Jack Mackerel, Trachurus symmetricus

Jack Mackerel, Trachurus symmetricus. Fish provided by the commercial fishermen of the greater San Diego area, San Diego, California, November 2014. Length: 20 cm (7.9 inches).

Jack Mackerel, Trachurus symmetricus. Fish caught from coastal waters off Santa Cruz, California, September 2023. Length: 22 cm (8.7 inches). Catch, photograph and identification courtesy of Ben Cantrell, Peoria, Illinois.

Jack Mackerel, Trachurus symmetricus. Fish caught from coastal waters off Santa Cruz, California, May 2016. Length: 25 cm (10 inches). Catch, photograph and identification courtesy of Andrew Hansen, Santa Cruz, California.

Jack Mackerel, Trachurus symmetricus. Fish caught from coastal waters off Auckland, New Zealand, August 2014. Length: 28 cm (11 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Jack Mackerel, Trachurus symmetricus. Underwater photograph taken in coastal waters off La Jolla, California, September 2017. Photograph courtesy of Bob Hillis, Ivins, Utah.

The Jack Mackerel, Trachurus symmetricus, is a member of the Jack or Carangidae Family, that is also known as the Pacific Jack Mackerel and in Mexico as charrito chicharo; in the greater Los Cabos area they are one of the four fish that are known as Chi-willie. There are twenty global members of the genus Trachinotus, of which seven are found in Mexican waters, three in the Atlantic and four in the Pacific Ocean.

The Jack Mackerel has a “mackerel-like” elongated slender modestly compressed body that has a depth that is 17% to 21% of standard length. They are metallic blue to olive green in color and their lower two-thirds are paler ranging from white to silver. They have a black spot on the upper edge of their gill cover. Their head is pointed and features large eyes with fatty eyelids. Their anal fin has two standalone spines followed by 1 spine and 24 to 36 rays; their caudal fin base is slender and the fin “V” sharped and is deep and wide; their first dorsal fin has 8 spines; their second dorsal fin has 1 spine and 29 to 32 rays; and, their pectoral fins are long reaching past the anus. Their anal and second dorsal fins have long bases and are similar in appearance, however, the anal fin is slightly shorter. They do not have isolated finlets. A key to identification is their lateral line, which is arched in the middle and has well developed scutes on both curved and straight parts. Their body is covered with scales.

The Jack Mackerel is a coastal schooling pelagic species found from the surface in the surf zone to depths of 402 m (1,320 feet). They reach a maximum length of 81 cm (2 feet 8 inches). As of January 1, 2024, the International Game Fish Association world record stood at 0.57 kg (1 lb 4 oz) with the fish caught in coastal waters off Santa Catalina Island, California, in April 2017. The Jack 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 Jack Mackerel is a resident of Mexican waters of the Pacific but has a limited range being found along the entire west coast of Baja and from Santa Rosalia, Baja California Sur, southward along the central and southeast coasts of the Baja.

The Jack Mackerel is very easily confused with the three Mackerel Scads of the Decapterus Genus found in Los Cabos waters of Baja California Sur: the Amberstripe Scad, Decapterus muroadsi, the Mackerel Scad, Decapterus macraellus, and the Shortfin Scad, Decapterus macrosoma (all of which have less prominent scutes on their lateral line and less pronounced arches of the lateral line). All four are known as Chi-willie by local Mexican fishermen.

From a conservation perspective the Jack Mackerel is currently considered to be of Least Concern with stable, widely distributed populations. I catch Jack Mackerel at certain times of year out of rather deep water on cut squid or yo-yo iron with larger individuals being a strong foe on light tackle. I have also caught them with hand lines and small treble hooks during predawn hours off the surface well out at sea at a rate of 2 dozen per hour chummed in with cut Skipjack Bonito; however, the bite will stop with daylight. They readily survive bait tanks and are a favorite of local Pangueros, who use them as a slow-trolled live bait targeting Dorado, Sailfish, and the elusive Wahoo during the fall season. They can also be used as a cut bait for bottom fishing. They are retained for table fare if nothing else is available as a “take home.”