The Atka mackerel, Pleurogrammus monopterygius, is a mackerel in the family Hexagrammidae. Atka mackerel are common to the northern Pacific ocean, and are one of only two members of the genus Pleurogrammus – the other being the Arabesque greenling (Pleurogrammus azonus). The Atka mackerel was named for Atka Island, the largest island of the Andreanof islands, a branch of the Aleutians.
Able to live up to 14 years, the largest Atka mackerel recorded was 56.5 cm long; the heaviest recorded weight was 2.0 kg. Adults have five vertical, blackish bands on their bodies, which are normally yellowish. Atka mackerel can be distinguished from other, similar species by the number of spines and rays that they have on their fins. They have 21 spines, and anywhere from 25-29 rays on their dorsal fins, and only one spine (but 24-26 rays) on their anal fins.
Found exclusively in the northern Pacific, Atka mackerel are known from Cape Navarin in the Bering sea, and from Stalemate and Bowers Bank in the Aleutian chain to Icy bay, Alaska. They can also be rarely seen as far south as Redondo Beach, California.
Atka mackerel can generally be found from the intertidal zone to depths up to 575 meters.
Atka mackerel migrate from shelves to coastal waters to spawn which occurs (in the Aleutians) from July to September. Their eggs adhere to crevices in the rocks, and incubate for 40-45 days. Males guard the clutches of eggs until they hatch. Atka mackerel feed on copepods and euphausiids. They are, in turn, preyed upon by several species, such as the coho salmon and the endangered Steller sea lion.