Actions > Redistribution

Many study area streams have mixed trout populations.
Moving wild trout from native cutthroat habitat increases the opportunity for natives to survive, even prosper.
Declining stream flows due to climate change increasingly stress cutthroat populations.
That's in addition to habitat competition from brook and brown trout, and population hybridization from rainbows.
Barriers for separating populations are logical where the purpose is to protect natives.

A. Approach

Install exclusion barriers to minimize additional entry of wild species into cutthroat habitat. (See references 1-4 below.)
Apply electro-winnowing to remove and relocate wild trout that are above the barrier.
Use existing structures, such as culverts (exhibits 1 & 2) and bridges, for cost-effective and resilient barrier placements.

Wood planks, 2-in x 6-in, were used at the culvert installation seen above in exhibits 1 and 2.
A single barrier in a concrete culvert is shown schematically in exhibit 3.
Exhibit 4 shows double walls holding rock between, which uses barrier length, not just height, for blocking intrusions.
A concrete pad installed just downstream has been described as functioning as a barrier to trout entering the culvert.

That is, the pad could prevent scouring and creation of a plunge pool from which trout could launch into the culvert [5].
Exhibit 5 shows concrete and steel culvert locations and a bridge at streams in the study area.

Preferred sites have structures that are more resilient to erosion than the streambed and its directly adjacent riparian areas.
For example, concrete or steel culverts can serve well, as can posts and planks that support bridges.
They enable solid anchoring of barriers, which minimizes the opportunity for them to be damaged from high water velocity, such as during snowmelt.

Electro-fishing can be conducted to capture and identify trout species above a barrier.
And also to remove, or winnow, non-native species from the stream.
The technique is demonstrated in the brief video below.
Small tail samples of netted natives also can be collected for DNA analysis to determine genetic heritage.
Fish caught by this approach recover virtually immediately.
The non-native species netted can be relocated.

References (Click or tap to view the document)