Spotted Chub Mackerel, Scomber australasicus
Spotted Chub Mackerel, Scomber australasicus. Fish caught from coastal waters off Sydney, Australia, September 2016. Length: 10 cm (3.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
Spotted Chub Mackerel, Scomber australasicus. Fish caught from coastal waters off Wollongong, NSW, Australia, January 2020. Length: 30 cm (12 inches). Catch, photograph, and identification courtesy of Kenneth Tse, Toronto, Canada.
The Spotted Chub Mackerel, Scomber australasicus, is one of the most common members of the Mackerel or Scombridae Family, that is also known as the Blue Mackerel and in Mexico as macarela pintoja. 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 Spotted Chub Mackerel has an elongated, rounded, fusiform, and tuna-like body that is designed aerodynamically for speed. They are blue-gray dorsally with numerous zigzag lines along the back and upper caudal base. Ventrally they are pearly white with thin undulating wavy broken lines. Their head has a pointed snout and large black eyes that are covered with adipose eyelids at the front and rear. The mouth has teeth present on the roof. Their anal fin has 12 rays, and is found behind the origin of the second dorsal fin, and is followed by 5 finlets; their caudal fin is deeply forked with 2 small keels at the slender tail base; their first dorsal fin has 10 to 13 spines; their second dorsal fin has 12 rays followed by 5 finlets and is found in front of the second dorsal fin; and, their pectoral fins are found high on the body and are short. They are covered with small scales. Their lateral line runs the entire length of the body.
The Spotted Chub Mackerel is a pelagic found in both coastal and oceanic waters. They form large schools that can number up to tens of thousands of individuals that include Jack Mackerels, Trachurus symmetricus and Pacific Sardines, Sardinops sagax. They are found from the surface to depths up to 200 m (660 feet). They are fast growing, reaching a maximum of 44 cm (17 inches) in length and 1.4 kg (3 lbs 2 oz) in weight. As of January 1, 2023, the International Game Fish Association world record stood at 2.14 kg (4 lbs 11 oz) with the fish caught in coastal waters off New Zealand in November 2011. They are vertical migrators (diel migration) that are found in the open ocean at night and on the bottom during the day. They also undergo seasonal migrations residing in waters that are between 8oC (46oF) and 12oC (53oF), moving to cooler waters during the summer and returning during the winters. They filter small crustaceans from the water column but are also a voracious and indiscriminate carnivore consuming anchovies, krill and microscopic plankton. In turn they are preyed upon by billfish, sharks, tunas, and other fish and marine mammals including sea lions and various sea birds and rely heavily on camouflage for protection. Reproduction is oviparous with batch spawning occurring in several small batches with each female releasing between 100,000 and 400,000 eggs annually. Their eggs and larvae are pelagic. They have live spans of up to twenty-four years.
The Spotted Chub Mackerel is easily confused with Pacific Chub Mackerel, Scomber japonicus (9 or 10 dorsal spines; no markings ventrally).
The Spotted Chub Mackerel are common in the sub-tropical waters of the Western Indio-Pacific. In Mexican waters they have a very limited distribution being found only off the Revillagigedo and Socorro Islands.
From a conservation perspective the Spotted Chub Mackerel is currently considered to be of Least Concern with overall stable, widely distributed populations. They are caught at a level of 300,000,000 to 500,000,000 tons annually via encircling nets and purse seines. Spotted Chub Mackerel are consumed by humans smoked, grilled or broiled. They are utilized as meat binders added to meat products to keep the meat and seasoning bound tightly together lowering costs and enhancing flavor and texture of the product. They are also used in cat food. For recreational anglers they are caught on dead cut base and lures. They are utilized as a live bait targeting tuna and other large game fish.