A “New” Redband Trout

November 27, 2023 By: Spencer Durrant

Photo: USFWS Fish and Aquatic Conservation/Flickr

Matthew L. Miller penned a wonderful story about the recent discovery of a “new” subspecies of redband rainbow trout in Idaho over in Fly Fisherman MagazineWhile I highly encourage you to read Miller’s account, the highlights are as follows.

Most folks who fish in Idaho’s Big Wood River assume that the rainbow trout they’re catching are descendants of hatchery fish. The Big Wood River flows through south-central Idaho, coming off the south slope of the Sawtooth Mountains through Ketchum, ending its 137-mile run at a confluence with the Malad River. The Malad, in turn, is a tributary to the Snake River.

According to Miller, most biologists and anglers assumed the wild rainbow trout in the Big Wood River were the relatives of hatchery fish from early in the 20th century. However, new research suggests that the rainbow trout in the Big Wood are, in fact, a native subspecies of redband rainbow trout.

As Miller writes, “Steelhead are rainbow trout that migrate to the ocean and back, whereas the term ‘redband’ typically applies to rainbow trout that remain residents in streams. In Idaho, all rainbow trout (Oncorhynchus mykiss) share similar genetics, what is commonly called the ‘interior redband’ lineage. Most hatchery fish trace their origins to California and the Pacific Northwest, which is another lineage, called the ‘coastal rainbow.'”

So, not only are the redbands in the Big Wood native to the drainage, but they’re further enhanced our understanding of trout genetics in one of the last bastions of wild trout habitat in the world.

You can read the rest of Miller’s story here.