Trout are native to Utah waters. These trout are actually the only trout
that are native to Utah. They are called Bonneville Cutthroat trout
because they lived in Lake Bonneville, an ice age lake that covered a
large portion of Utah. Over time, temperatures began to rise and Lake
Bonneville began to dry up leaving the Great Salt Lake. The trout
persisted in the fresh waters streams draining into Great Salt Lake.
Before human settlement in the late 1800's, these trout were found in Utah
and most streams of the Wasatch mountains.
When Rainbow trout were introduced into Utah waters the Bonneville Cutthroat Trout and the Rainbow Trout hybridized. These hybrids have no basibranchial teeth (Emigration Creek Project). The hybrid Trout compete with the native trout for food and space, and eventually take over the area. The introduction of fish has threatened the pure genetic strains of isolated populations of Bonneville Cutthroat trout. As a result of the competition for food and space by hybrids and other trout species, the Bonneville Cutthroat Trout has lost most of its original territory.