Montana's state fish, the Yellowstone cutthroat trout, is identified by red slash marks on either side of the lower jaw and is native only to the Yellowstone River drainage. It feeds on aquatic insects, lays eggs in clean-graveled riffle areas, and rests in cool, clear pools. The fish is highly selective about its habitat and cannot survive in degraded streams and rivers. It is harmed by the introduction of non-native fish such as rainbow and brook trout, and overfishing adds to its difficulties. As a result, the Yellowstone cutthroat trout now lives in only a fraction of its historic range.