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Li <br />b <br />collected in August 1983 immediately upstream of the Colorado River bridge at <br />Parachute was only tentatively identified as a razorback sucker (Valdez et al. <br />1985). Past observations (Patrick Martinez, pers. comm.) and recent captures <br />(1990) of razorback sucker in Highline Reservoir, an irrigation storage <br />reservoir that receives water diverted from this reach, strongly suggest that <br />razorback sucker recently occurred upstream of Government Highline Diversion <br />Dam. Government Highline Diversion Dam, completed in 1916, is a formidable <br />barrier (16-foot high) to the upstream movement of fish at all flows. It is <br />likely that the razorback sucker found in Highline Lake and near the town of <br />Parachute were spawned in the reach upstream of Government Highline Diversion. <br />10 Predation by ictalurids hampered successful reintroduction efforts in the <br />lower basin (Marsh and Minckley 1989; Marsh and Brooks 1989). The stream <br />reach from Rifle to Debeque might qualify as a desirable area to attempt to <br />restore razorback sucker because 1) side channel and backwater habitat has <br />been judged relatively abundant, 2) this stream reach is impacted far less by <br />water diversions than the immediate downstream reach (e. g., the 50-mile reach <br />from Government Highline Diversion to Salt Wash), and 3) native suckers and <br />roundtail chub are numerous and non-native predaceous fishes are less abundant <br />than in other reaches. Channel catfish (Ictalurus punctatus) are apparently <br />nonexistent upstream of Government Highline Diversion (unpublished USFWS data <br />1990, 1991). However, black bullhead (I. meJas) are found there because of <br />escapement from gravel-pit ponds adjacent to the river. This determination is <br />based on observations made by CDOW and USFWS personnel during efforts to <br />collect adult razorback sucker in this stream reach during 1990 and 1991 <br />(unpublished USFWS data 1990 and 1991) and earlier fishery surveys (Valdez et <br />al. 1982; unpublished CDOW data 1988; Kevin Bestgen, pers. comm.). <br />23 <br />10