Modoc suckers are small, usually less than 6 inches (16 cm) standard length, with short heads and small eyes (Moyle 2002). Maximum size is 11 inches (28 cm). Lateral line scales number 73-91. Scales above the lateral line number usually number 15 (range = 14-19); those below the lateral line number 9-12. Dorsal fin rays number 9-12; anal fin rays 7; pelvic fins 8-10 (Kettratad 2001, Moyle 2002). The lower lip is deeply notched, with only one of the 5-6 rows of papillae connecting the two haves (Moyle 2002). The non-breeding color of both sexes is greenish-brown through bluish to deep-grey and olive, and the sides are lighter with generalized mottling and usually with 3-4 darker blotches, and is similar to Sacramento suckers of similar size. The belly is white to cream or yellowish and unmarked. Breeding males have a reddish-orange lateral band, and orange fins; tubercles develop on fins and body.