Trout may be a factor contributing to hellbender decline. The Current, Eleven Point, and the North Fork of the White River are home to the Ozark Hellbender, which scientists are scrambling to save from extinction. These rivers are is stocked with trout annually. Some of these flows have segments designated as Blue Ribbon trout streams.
Studies have raised questions about the compatibility of the two species. Hellbenders and trout favor the same rivers and streams for the same reasons: both need the colder, heavily oxygenated water found in these spring-fed rivers. In question is what is considered to be a distinct sub-species, called the Ozark hellbender.
In recent decades, the number of stocked fish has risen in many Ozark rivers and streams as the popularity of trout fishing has grown. Brown trout were stocked in Missouri rivers in the 1920s and 1930s. That resumed again in the 1960s, concentrating on the Current and North Fork.
The Missouri Department of Conservation also has a trout hatchery at the headwaters of the Current River, and another at Bennett Spring, which quickly empties into the Niangua River — both of which are home to hellbenders. Several of the Ozarks’ south-flowing streams are home to the Ozark hellbender, while some of its north-flowing streams are home to the eastern hellbender.
In 2009 studies were launched to determine what was causing the collapse of the Ozark hellbender population, found that the large salamander — at least at the larval stage — may not have the ability to detect the chemical cues that help them recognize trout as a predator. The Ozark hellbender adapted to deal with native bass, sculpins and walleye that prey on them. They evolved anti-predatory behavior that allows them to smell these predatory fish. But when exposed to trout, they do not react defensively. A weak responses of larval hellbenders to chemical cues from introduced predatory trout may be related to the hellbender decline.
MDC has not stocked trout in stream reaches that had not been stocked prior to 2005, and it isn’t stocking the more aggressive brown trout in streams that had been previously stocked only with rainbows. However, there are streams where trout aren’t stocked where hellbender decline has happened. Hellbenders are under assault by sedimentation, subpar water quality, and hereto unidentified diseases.