that it was establishing a settlement to introduce agriculture. Before establishing a southern colony at
Fort Ross, the Russian-American Company contracted with American ships beginning in 1806, providing them with
Aleuts and their
baidarkas (kayaks) to hunt otter on the coast of Spanish California. The
Hudson's Bay Company's
Alexander R. McLeod reported in 1829, "The Country to the northward of Bodega is said to be rich in Beaver and no encouragement given to the Indians to hunt." The fur trapper
Ewing Young led an expedition up
Putah Creek to
Clear Lake and onward to the
Mendocino County Coast in March of 1833. James Weeks, a member of Young's 1833 fur brigade, wrote: "They broke up all the beaver lodges on the lake, I believe the finest and largest beaver we caught there, we arrived at the Russian River and pitched camp sent out, trappers found signs set traps caught beavers..." This historical observer record is consistent with the
Southern Pomo, who inhabited the lower half of the Russian River, having a word for beaver, ''ṱ'ek:e
, and beavers in their "Coyote Stories". In 1881 the Sacramento Daily Union'' newspaper reported "Beavers are being trapped near Healdsburg", placing them again on the Russian River.
Toxic cyanobacteria After the death of a household dog which had been exposed to the river's waters in 2015, a toxicology investigation identified the cause to be
anatoxin-a, a highly potent neurotoxin produced by certain freshwater
cyanobacteria. The compound induces a state of paralysis by binding to
acetylcholine receptors in muscle nerves, and is known due to its rapid manifestation of symptoms as the "Very Fast Death Factor". The species which produce the compound tend to occur in nutrient-poor freshwater ecosystems, including rivers, and grow as filamentous mats on surfaces along the
benthic zone of a river. Previous reports have occurred in New Zealand, Northern California and, more recently, Utah. A study by Conklin et al, examining samples collected from the river in October of 2015, attempted to isolate species of anatoxin-producing cyanobacteria. Analysis of the three collected benthic mats resulted in the discovery of the new species
Microcoleus anatoxicus, in the genus
Microcoleus, which contains several related and similarly toxic species found in Northern California and New Zealand bodies of freshwater. A further study published in 2025 examined the relationship between toxigenicity and growth rates in anatoxin-producing and nonproducing
Microcoleus samples collected from Northern California rivers. The results identified faster growth rates in toxin-producing samples of
Microcoleus anatoxicus, the newly identified species, particularly in nutrient-rich environments. This conclusion reverses previous research indicating a contrary effect and implies a possible impact on growth rates from nutrition levels, particularly inorganic nitrogen. ==Russian River Valley==