|Listed||June 11, 1985|
|Description||Dwarf, olive-gray or olive-green with a white to yellow belly.|
|Habitat||Small streams with shallow pools and good cover.|
|Food||Aquatic invertebrates, algae, detritus.|
|Reproduction||Spawns May and June.|
|Threats||Siltation, hybridization, habitat alteration.|
The Modoc sucker, Catostomus microps, is a dwarf species of the family Catostomidae. Individuals begin to mature at 2.75-3.3 in (7-8.5 cm) with few adults exceeding 4.2 in (18 cm) in length. The Modoc sucker is deep gray to bluish or green-brown to deep gray-olive above. The sides lighten to yellow or white on the belly. It is cream-colored to white ventrally, with caudal, pelvic and pectoral fins that are a light yellowish orange. A bright orange band appears on the sides of the males during spawning season.
The Modoc sucker feeds on bottom-dwelling invertebrates, algae, and detritus. Stomach contents have revealed that half the diet may be detritus supplemented with diatoms, filamentous algae, chironomid larvae, crustaceans, and aquatic insects.
Adult suckers usually remain close to the bottom. Large numbers of papillae and taste buds on the downward turned mouth, limited eyesight, and the position of the eyes in the middle of the head equip the sucker for bottom feeding.
During the spring, spawning runs from mid-April to the end of May, it ascends creeks or tributaries that may be dry during summer months. Depending on temperature and water quality, the spawning fish travel up to a mile upstream. When spawning, which may occur from mid-morning to late afternoon, two or three males surround a single female who releases eggs, which probably adhere to the gravel substrate. Males may or may not stimulate females with breeding tubercles.
Sexual maturity usually occurs at age three although males may mature sooner. Life expectancy is four and the oldest known specimen was five years old.
The Modoc sucker prefers small streams with low or intermittent flow having soft sediments, clear water, and large shallow pools with overhanging trees or cliffs and undercut banks. The vegetation in the valley and meadowland habitat includes sagebrush and western juniper. Forested habitat areas contain ponderosa pine, Jeffrey pine, California black oak, California incense cedar, and white fir. The riparian areas contain cottonwood trees, aspen, willows, and tall grasses, which provide cover for the streams. Portions of Rush Creek run through a residential subdivision, farmland and pastures.
The Modoc sucker has been found in small tributary streams of the Pit River in Modoc and Lassen counties, California. A 1978 California Department of Fish and Game survey reported the species from eight creeks: Washington, Hulbert, Turner, Willow, Ash, Dutch Flat, Johnson, and Rush. At one time, the species inhabited additional streams, but because it is restricted to small, often intermittent streams it was probably never common.
Presently, the species is restricted to portions of Turner and Rush Creeks, two small drainage systems in Modoc County. The federal government manages about half of the land and the rest is privately owned. Recent information indicates that genetically pure Modoc suckers are restricted to Turner Creek and its tributaries, Washington, Hul-bert, and Johnson creeks, and to smaller unnamed feeder streams. About 1,300 individuals are estimated to inhabit this creek system.
The recent decline of the Modoc sucker can largely be attributed to habitat degradation and to hybridization with the more common Sacramento sucker (Catostomus occidentalis ).
Severe erosion, caused by overgrazing by livestock, has increased the amount of silt carried by streams, dramatically degrading water quality. Grazing sheep and cattle trampled streambanks causing increased erosion. The flooding of pastures and channelization resulted in non-native fish hybridizing with C. microps reducing the purity of the populations, and diversion of water used in irrigation reduced the number and size of pools available to the sucker. Introductions of Salmo trutta and brown trout added competitive pressure to the Modoc sucker. Even before the federal listing of this species, the Bureau of Lands Management voluntarily removed many riparian areas from grazing, which has improved water quality in the watershed to some degree.
Waterfalls, steep gradients, and rocky rapids always separated the Modoc sucker from the Sacramento sucker, which ranges downstream in the larger creeks and reservoirs of the Pit River system. When the Sacramento sucker moved upstream to spawn, these natural barriers prevented its encroachment into Modoc sucker habitat. Artificial channeling of these streams removed many natural barriers, and now the two species are interbreeding. Ongoing hybridization could eliminate the Modoc sucker as a separate and distinct species from many streams. Redirection of stream flow has also allowed predator fish access to the Modoc sucker's habitat.
Conservation and Recovery
Critical Habitat was designated in Modoc County to include 26 mi (42 km) of stream bed and a buffer zone along the banks of Turner, Washington, Hul-bert, and Johnson creeks. Through cooperation of Fish and Wildlife Service, the Forest Service, and the California Department of Fish and Game, the Modoc sucker has been reintroduced into Turner Creek, and plans have been developed to rehabilitate Rush Creek and reintroduce the Modoc sucker there.
The Recovery Plan calls for the protection of existing populations and the establishment of at least two additional populations. To achieve these goals, FWS recommends reducing timber rights near the habitat; revegetate and rehabilitate habitat; restrict agricultural practices that cause siltation; restrict road maintenance activities; maintain the water table and flow; remove exotic brown trout from the habitat and prevent its return; restrict cattle that damages vegetation; and prevent stream bank and channel modification. FWS also hopes that new populations can be established by acquiring private land along Johnson and Dutch Flat Creeks; fencing and stabilizing Dutch Flat Creek; and translocating wild individuals to both locations.
U.S. Fish and Wildlife Service
Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave
Portland, Oregon 97232
California Department of Fish and Game. 1980. At the Crossroads: A Report on the Status of California's Endangered and Rare Fish and Wildlife. State of California Resources Agency, Sacramento.
Martin, M. 1972. "Morphology and Variation of the Modoc Sucker, Catostomus microps Rutter, with Notes on Feeding Adaptations." California Fish and Game 58:277-284.
Mills, T. J. 1980. "Life History, Status, and Management of the Modoc Sucker, Catostomus microps (Rutter) in California, with a Recommendation for Endangered Classification." Endangered Species Program Special Publication 80-6. California Department of Fish and Game, Inland Fish.
Moyle, P. B. and A. Marciochi. 1975. "Biology of the Modoc Sucker, Catostomus microps, in Northern California." Copeia 1975:556-560.
U.S. Fish and Wildlife Service. 1983. "Action Plan for the Recovery of the Modoc Sucker." U.S. Fish and Wildlife Service, Sacramento. 14 pp.