Upper Deschutes Trout Genetics & Hatchery Stocking

Last month a team of scientists from the US Fish & Wildlife Service and the Oregon Department of Fish & Wildlife released a report on redband trout genetics in the Deschutes River below Wickiup Reservoir down to Steelhead Falls.  As you would expect, they found pockets of fairly distinct genetics in various reaches bordered by falls and dams, near the few still viable spawning beds, and in tributaries like the Little Deschutes. They also found evidence of breeding between wild populations and hatchery fish.  I called Erik Moberly, Assistant Deschutes District Fish Biologist, for some more background information and had an interesting conversation.

Over 100 years ago anglers became concerned with declining fish populations in the upper Deschutes, initially caused by over fishing then by environmental damage from irrigation withdrawals.  These conditions dramatically reduced redband trout populations and completely eliminated bull trout.  Initially in response to over fishing, trout stocking began in 1913 and continues to the present.

Over many decades a variety of hatchery fish have been released in the upper Deschutes and tributaries like the Fall River.  Some of these fish originated from out of state, others came from the middle Deschutes.  All of them were inbreed over long periods of time to increase survival in hatcheries creating inferior fish.  Some were even manipulated enough to change their spawning period from spring to fall in an attempt to reduce breeding with wild, native fish.  The end result was weak fish designed for put and take fishing, not survival after release.

In recent years fishery managers have become more aware of the genetic inferiority of hatchery trout and have focused on limiting their impact on wild, native fish.  Stocking in the Deschutes itself has not occurred in many years.  Hatchery fish are now only planted in Crane Prairie Reservoir and the Fall River.  These fish are based on redbands taken from Crane Prairie (“cranebows”).  As managers observed, and the paper confirmed, however, an unacceptable amount of breeding occurred between wild fish and hatchery cranebows, continuing the degradation of wild fish.

In response, all hatchery fish now released in the Fall River and Crane Prairie are sterile (“triploids”), therefore unable to reproduce.  Creating triploids is an expensive process but should eliminate further degradation of existing wild fish.  Of course, genetic damage to the wild fish population has already been done, but nature should take care of this over time.  The added benefit to anglers is that triploid cranebows are robust fish and a pleasure to catch.