Thornyheads (Sebastolobus species) are groundfish belonging to the family Scorpanenidae, which contains the rockfishes. The family Scorpanenidae is characterized morphologically within the order by venomous dorsal, anal, and pelvic spines, numerous spines in general, and internal fertilization of eggs. While thornyheads are considered rockfish, they are distinguished from the “true” rockfish in the genus Sebastes primarily by reproductive biology; all Sebastes rockfish are live-bearing (ovoviviparous) fish, while thornyheads are oviparous, releasing fertilized eggs in floating gelatinous masses. Thornyheads are also differentiated from Sebastes in that they lack a swim bladder. There are three species in the genus Sebastolobus, including the shortspine thornyhead Sebastolobus alascanus, the longspine thornyhead Sebastolobus altivelis, and the broadfin thornyhead Sebastolobus macrochir (Eschmeyer et al. 1983, Love et al. 2002).