Trout Talk

Wild or hatchery? Idaho fisheries managers want to know

A rainbow trout from the Snake River. Roger Phillips photo.

The Idaho Department of Fish and Game wants to know if the rainbow trout that swim in the Snake River between two eastern Idaho impoundments are wild or if they’re hatchery fish that have migrated upstream.

The rainbows between Gem Lake, just below Idaho Falls on the mainstem of the Snake and American Falls Reservoir, a giant irrigation and hydropower reservoir, are something of a mystery to the state’s fisheries managers. It’s not known whether the fish are wild rainbows, descendants of hatchery ancestors from past plantings, or if they’re simply hatchery fish that have moved down from Gem Lake or up from American Falls.

And Fish and Game biologists are asking anglers to engage in some minor surgery to help determine the answers to their questions.

Here’s how anglers can help:

  • There are four fin kiosks located throughout the upper portion of the Snake River between American Falls Reservoir and Gem Lake. These kiosks are located at McTucker ramp, Porterville ramp, Cherry Plant ramp and Shelley ramp. Each kiosk has envelopes and instructions on how to process a fin sample. Anglers interested in participating in the study can grab a couple of envelopes before going fishing, even if they plan to release the fish they catch.
  • Rainbows can be identified by heavy spots on the head and white fin tips. Anglers who catch a rainbow trout can clip a small portion (about the size of a hole punch) from one of its fins. A small fin clip as described will likely not affect the trout you release.
  • Anglers should then place the fin clip in an envelope (found at the drop box at each kiosk). One fin clip from each rainbow should be placed in a separate envelope. Fish and Game asks anglers to keep the envelope(s) dry until they are ready to drop it in the drop box.
  • When the fishing is done, anglers can deposit the envelope(s) in the drop box found at the kiosk.

These fin clips provide chromosomal information which can be used to determine a fish’s origin (hatchery or wild). This information helps Fish and Game understand if current fish management strategies are appropriate on this stretch of the Snake River.

Ryan Hilliard photo.