Common Name: Razorback Sucker
Scientific Name: Xyrauchen texanus
Appearance: Color olive to brownish-black above, lighter below (often yellow). Sides with brown or pinkish to reddish-brown stripes. Dorsal fin dark; anal fin yellow; caudal fin light yellow-brown. Breeding males black or dark brown on dorsum and upper sides, orange laterally, and bright yellow on belly. Breeding males also have coarse sharp tubercles on the anal, caudal and/or pelvic fins.
Can attain lengths of 1.0 m (3.3 ft.) and weights of 6.0 kg (13.2 lbs) (Minckley 1973). Mouth is subterminal with few papillae on lips; lower lip is separated into two lobes by a medial groove. Adults razorbacks are easily distinguished from other suckers by the prominent predorsal keel. Young lack a keel and may be difficult to distinguish from other Catostomus species. The “keel” along the back and inset eyes are likely adaptive features to the high flood events of historical habitat.
Diet: Razorback suckers feed on algae, insect larvae, plankton, and detritus.
Habitat and Range: Endemic to large rivers of the Colorado River Basin from Wyoming to Mexico. Present distribution of natural populations is limited to Lake Mohave and Lake Mead in the lower Colorado River basin, and in the Green, Colorado, and San Juan rivers in the upper Colorado River basin. Populations are being reestablished in multiple locations (e.g., lower Colorado River, Lake Havasu).
They use a variety of habitat types from mainstem channels to slow backwaters of medium and large streams and rivers, sometimes around cover. In impoundments they prefer depths of a meter or more over sand, mud or gravel substrates. Adult razorbacks tolerate a wide range of temperatures from near freezing temperatures to 32.0o C (89.6º F), with optimum temperatures around 22-25o C (71.6-77.0º F).
Breeding: Razorback Suckers are long-lived. Older individuals in Lake Mohave have been estimated at 40 + years. They tend to grow quickly in the first five to seven years, with growth slow or nonexistent in old individuals. Both sexes are sexually mature by age four. Usually sedentary, but they can travel significant distances on occasion. Spawning occurs from late winter through spring along gravelly shorelines or bays. Evidence suggests that suckers migrated from larger rivers to smaller tributaries prior to spawning. A single female is attended by 2 to 12 males, and the group moves in tight circles over the bottom. Spawning takes place when the group settles to the bottom and with a vibrating action release gametes. The eggs are adhesive and attach to the interstitial spaces within the gravel substrate. The young hatch in a few days and live along the shoreline for a time. Females will spawn repeatedly with several males. Hatching success is highly dependent on water temperature with complete mortality in temperatures less than 10°C (50°F).
Status: Federally listed as Endangered with critical habitat in 1991.
Threats: Altered flow hydrology and cold tailwater releases from reservoirs; water diversions; and predation by and competition with nonnative fishes.
Actions: Conservation actions include: reestablishing self-sustaining populations; managing water to provide adequate stream flows; fish passage construction; restoring floodplain habitat; monitoring fish populations; managing nonnative fishes; broodstock and refugia population development; and investigate and resolve causes of recruitment failure.
Literature Cited and Additional Resources:
U.S. Fish and Wildlife Service. 2012. Five year status review. https://ecos.fws.gov/docs/five_year_review/doc4035.pdf
U.S. Fish and Wildlife Service. Species Profile for Razorback Sucker. https://ecos.fws.gov/docs/five_year_review/doc4035.pdf
Upper Colorado River Endangered Fish Recovery Program: http://www.coloradoriverrecovery.org/general-information/the-fish/razorback-sucker.html