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NATURAL HISTORY

COLORADO RIVER CUTTHROAT TROUT} Oncorhynchus clarki pleuriticus
FAMILY: Salmonidae

DESCRIPTION: On average, Colorado River cutthroat measure around eight inches long and weigh no more than five pounds, though lake-bound individuals can grow considerably larger. Typically, the trout are brown or olive in color, with distinctive black spots. During spawning season, the distinctive red marking behind the fish’s gills becomes more pronounced and occasionally extends onto the belly and body.

HABITAT: Like most trout, the Colorado River cutthroat requires clear, cold, naturally flowing water with ample pools, stream cover, and low-sediment gravel beds.
 
RANGE: While the Colorado River cutthroat was historically plentiful in the Colorado River drainage in Wyoming, Colorado, Utah, Arizona, and New Mexico, today it is found in less than 5 percent of this former range.

MIGRATION: Cutthroat trout do not migrate, though they will travel from their birthplace to form their own territories.

BREEDING:  Cutthroat become sexually mature when they are two or three years old, spawning in spring when river levels rise. Eggs are deposited in nests built in streambed gravel and typically hatch within four to five weeks.

LIFE CYCLE: The average lifespan for a cutthroat is between six and eight years.

FEEDING: Cutthroat trout are visual hunters that feed on both aquatic and flying insects. Very large trout may prey on other fish.

THREATS: This fish is most seriously threatened by development-caused habitat loss and degradation, livestock grazing, and road construction for logging and mining projects. Decreased water quality and quantity, competition from nonnative fish species, hybridization, and whirling disease also present major dangers.

POPULATION TREND: Colorado River cutthroat are extremely imperiled and are now found in only 5 percent of their historic range — typically in isolated headwater streams with limited access to other populations. Less than 1 percent of the trout’s former range is populated by trout with a high level of genetic integrity. Sixty-two percent of robust populations are found in locations strongly correlated with designated roadless areas, emphasizing the importance of preserving intact wilderness.

 

Colorado River cutthroat trout photo courtesy BLM