Latin name

Scomber japonicus

Other name

Pacific mackerel, or Pacific chub mackere.

Identification

The chub mackerel has an elongated, spindle-shaped body with a thin, laterally compressed caudal peduncle with 2 lateral carinae and no longitudinal middle carina between them. The body is completely covered with fine cycloid scales. There is a well developed swim bladder. The shell in the anterior part of the body, formed by large scales, is absent. The lateral line is almost straight, with a slight wavy curve. Teeth small, conical. Palatine teeth arranged in one or two merging rows. Gill stamens slender, of medium length, with 37-47 stamens on first gill arch. Scales on lateral line 200-233. Vertebrae in dorsal vertebrae 14, in caudal vertebrae 17. The snout is pointed. The anterior and posterior margins of the eyes are covered by a fatty eyelid. Gill stamens visible through wide open mouth. 

Features of fish fins

Behind the soft dorsal and anal fins is a row of 4-5 additional fins. The first dorsal fin has 9-10 rays, the second dorsal fin has 11-12 rays. The distance between the dorsal fins is less than the length of the base of the first dorsal fin. The pelvic interdorsal spur is low and unbranched. The caudal fin is hard and broadly forked. The anal fin begins just behind a vertical line drawn through the beginning of the second dorsal fin. The anal fin has 11-12 rays. Pectoral fins are short. 

Fish colouring

The back of the chub mackerel is dark blue or greenish-blue, covered with wavy dark transverse lines. The flanks are yellowish, and the belly is silver-white or bluish-grey with wavy interrupted lines.

Distribution

Widespread in temperate, subtropical and tropical waters. Indo-Pacific: Absent from the Indian Ocean except in South Africa, northwest of the Western Cape. There are reports from the Atlantic Ocean, including the Mediterranean species is Scomber coli, and from the Red Sea and northern Indian Ocean is Scomber australasicus. In Russia it is harvested off the Kuril Islands.

Habitat

Subtropical marine oceanodromous species. Inhabits coastal areas with temperatures ranging from 10 to 27° C. These meso- and epipelagic fishes are found above the continental slope from the surface to depths of 300 m.

Size

Maximum length: 64.0 cm for males; total length for the same: 30.0 cm. Maximum reported weight: 2.9 kg.  Maximum life expectancy: 5-8 years.

Behavior

A gregarious fish, it is mainly found in coastal waters. Often forms aggregations in the epipelagic zone, in areas of underwater elevations. Adult fish have developed gregarious behavior, begins to be well manifested in young fish 3 cm long. In summer, chub mackerel migrates to waters subject to seasonal warming, significantly expanding its range. After spawning, fish inhabiting the waters of the Far East Pacific migrate northward to feeding areas in the spring. Migrations occur both inshore and in the open ocean. Travel speeds range from 100-450 miles per month. In July the fish reach the east coast of Hokkaido, in August-September mackerel aggregations are observed near the southern Kuril Islands, and in October the return migration south to spawning areas begins. Mackerel belonging to the North American population migrate north from the central California coast after spawning. Off the coast of the African continent, the migration route follows the coast of West Africa.

Food and feeding habits

Chub mackerel feeds on zooplankton and adapts well to the composition of the food base. Its diet is based on mass aggregations of small animals in the feeding area: euphausiids, copepods, cephalopods, scallops, salpids, polychaetes, crabs, small fish, fish eggs and larvae. A seasonal change in diet is observed. Mackerels, 35-40 in length, feed mainly on fish. Cannibalism is observed in large individuals. They feed mainly at dusk and during the day.

Reproduction

Chub mackerel spawn in groups. Eggs and larvae are pelagic. Spawning is batch spawning. Spawning most often occurs at water temperatures between 15° and 20°C. They spawn in batches of 250-300 eggs per gram of fish, with the total number of eggs per female ranging from 100,000 to 400,000. The larvae hatch from the eggs at a length of 2.7 mm. After one month their length is 3.3-6.9 cm, after 2 weeks 10.2-12.2 cm, and 3 months after hatching 15-18 cm. The length of juveniles reaches 19-20 cm by the end of the first year of life. Mackerel grow fastest in the first year, then growth slows. Fish reach sexual maturity at a length of 24-30 cm at the age of 3-4 years, less often at 2 years, depending on the geographical habitat. 

Fishing

Valuable commercial fish. The main fishery is in the northwestern part of the Pacific Ocean. Russia and Japan catch it mainly in coastal overwintering aggregations. The largest catches are observed in September-November. The fishery is conducted with deep trawls, purse seines, hauls, gillnets, driftnets and seine nets. 

Relationship with a person

Chub mackerel is marketed in frozen, smoked, canned and salted forms. It is used in Chinese medicine.