In some parts of Idaho, anglers are scrambling to convince conservation groups to protect native cutthroat trout populations. Unfortunately, cutthroat have become more threatened by invasive rainbow trout in recent years. Cutthroat trout play an essential role in ecosystems as both prey and predator, making them a key character in the ecological chain. Current policies and management plans reflect an increased interest in including cutthroat in native biodiversity conservation efforts.
Idaho’s Fish and Game organization uses electrofishing every fall to estimate trout numbers. The state’s plan calls for a reduction of rainbow trout and an increase in cutthroat trout. The 2020 survey revealed that cutthroat populations were at a record high, but rainbows were still too high to fit the state’s management plan.
Rainbow Trout creates a unique problem for Idaho’s management staff. Rainbows are naturally more aggressive than cutthroats and are known to eat the eggs of other fish. The controversy over management comes from local anglers’ love of the fish. Rainbow trout and other invasive species harm the ecosystem but are worthy catches for fishermen.
There are other invasive species that management teams have trouble managing, but local demand supports the preservation of rainbow, brook and brown trout, all of which are non-native salmonids. To appease local desires and the demands of the ecosystem, management has elected to only target non-native species if a decrease in population would benefit cutthroat.
Water levels are important for trout and, due to irrigation and hydropower diversions, water levels have dropped in the Snake River and several other rivers. These diversions can make habitats less hospitable and impact natural water flow. Additionally, runoff from irrigation channels can kill native fish populations as herbicides backflow into running water.
Typically, trout will migrate throughout the year due to fluctuating dissolved oxygen levels. Furthermore, decreased water levels can throw trout migration patterns out of sorts. In response, the U.S. Bureau of Reclamation typically releases water into the Snake River to balance water use.
Like other conservation efforts around the country, the team working on the Snake River engages in stocking as well. In their 2019-2024 Fishery Management Plan, Idaho has emphasized cutthroat as a species worthy of focus. The IDFG has stated that cutthroats must be considered in fisheries, land, and water management.
It is important to note that the IDFG seeks to manage the fish populations currently located in Snake River and other Nevadan waterways. The group does not wish to exterminate rainbow trout or other non-native species. Instead, the organization plans to prevent over-abundance and protect native populations simultaneously.