General Information

Habitat Requirements

Modoc suckers are primarily found in mud and rock bottom pools in small streams and occupy an intermediate zone between the high-gradient and higher elevation, coldwater trout zone and the low-gradient and low elevation, warm-water fish zone (Reid 2008). The elevational range of the Modoc sucker is from about 4,200 to 5,000 feet in the upper Pit River drainage (Ash and Turner Creeks) and from about 4,700 to 5,800 feet in the Goose Lake sub-basin (Reid 2008). Cover consists of overhanging banks, larger rocks, woody debris, and aquatic rooted vegetation or filamentous algae. Larvae occupy shallow, vegetated margins and juveniles tend to remain free-swimming in the shallows of large pools, particularly near vegetated areas, while larger juveniles and adults remain mostly on, or close to, the bottom (Moyle and Marciochi 1975).

Food Habits

Modoc suckers feed on algae, aquatic insects, and small crustaceans found in mud or in algal filaments (Moyle 2002). Chironomid (midge) larvae may be especially important in the diet, but the jaw structure suggests specializations for scraping algae from rocks.

Movement / Home Range

Modoc suckers likely do not move large distances but do move upstream to spawn and move downstream when water levels drop in summer.

Reproductive Strategy

Both sexes mature in their third year at a length of about 5 inches (12 cm; Moyle 2002). Spawning occurs in gravel at the lower end of pools or in riffles in small tributaries, including those that are intermittent, from mid-April to early June when water temperatures are 56 to 61°F (13-16 °C). Several males position themselves on each side of the female and eggs and sperm are released. The fertilized eggs fall into the gaps in the gravel. Females produce up to 12,000 eggs per season (Moyle 2002).

Other

A greater understanding of the genetic relationships and natural gene flow between the Modoc sucker and Sacramento sucker has reduced concerns over hybridization between the two species (Reid 2008; USFWS 2009). The most significant threat to the Modoc sucker is nonnative predatory fish, especially largemouth bass and brown trout.