The ventral fins of the lumpsucker are modified to form a suction disc used to cling to rocky substrates. The skin is coloured slate grey to blue and is scaleless. Small bony lumps cover the body, with lateral rows of larger bony thorns along the body. The dorsal fin is situated behind a distinct dorsal ridge that is taller in the females. Adults grow between 30-50 cm in length.The colouring in the males changes to blue dorsally and red or orange ventrally during the breeding season. Between February and May, females lay their eggs in shallow coastal waters. Males guard the eggs for 6-7 weeks. The newly hatched fish are 6-7 mm in length and have a 'tadpole like' form. Eggs of the lumpsucker are also commercially harvested as a form of caviar.