Kawakawa, Euthynnus affinis
Kawakawa, Euthynnus affinis. Fish caught from coastal waters off Maafushi, Maldives, December 2017. Length: 66 cm (2 feet 2 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Kawakawa, Euthynnus affinis, is a member of the Mackerel or Scombridae Family, that is also known as the Little Tuna, the Mackerel Tuna and the Wavyback Tuna and in Mexico as bacoreta oriental. Globally, there are three species in the genus Euthynnus, and all three are found in Mexican waters, one in the Atlantic and two in the Pacific Ocean.
The Kawakawa has an elongated fusiform medium sized tuna-like body. They are dark blue dorsally and transition to silver ventrally. They have a patch of 12 broken oblique stripes on their back that do not extend past the middle of their dorsal fin. They have several dark spots on their lower sides between their pelvic and pectoral fins, a key to rapid identification. They have small black eyes and conical teeth. Their anal fin has 11 to 15 rays and 6 to 8 finlets; their caudal fin is large and crescent-shaped with 2 small keels separated by 1 large keel at the base with a very slender peduncle; their first dorsal fin has 10 to 15 spines and the anterior spines are much longer than midway, giving it a concave appearance; their second dorsal fin has 11 to 15 spines, and is much lower than the first, and has 8 to 10 finlets; their pectoral fins are short; and, their pelvic fins are below the base of the pectoral fins. They have 29 to 34 gill rakers on the first arch. They have a limited number of scales.
The Kawakawa is a highly migratory pelagic species found from the surface to depths 1.10 m (3 feet 7 inches) in length and 14 kg (31 lbs) in weight. The juveniles are known to enter bays and harbors. As of March 31, 2023, the International Game Fish Association world record for length stood at 75 cm (2 feet 6 inches) with the fish caught from coastal waters off Australia in March 2017. As of March 31, 2023, the International Game Fish Association world record for weight stood at 15.05 kg (33 lbs 3 oz) with the fish caught from coastal waters off Molokai, Hawaii in June 2014. They travel in large multi-species schools of Bullet Mackerel, Auxis rochei, Frigate Mackerel, Auxis thazard, Skipjack Tuna, Katsuwonus pelamis, Torpedo Scad, Megalaspis cordyla, and Yellowfin Tuna, Thunnus albacares, comprised of between 100 and 5,000 or more individuals. They are non-selective, highly opportunistic omnivores that consume fishes, crustaceans, squid and zooplankton. In turn they are preyed upon by marlins and sharks. Juvenile fish have a sex ratio of 1:1; with maturity, the males will dominate adult populations. Reproduction involves batch spawning with each female releasing between 210,000 and 680,000 in each session and 2,500,000 annually. They have live spans of six years. The Kawakawa 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 Kawakawa is found predominantly within the Indo-Pacific. In Mexican waters their range is limited to the coastal waters of Baja California and the Revillagigedo Islands in the Pacific.
The Kawakawa is very similar to and easily confused with the Black Skipjack, Euthynnus lineatus (5 or 6 stripes just below the dorsal fin that extend well past the dorsal fin).
From a conservation perspective the Kawakawa is currently considered to be of Least Concern, with stable widely distributed populations. They are heavily targeted by both commercial and recreational fishermen in many parts of their range. They are caught commercially at annual levels of 300,000 tons, with gill nets and purse seines predominately in the Indio-Pacific. They are sold canned, fresh and frozen for human consumption. They are known to have a short shelf life and there are reports that they contain ciguatera toxin. They are utilized extensively by the pet food industry.