Cutthroat trout, an iconic North American fish, are recognized by distinctive red or orange markings under their lower jaw. These markings, resembling a “cut throat,” gave the fish its common name. While consistent, their size varies considerably based on environmental and genetic influences.
Typical Size Ranges
Adult cutthroat trout typically measure 8 to 16 inches and weigh 4.4 to 8.8 pounds. However, their overall size range is broad, from 6 to 40 inches in length and 4 ounces to 6 pounds in weight. Stream-resident populations are smaller, often weighing 0.4 to 3.2 ounces. In contrast, cutthroat trout in larger lake environments can reach 12 to 17 pounds.
Factors Influencing Growth
Several factors influence cutthroat trout growth, with environmental conditions playing a significant role. Food availability and quality, such as insects and smaller fish, directly affect a trout’s growth rate and ultimate size. Water quality is important, as these cold-water fish thrive in clear, oxygen-rich environments with temperatures typically between 40°F and 60°F.
Habitat characteristics, including space, cover, and water flow, also contribute to growth. Streams with limited space or a lack of deep pools may result in smaller fish, while larger, more complex habitats support bigger individuals. Age also plays a part, with cutthroat trout usually reaching maturity between three and seven years, and some living over a decade. While genetics establish growth potential, environmental conditions often limit the size a fish achieves.
Size Variation Among Subspecies
Cutthroat trout are divided into numerous subspecies, each possessing unique genetic traits and native ranges that influence their adult size potential. The Lahontan Cutthroat Trout (Oncorhynchus clarkii henshawi) is recognized as the largest subspecies, historically growing to impressive sizes. In large lake environments, these fish were known to reach lengths of up to 39 inches and weights of 40 to 50 pounds. While stream-dwelling Lahontans are much smaller, lake-dwelling populations average 5 to 10 pounds and measure 8 to 22 inches.
Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) exhibit a different size pattern, particularly their “sea-run” forms that migrate to saltwater. These sea-run individuals typically average 2 to 5 pounds, reaching 18 to 24 inches. While they can grow larger, sometimes up to 28 inches and almost 18 pounds, such sizes are less common. Stream-resident Coastal Cutthroat Trout are generally much smaller, weighing 0.4 to 3.2 ounces.
Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) are generally smaller than their Lahontan counterparts. These trout typically measure 6 to 16 inches, rarely exceeding 18 inches. Their average weight usually falls between 2 to 3.3 pounds. Environmental conditions and genetic potential determine these differing size capabilities across the vast distribution of cutthroat trout.
Record-Setting Catches
The largest cutthroat trout officially recorded was a Lahontan Cutthroat Trout, weighing 41 pounds and measuring 39 inches long. This record-setting fish was caught in 1925 by John Skimmerhorn at Pyramid Lake, Nevada. Pyramid Lake is renowned for producing large Lahontan cutthroat trout due to its abundant food sources, such as tui chub, and favorable habitat conditions that allow for extended growth.
Reaching such sizes is rare and typically occurs in environments offering abundant food availability, ample space, and conditions that support a long lifespan. While the 1925 record stands, large cutthroat trout continue to be caught. For example, a 31-inch Bear Lake cutthroat was recorded in Utah in 2021, and a 21.5-pound Lahontan was caught in Pyramid Lake in 2023. These catches underscore the potential for cutthroat trout to grow to significant dimensions under optimal circumstances.