Montana Field Guide

Columbia River Redband Trout - Oncorhynchus mykiss gairdneri

Interior redband trout are a native trout of western North America. There is considerable variation in the life history in this group of trout. Resident stream populations are found throughout the Columbia River basin. A lake variation known as kamloops are found in some larger lakes in the Columbia and Frasier River (British Columbia) basins. A third variation is the steelhead that migrated from the ocean as far as the upper Snake River, Idaho (almost 1000 miles) (Behnke 1992).

Characteristics vary considerably among populations of Montana's stream-resident redband trout, but generally they can be differentiated from the non-native coastal rainbow trout by larger more rounded spots, parr marks that tend to remain into adulthood and are more orange-red around the lateral line surrounded by greenish-yellow, rather than pink-red around the lateral line surrounded by dark green and silver like coastal rainbow trout. Redband trout also have very distinct white tips on the anal, dorsal and pectoral fins.

Montana Range

Redbands are typically a stream-resident fish that make short spawning migrations either in the same stream or often into smaller tributaries.

Redband trout prefer cool, clean, relatively low gradient streams but, in some circumstances, are able to withstand wider temperature variations than their cousins the westslope cutthroat trout.

Interior redband trout feed mainly on aquatic insects but eat what is available to them. Large adults also eat fish. River populations are mostly insect eaters, while zooplankton and forage fish are important in Lake Koocanusa.

Populations of native redband trout, westslope cutthroat trout and introduced coastal rainbow trout coexist in the Kootenai River drainage. Interestingly, redbands have hybridized with westslope cutthroat trout in some drainages and these crosses are considered to be naturally occurring and historic. Hybridization between redbands and rainbows, on the other hand, is considered to be a danger to the continued existence of redband trout.

Interior redband trout reach sexual maturity in 2 to 3 years. They spawn from late April through mid-June, depending on water temperatures. The fry typically emerge from the gravel in mid-July.