Historical Status and Current Trends

Early records indicate that shortnose suckers were once widespread and abundant in the upper Klamath Basin of Oregon and California. This area historically contained over 350,000 acres of wetlands and floodplains. These wetlands protected sucker habitats by reducing erosion forces, removing organic and inorganic nutrients, and maintaining water quality. Agricultural development and associated water and land use changes in the basin have contributed to the significant loss of these wetlands. The resulting reduction and degradation of shortnose sucker lake and stream habitats have led to a significant decline in population size. Although over-harvesting and pollution may have played a role in the species decline, it is believed that the construction of dams, the draining or dredging of lakes, and other alterations of natural stream flow have reduced the reproductive success of shortnose suckers by as much as 95 percent through the loss of suitable spawning habitat. At the time the shortnose sucker was listed as endangered, it was noted that there had been no significant addition of young into the population in 18 years. Currently, the shortnose sucker occupies only a fraction of its former range and is restricted to a few areas in the Upper Klamath Basin, such as the Upper Klamath Lake, Tule Lake, and Clear Lake drainages. Poor water quality, reduced suitable habitat for all size and age classes, and the impacts of non-native fishes continue to threaten remaining shortnose sucker populations.

Description and Life History

Shortnose suckers are distinguished by their large heads with oblique, terminal mouths with thin but fleshy lips. The lower lips are deeply notched. They are dark on their back and sides and silvery or white on the belly. (Moyle 2002). The shortnose sucker can live up to 33 years and is usually less than 50 centimeters (20 inches) in length. The diet of this bottom-feeding species consists of detritus (decomposing organic matter), zooplankton (tiny floating aquatic animals), algae, and aquatic insects. Shortnose suckers reach sexual maturity around six or seven years and then participate in spawning migration. Adult suckers migrate from the quiet waters of lakes into fast moving streams from March through May in order to spawn; they may also spawn in springs from February to late April when water temperatures are a constant 15 C (60 F). Thousands of eggs (from 18,000 for smaller fish to 46,000 for larger fish) are typically laid near the stream bottom in areas where gravel or cobble is available. Once the larvae hatch, they begin migrating back to calmer waters.

Habitat

The shortnose sucker dwells in the deeper water of lakes and spawns in springs or tributary streams upstream from its home lake. Some stream dwelling populations also exist. Areas with gravel or close-set stone (cobble) bottoms are generally preferred for spawning habitat. In addition, spawning streams have a fairly shallow shoreline with an abundance of aquatic vegetation; these areas provide a safe haven for the young larvae during their journey back downstream to their home lakes or the deep, quiet waters of rivers. Shoreline vegetation in both lake and river habitats is important for the rearing of larval and juvenile suckers.

Reasons for Decline

Although a number of factors have contributed to the decline of the shortnose sucker, habitat degradation is considered its primary cause. Streams, rivers, and lakes have been modified by channelization and dams. Grazing in the riparian zone has eliminated streambank vegetation, and has added nutrients and sediment to river systems. Eggs and larvae, for example, suffocate when the water is cloudy, or dry out or get eaten by other fish when they are not protected by aquatic vegetation. Loss of streambank vegetation due to overgrazing, logging activities, agricultural practices, and road construction has also led to increases in stream temperatures, high levels of nutrients (which encourages the buildup of excess algae and bacteria), and serious erosion and sedimentation problems in streams. Such water quality problems have reduced the availability of suitable shortnose sucker habitat and have resulted in major fish mortality. Entire age classes of young suckers are routinely lost due to poor water quality conditions. As a result, few young suckers survive to sexual maturity, and therefore, do not increase the population size. Other factors affecting the decline of the shortnose sucker include previous over-harvesting, chemical pollution from pesticides, herbicides, and forestry practices, and predation and competition from native and non-native fishes such as largemouth bass, blue chub, yellow perch, fathead minnows, and rainbow trout.

Conservation Measures

Conservation efforts for the shortnose sucker focus on the re-establishment of a more naturally functioning ecosystem in the Klamath Basin. Fencing portions of streams to reduce cattle-caused erosion, replanting streambanks with native vegetation, improving forestry and agricultural practices, and assuring adequate water levels in reservoirs will contribute to the recovery of this species. Through coordination of the actions of land use agencies and private landowners, further degradation of sucker habitat can be avoided and steps can be taken to improve current conditions. By minimizing the impacts of future modifications to spawning habitat and restoring waters to a more natural state, recovery of shortnose sucker populations is possible in the Klamath Basin.

References and Links

U.S. Fish and Wildlife Service. 1988. Determination of Endangered Status for the Shortnose Sucker and Lost River Sucker. FR 53:27130-27134.

U.S. Fish and Wildlife Service. 1993. Lost River (Deltistes luxatus) and Shortnose (Chasmistes brevirostris) Sucker Recovery Plan. Portland, Oregon 108pp.