Historically, the Malheur River Basin supported anadromous steelhead trout Oncorhynchus mykiss that spawned in the upper basin. However the construction of Warm Springs Dam in 1919 on the Middle Fork Malheur River and Agency Dam (Beulah) in 1935 on the North Fork Malheur River blocked anadromous fish passage into the upper portions of the basin. Brownlee Dam on the Snake River ended movement of anadromous fish into the Malheur River in 1958.

Existing populations of redband trout O. mykiss are either resident or have adopted a resident life history after dam construction. However, few data exist that describe current distribution and abundance of redband trout in the Malheur River. Some limited surveys have occurred in various portions of the basin and yet in other portions it is unknown if redband trout exist. A systematic, basin-wide survey of redband trout does not exist.

In 2007, the Native Fish Investigations Project, in conjunction with the Burns Paiute Tribe, conducted a survey for redband trout throughout the Malheur River Basin. This was the first comprehensive look at redband trout status and distribution basin-wide. We employed the same sampling protocol used by EPA’s EMAP to select a spatially balanced representative sample sites throughout the basin. Two field crews conducted two-pass removal density estimates at 90 sites between 25 June and 20 September 2007. For comprehensive methods and results please refer to the final report below.