Named for the fiery slashes beneath their jaws, westslope cutthroat trout (Oncorhynchus clarkii lewisi) hold a storied place amongst Montana's fish. One of two state fish alongside closely-related Yellowstone cutthroat trout, westslope cutthroat were once found from the Continental Divide westward and throughout the Missouri River's headwaters. But habitat destruction and rampant hybridization with nonnative rainbow and Yellowstone cutthroat trout have fractured their native range.
Listed as a Montana Fish of Special Concern, remaining pure populations of westslope cutthroat endure via conservation stocking programs. These are now, once again, widely distributed throughout the upper Missouri River basin as a result of ambitious restocking programs.
Typically measuring 6-16 inches in their stream and lake habitats, westslope cutthroat rarely exceed 18 inches.
Westslope cutthroat have smaller spots than other cutthroat subspecies, concentrated mostly below the lateral line. Their silver bodies glimmer with golden hues, though some express more vibrant yellow, orange, and red than coastal or Yellowstone relatives. When hybridized with Yellowstone cutthroat, spotting and coloration blend between the two types. Rainbow trout hybrids sport telltale spots on the head and forward lower flank along with reduced scale and increased caecal counts. Continued conservation can preserve the westslope cutthroat trout's unique place in Montana's waters.