Bullet Mackerel, Auxis rochei
Bullet Mackerel, Auxis rochei. Fish caught off Point Palmilla, Baja California Sur, November 2015. Length: 25 cm (9.8 inches).
Bullet Mackerel, Auxis rochei. Fish caught from coastal waters off Loreto, Baja California Sur, April 2015. Length: 26 cm (10 inches). Catch, photograph, and identification courtesy of Chris Wheaton, Fullerton, California.
The Bullet Mackerel, Auxis rochei, is one of the most common members of the Mackerel or Scombridae Family, that is also known as the Bullet Tuna, and in Mexico as melvera and bolito. Globally, there are two species in the genus Auxis, this species found in Mexican waters of the Pacific and a second species found in Mexican waters of both the Atlantic and the Pacific Oceans. The Bullet Mackerel found in Mexican waters of the Pacific is actually the subspecies Auxis rochei eudorax.
The Bullet Mackerel has a robust elongated rounded fusiform tuna-like body. They are torpedo-shaped with no fins and are designed aerodynamically for speed. Dorsally, they are dark bluish with fifteen or more fairly broad nearly vertical bars above their lateral line; ventrally, they are silvery white. They have mid-sized black eyes and slender conical teeth. Their anal fin is small with 12 to 14 rays and 7 finlets; their caudal fin is deeply forked with 2 small keels separated by 1 large keel at the base; their first dorsal fin has 9 to 12 spines followed by 8 finlets; their second dorsal fin is widely separated from the first, and is small with 10 to 13 rays and followed by 8 finlets; and, their pectoral fins are short. The front portion of their body is covered with scales. The Bullet Mackerels are a global pelagic highly migratory species found in both oceanic and coastal waters at depths up to 200 m (655 feet). They reach a maximum of 55 cm (22 inches) in length and 1.8 kg (4 lbs 0 oz) in weight. As of January 1, 2023, the International Game Fish Association world record stood at 1.84 kg (4 lbs 1 oz) with the fish caught in coastal waters off Spain in July 2004. They normally travel in large schools at times mixed in with the Frigate Mackerel or Frigate Tuna, Auxis thazard. Each female releases between 31,000 and 103,000 eggs annually with the eggs and larvae being pelagic. The larvae from the two species of Auxis are the most abundant of all tuna larvae. Due to their abundance they are considered an important component of the oceanic food web, particularly as food for larger fish. They feed on small fish, crustaceans, and squids. They have lifespans of five years. The Bullet 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 Bullet Mackerel is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from of the northern half of the Sea of Cortez.
The Bullet Mackerel is very similar to and can be very easily be confused with the Frigate Mackerel, Auxis thazard (15 or more broad oblique to oblique bars beginning under the first dorsal and pectoral fins).
From a conservation perspective the Bullet Mackerel are currently considered to be of Least Concern, with stable, widely distributed populations. They are considered an important commercial catch in certain parts of the world being caught by hook and line and as a by-catch in gill nets, purse seines, and traps at a level of 250,000 tons per year. They are marketed fresh, frozen, dried and salted, and smoked and canned. In the greater Los Cabos area they are an incidental catch on rapidly trolled feathers or hoochies or on fly-lined Flatiron Herring. They are used on a limited basis as fly-lined bait fish, chunk bait, or cut bait for fishing down deep.