The broadfin thornyhead (Sebastolobus macrochir) has large pectoral fins, which inspired its Greek name macrochir, meaning "long hand". Broadfins are identified with having a red body and gill cavity, black patches on their dorsal fins, and an anal fin that may have black marks. In addition to having deeper bodies (height: back-to-belly), their pectoral fins are not notched as deeply as those of the shortspine thornyhead. Other distinguishing features are their scale-covered branchiostegals and lower pectoral rays that are more highly branched than the shortspine's. The broadfin thornyhead can grow up to 15.2 in. (38 cm).

The broadfin's range extends from the Adak Island region of the Aleutian Islands southwest to the Sea of Okhotsk and south to Japan. They are usually found at depths of 1,320 ft. to 1,980 ft. (400-600 m), and have been found as deep as 4,686 ft. (1,420 m). Broadfins prefer living in cold water temperatures of 35.6° F to 39.2° F (2-4° C), in addition to low-oxygen water. This species is solitary in nature and do not migrate long distances. Among the broadfin's prey are crabs, shrimps, krill, octopi, squids, and brittle stars.

As with the other thornyheads, the broadfins are oviparous; producing egg masses, rather than giving birth to small fishes (viviparity). Spawning can occur twice per year, during periods ranging from January to October depending on location; earlier in southern areas than in northern parts.

The commercial fishery for broadfins is particularly important between northern Japan and the Sea of Okhotsk. The juvenile catch was common for the Japanese during the 1970s, but has greatly diminished since then. Bottom trawl, gillnet, and longline are the current fishing methods used.

Adapted from Love, M. 2002 Sebastolobus macrochir, p. 119. In M. S. Love, M. Yoklavich, and L. Thorsteinson, The rockfishes of the northeast Pacific. Univ. California Press.

AFSC Rockfish Guide (refered to as broadbanded thornyhead)