Slideshow of cutthroat trout
Early season fly fishing in Montana – hatches
- Fishing 101: Take your kids fishing this spring and summer – tips and resources
The cutthroat trout (Oncorhynchus clarkii) is a species of salmonid and is native to western North America. It is the Montana state fish. There are two subspecies of native cutthroat trout in Montana; the westslope cutthroat trout and the Yellowstone cutthroat trout. Both subspecies are a species of special concern. Cutthroat trout are distinguished from other trout by the red slash of color near the lower jaw and this is where they get their name.
Both the westslope cutthroat and Yellowstone cutthroat trout, as stated by Montana, Fish Wildlife and Parks, have tiny teeth on the floor of their mouth behind the base of the tongue and between the gills. These tiny teeth are embedded in the tissue and very hard to see. These basibranchial teeth are present in pure and moderately hybridized cutthroat trout but are absent in rainbow trout.
In general, Montana westslopes are native to the upper Missouri River and Milk River but not the Yellowstone River to the south. Yellowstone cutthroat trout are found south of westslopes on both sides of the Continental Divide.
Their range has been reduced by destruction due to dewatering of streams by irrigation withdrawals, mining, grazing, and logging. Population densities have been reduced by competition with nonnative brook, brown and rainbow trout since these were artificially introduced in the late 1800s and early 1900s. The most serious current threats to the subspecies are interbreeding and hybridization with introduced rainbow trout (resulting in cutbows). In Yellowstone and Heart lakes in Yellowstone National Park, lake trout prey upon cutthroat trout to fifteen inches in length. Whirling disease is also a threat in major spawning tributaries.
Cutthroats require pure, cold water conditions for survival, secure connected habitat (river tributaries and main stems), and protection from introduced non-native fish. When these requirements are not met, the populations plummet. All cutthroat trout require flowing water to spawn successfully. Ponds and lakes must have inlet or outlet streams for cutthroat for self-sustaining populations.
Their food is primarily insects and zooplankton. Cutthroat spawn in the spring in running water and burying their eggs in a nest called a redd. The eggs hatch in a few weeks to a couple of months. The newborn fry frequently migrate back to lakes to mature.
The westslope cutthroat (Oncorhynchus clarki lewisi) is named in honor of Meriwether Lewis and William Clark.
The westslope cutthroat trout tends to have more small spots by the tail, few below the lateral line and none by the pectoral fin and the fish is more of a silvery or greenish color. Coloration varies, but generally they are silver with yellowish hints, though bright yellow, orange, and especially red colors. They are more colorful than Yellowstone cutthroat. The average length of the fish is about 8-12 inches and rarely exceeds 18 inches.
The westslope cutthroat’s historical range was all of Montana west of the Continental Divide as well as the upper Missouri River drainage. Westslope cutthroat are common in both headwaters lake and stream environments. This fish has been seriously reduced in its range by hybridization with rainbow and/or Yellowstone cutthroat, and habitat loss and degradation.
The Yellowstone cutthroat (Oncorhynchus clarkii bouvieri) is native to the Yellowstone River drainage of southwest and south-central Montana. Originally their range was as far downstream as the Tongue River, but today pure, unhybridized populations are limited to some headwaters streams and Yellowstone National Park. Much of their spawning habitat in tributaries of the upper Yellowstone River has been lost to irrigation withdrawals which dewater the streams before spawning and egg-incubation are completed in July and August.
Yellowstone cutthroat trout have medium-large, black spots that tend to be concentrated near the back of the fish. It is a drab brownish, yellowish, or silvery color, with brighter colors generally absent even in mature fish. Spawning males can be a golden brown color.
In general, Yellowstone cutthroat are larger than westslope cutthroat. They can range from 6-26 inches as adults, but are most commonly 6-10 inches. Though their main diet is insects, they are known to eat fish as part of their diet.
For more information visit the following sites:
- Rainbow trout and brown trout
- Montana Fish, Wildlife and Parks – about cutthroat trout
- Trout Identification The Clark Fork Watershed Education Project (CFWEP)
Read articles about some western Montana rivers where you will find cutthroat trout:
- Fishing articles
- Bitterroot River
- Big Hole River
- Blackfoot River
- Montana Fly Fishing Blog – entries about western Montana rivers, fishing, hatches and more
- Higher resolution photos at Merle’s photosite on SmugMug
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