Pacific Chub Mackerel, Scomber japonicus
Pacific Chub Mackerel, Juvenile, Scomber japonicus. Fish caught with a cast net by commercial bait salesmen of the greater Los Cabos area, Baja California Sur, February 2020. Length: 11.0 cm (4.3 inches). Fish caught in a shallow water environment just off the beach which is atypical. Also it is apparent that the juveniles are very similar in stature but significantly less colored when compared with the adults.
Pacific Chub Mackerel, Scomber japonicus. Fish caught from coastal waters off Santa Cruz, California, May 2016. Length: 19.2 cm (7.6 inches). Catch, photograph and identification courtesy of Andrew Hansen, Santa Cruz, California.
Pacific Chub Mackerel, Scomber japonicus. Fish caught from coastal waters off Point Palmilla, Baja California Sur, February 2016. Length: 20.0 cm (7.9 inches).
The Pacific Chub Mackerel, Scomber japonicus, is one of the most common members of the Mackerel or Scombridae Family, that is also known as the Chub Mackerel, the Green Mackerel and the Pacific Mackerel and in Mexico as macarela estornino. Globally, there are four species in the genus Scomber, of which three are found in Mexican waters, one in the Atlantic and two in the Pacific Ocean.
The Pacific Chub Mackerel has an elongated rounded fusiform tuna-like body that is designed aerodynamically for speed. They are silvery with greenish tinges and have blackish oblique stripes that zigzag and undulate on their upper back. They have large black eyes with palatine teeth in single and double rows. Their anal fin is small and originates opposite the second dorsal fin and has 1 spine and 12 to 14 rays followed by 5 finlets; their caudal fin is deeply forked with 2 small keels separated by 1 large keel at the slender base; the first dorsal fin has 9 or 10 spines; the second dorsal fin is widely separated from the first with the distance between being equal to or less than the length of the first dorsal base and is small with 12 rays followed by 5 finlets; and, their pectoral fins are short. Their lateral line runs the entire length of the body.
The Pacific Chub Mackerel is a coastal pelagic species found from the surface to depths of up to 300 m (985 feet). They reach a maximum of 64 cm (2 feet 1 inch) in length and 2.9 kg (7.4 lbs) in weight. As of January 1, 2023, the International Game Fish Association world record stood at 2.17 kg (4 lbs 12 oz) with the fish caught in coastal waters off Guadalupe Island, Baja California in June 1986. They are normally found within 37 km (20 miles) from shore in waters with temperatures between 10oC (50oF) and 22oC (72oF). Young reside around sandy beaches and kelp beds while adults are found in deeper waters. They form large compact structured schools of thousands of individuals and may also form schools with Pacific Bonito, Sarda chiliensis, Jack Mackerel, Trachurus symmetricus, and Pacific Sardine, Sardinops sagax, to compete for food. They undergo extensive summer migrations to cooler waters. Adults are vertical migrators found on the bottom during daylight hours and moving up during the nighttime to opportunistically and non-selectively feed on copepods and other crustaceans, fish, and squids. They rely heavily on camouflage for protection from predation being a favorite prey of predatory birds, sea lions, billfish, sharks, various tuna, White Seabass, and Yellowtail. Reproduction is via batch spawning with each female releasing between 100,000 and 400,000 eggs per annum with eggs and larvae being pelagic. They have a lifespan of up to 18 years. The Pacific Chub Mackerel is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Pacific Chub Mackerel is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Puerto Vallarta, Jalisco, southward along the west coast of the mainland.
The Pacific Chub Mackerel is easy to identify and cannot be confused with any other species, however, it is virtually identical to the Atlantic Chub Mackerel, Scomber colias (belly with markings), which is found only in the Atlantic Ocean, and is very similar to the Spotted Chub Mackerel, Scomber australasicus (spotting ventrally).
From a conservation perspective the Pacific Chub Mackerel is currently considered to be of Least Concern with stable, widely distributed populations. They are targeted commercially and harvested in purse seines at levels that approach 3,500,000 tons per annum. They are sold fresh, frozen, canned, and pickled for human consumption. They are also canned for pet food and used in Chinese medicine. They are a small highly energetic prized live bait. In the greater Los Cabos area during the months of December, January, and February, they are readily caught by the hundreds utilizing Sabiki Rigs (known locally as “Lucky Joe Rigs”) off the bottom over sandy terrain in deep waters by both recreational anglers and commercial bait salesmen who then sell them to marlin fishermen for $3.00 each. They are also a mainstay of pier fishermen in the greater San Diego area. As an exceptional live bait they are fished fly-lined, slow trolled, or sent down deep with a bottom rig attached to a 7/0 hook.