Threadfin Jack, Euprepocaranx dorsalis
Threadfin Jack, Euprepocaranx dorsalis, Juvenile. Fish provided by commercial bait salesmen based out of Puerto Los Cabos, Baja California Sur, June 2015. Length: 21 cm (8.3 inches).
Threadfin Jack, Euprepocaranx dorsalis, Juvenile. Fish caught from coastal waters off Mazatlán, Sinaloa, October 2017. Length: 22 cm (8.7 inches). Photograph courtesy of Jason Potts, Mazatlán, Sinaloa.
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters off Puerto Adolfo Lopez Mateos, Baja California Sur, February 2017. Length: 28 cm (11 inches). Catch, photograph and identification courtesy of Brad Murakami, Surrey, British Columbia, Canada.
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters off Las Barilles, Baja California Sur, April 2020. Length: 36 cm (14 inches). Catch, photograph and identification courtesy of Chip Shapley, Los Barriles.
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters of Puerto Los Cabos, Baja California Sur, February 2001. Length: 40 cm (16 inches).
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters off Loreto, Baja California Sur, July 2024. Length: 42 cm (17 inches). Catch and first and second photographs courtesy of Servando Davis, Loreto. Third photo of “small dark blotches between the bases of the dorsal rays” a key to the identificaiton.
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters off Key Largo, Florida, January 2014. Length: 46 cm (18 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.
Threadfin Jack, Euprepocaranx dorsalis. Fish caught from coastal waters off the San José Rió Boca, San José del Cabo, Baja California Sur, June 2021. Length: 66 cm (2 feet 2 inches).
The Threadfin Jack, Euprepocaranx dorsalis, is one of the rarer members of the Jack or Carangidae Family, that is also known as the Thread Pompano and in Mexico as jurel chicuaca. This is the only member of the genus Euprepocaranx, which is found in Mexican waters of the Pacific Ocean.
The Threadfish Jack has a deep compressed diamond-shaped oblong body with a depth that is 39% to 61% of standard length; their body becomes more elongated with age. They are overall silvery-gray in color and have an elongated black spot on top of their gill cover. They have small dark blotches between the bases of their dorsal fin rays, a key to the identification. They have an angular head profile. Their anal fin two standalone spines followed by 1 spine and 16 or 17 rays; their caudal fin has a slender base and is deeply forked; their first dorsal fin has 8 spines; their second dorsal fin has 18 or 19 rays; their pectoral fins are long; and, their pelvic fins are small. The anal and first dorsal fin is filamentous and elongated. They have 15 to 17 gill rakers on the upper arch and 21 to 23 gill rakers on the lower arch. Their body is covered with small scales except for a long continuous scale-free area on their breast and pectoral fin base. Their lateral line is broadly arched (curved portion equal in length to the arched portion) with 40 to 53 small but highly visible scutes.
The Threadfin Jack is a coastal pelagic species found at depths up to 100 m (330 feet). They reach a maximum of 67 cm (2 feet 2 inches) in length. They are opportunistic predators feeding on benthic and pelagic fish as well as squid and crustaceans. The Threadfin Jack is 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 Threadfin Jack is a resident of Mexican waters of the Pacific Ocean but with a limited distribution being found from Guerrero Negro, Baja California, southward along the central and southwest coasts of Baja, in the southern three-fourths of the Sea of Cortez, and along the coast of the mainland south to Guatemala.
The Threadfin Jack is very similar to and very difficult to differentiate from the African Pompano, Alectis ciliaris (blunter snout; scale-free body; juveniles with multiple extremely long anal and dorsal fin rays).
From a conservation perspective the Threadfin Jack is currently considered to be of Least Concern with stable, widely distributed populations. Although exceedingly rare they are considered good table fare. I have only seen them marketed fresh on one occasion in the fish markets of the greater Los Cabos area of Baja California Sur.