Smooth lumpfish  The smooth lumpfish ("Aptocyclus ventricosus") is a species of lumpfish native to the North Pacific where it is found at depths down to . This species grows to a length of TL. This species is the only known member of its genus. Smooth lumpfish, or smooth lumpsucker, is a deep sea fish species with a body length of 6–44 cm and body weight of 0.05-4.20 kg on average. They look brownish gray with dark spots dorsally, muddy gray ventrally. They have naked Skin without scales and tubercles. A smooth lumpfish has no dorsal spines or anal spines, eight to nine dorsal soft rays, seven to nine anal soft rays. They have rounded caudal fin, large and broadly based pectoral fins. Their pelvic fins are modified to form a clinging disc with a thickened margin on the ventral surface of the body. They have their first dorsal fins completed embedded under the skin. Smooth lumpfish are widely distributed throughout the North Pacific, especially the Aleutian Basin. They inhabit both near bottom and mid-water layers ranging from 5 to 1700 m. They are preyed by some fish species, marine mammals and sea birds. The preferred diets of smooth lumpfish are medusa and ctenophores. They also feed on pelagic polychaetes and crustacean occasionally. The smooth lumpfish is an iteroparous gonochoristic species with determinate fecundity, group-synchronous ovary organization, total spawning (release of 1 batch of eggs per breeding season), and external fertilization. Smooth lumpfish perform spawning migration from deep-ocean to coastal zones, where breeding occurs over a rocky bottom at depths shallower than 10 m. A thick envelope protects these demersal eggs from mechanical damage during development in the coastal zone. The incubation time between fertilization and hatching is more than 40 days. Males protect the egg clusters after females spawn.