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" Among the remaining six native fish spelfies, all persist in the basin. Cutthroat trout (Colorado . River subspecies) survives in several isolated headwater tributaries. Roundtail chub is extremely rare in the San Juan and Animas rivers, but may be more common in other streams (Piedra, Los Pinos, La Plata and Mancos rivers). Mottled sculpin occurs mainly in the Animas River, but is not common. Speckled dace is generally distributed in the drainage, particularly in upper tributaries, the Animas River, and the San Juan River upstream of Bluff. Flannelmouth and bluehead suckers inhabit most reaches of the San Juan and Animas rivers as well as lower reaches of some tributaries. Non-native Fish Fauna Since the late 1800's, at least 40 non-native fish species have been introduced to the Upper Colorado River Basin. In the San Juan River basin, 23 non-native fish species have been reported (Table 2). Of these, 21 have been documented in the San Juan River since 1987. In warm water reaches of the main stem San Juan River, common carp and channel catfish were the only common and generally distributed non-native fish species. Rainbow, cutthroat (Snake River subspecies), and brown trout were common in coldwater reaches of the San Juan River (including the Navajo Dam tailwater reach) and its upper tributaries. Red shiner, fathead minnow, and mosquito fish were the most common non-native species found in low-velocity habitats associated with the mainstem San Juan River. Other non-native fish species, such as black bullhead, plains killifish, green sunfish, and largemouth bass, were very rare and probably derived from upstream or downstream or from off-channel impoundments. Some non-native fish species were introduced by federal, state, and tribal agencies to establish food or recreational fisheries while others became established as a result of bait minnow, fishermen, or accidental releases. In New Mexico and Utah, stocking of non-native warm water species has been discontinued, but non-native salmonids are still stocked in suitable habitats in Colorado and New Mexico (including the Navajo Dam tailwater reach). . . 4