Cutbow

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Cutbow is a fertile hybrid fish created when rainbow trout and cutthroat trout breed. There are four named cutbow hybrids, but only coastal cutbow and westslope cutbow occur where the two parent species naturally overlap. Lahontan and Rocky Mountain cutbow come from rainbow trout being introduced into waters that already had cutthroat trout.

Hybridization can threaten native cutthroat trout by mixing their genes, a problem fishery managers work to prevent. Because of this, some programs remove cutbows from wild populations, while in other areas cutbows are stocked to support fishing.

Cutbows can occur naturally where the parent species’ ranges meet, but human stocking has increased their presence in North America. They’re often hard to tell apart from rainbow or cutthroat trout just by looks because of variation. A few clues can help: cutbows usually have a faint reddish or orange slash under the jaw like cutthroat trout; in some populations, such as Yellowstone cutthroat trout, a white edge on the anal or dorsal fin can hint at rainbow ancestry. When coastal cutthroat and rainbow trout cross, traits like hyoid teeth and the strength of the jaw slash can be useful.

In hatcheries, cutbows are made when female cutthroat eggs are fertilized by male rainbow trout. Spawning overlap in the wild can increase hybridization. Wild cutbows are often viewed as a threat to wild cutthroat trout and may be removed, though in some places they are stocked to support fisheries.