The Bluehead sucker is one of six catostomidae endemic to Arizona. There are a total of 23 members of the Catostomus discobolus, all of which can be found in North America. C. discobolus and C. yarrowi are two sister subspecies that have very similar Arizona habitats.

Description

The Bluehead Sucker is the largest of all Arizona endemic suckers, reaching lengths of over 11.8 inches. Their colors are very similar to the Desert Sucker, with dark green or dark silvery top portions and light yellow bottoms. The Bluehead has the largest lips of any sucker and has tiny papillae on the lower lip. This is also the only species with the absence of an inguinal process, just behind the pectoral fins, distinguishing it from the other eight suckers. The lower lip is slightly notched at the midline, with lateral line scales in large numbers that range from 70 to 100. They have 7 to 9 dorsal fin rays and a smaller amount of caudal fin rays. During breeding, the males obtain a blue patch on the top of their large heads, and the lower fins become yellow/orange with red/rosy lateral lines. These drastic coloration changes are probably due to sexual selection and female mate choice. An easy way to distinguish the Bluehead from the other Arizona suckers is to notice the distinct cartilaginous lower jaw.

Distribution in Arizona

Primary records are concentrated at the Colorado River

Colorado River

The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 main stem and the Grand Canyon

Grand Canyon

The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...

 tributaries, as well as the Colorado River drainages at Lake Mead

Lake Mead

Lake Mead is the largest reservoir in the United States. It is located on the Colorado River about southeast of Las Vegas, Nevada, in the states of Nevada and Arizona. Formed by water impounded by the Hoover Dam, it extends behind the dam, holding approximately of water.-History:The lake was...

. Blueheads are also found at Snake River above Shoshone Falls

Shoshone Falls

Shoshone Falls is a waterfall on the Snake River located approximately five miles east of Twin Falls, Idaho. Sometimes called the "Niagara of the West," Shoshone Falls is 212 feet high—45 feet higher than Niagara Falls—and flows over a rim 1,000 feet wide.A park overlooking the waterfall is...

and Bear/Weber River drainages. There are scattered reports around the Bonneville Basin. Arizona Bluehead sucker distributions are more specifically the Clear, Bright Angel, Shinumo, Kanab, and Havasu Creeks rarely below Diamond Head. Some can be found near the Navajo Reservation and the San Juan drainage. Their biotic communities are restricted to aquatic wetland and riparian zones within Arizona, with a more restricted elevation distribution of 609 to 2060 meters.

Habitat

Bluehead suckers prefer larger streams and rivers due to their larger size, however they can be found in a variety of habitats (Sublette et. Al. 1990). This species has a wide temperature preference as well, ranging from cold mountain brooks at 12 degrees Celsius, to warmer desert rivers at 27 degrees Celsius. If times are good and water is clear, the suckers will stay in shallow steams and eddies during the day, finding their way to hard-bottomed streams to forage at night. Primary spawning areas include a high concentration of juvenile minnows in the Grand Canyon Tributaries and Colorado River drainages. Populations will remain stable unless humans destroy habitats.

Reproduction

The Bluehead sucker has unique spawning techniques, which make it different from most of the other Arizona native fish. Arizona fish usually mate and breed during the winter months, due to specific physiological parameters and water temperature preferences. The Bluehead sucker is the opposite, preferring the spring/summer months and much warmer water temperatures, exceeding 15.72 degrees Celsius. Males will join females in gravel/sandy-bottomed streams and copulation begins, taking only a few seconds. In the Grand Canyon Tributaries, mating can extend even later into the year through April, May, and July. This species will not mate unless the water depth is strictly fewer than 1 meter, probably because the shallow water is easily heated to their desired temperature by the sun. Juveniles grow exponentially fast, reaching lengths of 60 mm and sexual maturity within the first year.

Biology

Suckers use their cartilaginous jaws to scrap the algae and detritus off the stones at the bottom, and despite any shortages of these foods, suckers show little seasonal movement. Diatoms, detritus, algae, and other organic debris have been found in the gut. Bluehead suckers are unique in that they are the only members of the genus to hybridize with other members of the same genus, increasing gene flow among species. They can also live to be more than twenty years old.