Reintroduction of the flannelmouth sucker in the lower Colorado River

A single stocking of 611 wild flannelmouth suckers Catostomus latipinnis in 1976 represented the first successful reintroduction of a native fish in the lower Colorado River. Flannelmouth suckers ranging in age from young of the year to 24 years were captured during 1999–2001; their population was estimated as at least 2,286 (95% confidence interval, 1,847–2,998). Recruitment appeared sporadic, consisting of consecutive years of low recruitment (<10%) supplemented by a stronger (31%) year-class. Historically, this native fish was rare and was believed extirpated from the lower river by 1975, but it now reproduces naturally in a reach dramatically altered by water development. This successful reintroduction indicates that one native fish can successfully tolerate environmental alterations whereas another, the razorback sucker Xyrauchen texanus, apparently cannot. Other opportunities may exist in altered rivers to benefit native fishes where they were absent or historically rare.