Idaho State Fish is the Cutthroat Trout

http://www.sos.idaho.gov/elect/emblem.htm

The Cutthroat Trout was designated the state fish by the 1990 legislature. The Cutthroat, along with the Rainbow and Bull Trout, is native to Idaho. The body color varies with the back ranging from steel gray to olive green. The sides may be yellow brown with red or pink along the belly. The Cutthroat name comes from the distinctive red to orange slash on the underside of its lower jaw. The scientific name for Cutthroat Trout, Oncorhynchus clarki, is in reference to William Clark who first described in detail the Cutthroats of the Columbia River. His partner Meriwether Lewis earlier encountered Cutthroats near the great falls of Montana's Missouri River in July of 1805. Cutthroat species found in Idaho are the Westslope Cutthroat which is found in northern and central Idaho and the Yellowstone Cutthroat which is found in southeastern Idaho.