Blackfin Jack

Blackfin Jack, Hemicaranx zelotes

The Blackfin Jack, Hemicaranx zelotes, whose common Spanish name is jurelito chocho, is a member of the Jack or Carangidae Family, known collectively as jureles and pámpanos in Mexico. Globally, there are four species in the genus Hemicaranx, all of which found in Mexican waters, two in the Atlantic and two in the Pacific.

The Blackfin Jacks have “jack-like”, moderately compressed, oval, and fusiform bodies with a depth that is 35% to 39% of standard length. They are silvery blue dorsally and transition to silvery white ventrally. Juveniles have four or five bars on their sides. Their head and snout are black. They have a large black area on their pectoral fin axis. Their fins are dark. Their head is small with a blunt rounded snout. They have a small mouth with a slightly projecting lower jaw that does not reach their moderately large eyes. They are equipped with a single series of small close-set teeth on each jaw. Their anal fin has one spine and 22 to 25 rays; their caudal fin is wide and forked with a longer upper lobe; their first dorsal fin is low and preceded by an antrose spine, and has seven or eight spines; their second dorsal fin is similar to the anal fin and has one spine and 25 to 31 rays; and their pectoral fins are long and reach the anal fin origin. They have seven to ten plus 18 to 23 gill rakers and 47 to 55 strong well-developed scutes. Their lateral line is strong with a short and pronounced high anterior arch. Their body is covered with small scales.

The Blackfin Jacks are a benthopelagic schooling species found in coastal waters at depths up to 100 feet. They are known to enter brackish waters. They reach a maximum length of 35 cm (14 inches). They are opportunistic predators and feed on benthic and pelagic fish as well as squid and crustaceans. They are a poorly studied species and very little is known about their behavioral patterns.

In Mexican waters the Blackfin Jacks are found from Magdalena Bay southward along the southwest coast of Baja, in the lower half of the Sea of Cortez, and southward along the coast of the mainland to Guatemala.

The Blackfin Jacks can be confused with the Whitemouth Jack, Uraspis helvola (oblong body; inside of mouth white) and the Yellowfin Jack, Hemicaranx leucurus (yellow fins).

The Blackfin Jacks are of minor commercial importance. They are caught as a by-catch by shrimp trawlers and in gill nets and marketed fresh and salted or dried on a limited basis. From a conservation perspective they are considered of Least Concern being widespread and abundant in certain locations with stable populations.

Blackfin Jack, Hemicaranx zelotes. Fish caught from coastal waters of Magdalena Bay, Baja California Sur, May 2017. Length: 27 cm (11 inches). Catch courtesy of Jimmy Camacho, Puerto Adolfo Lopez Mateos. Identification courtesy of H.J. Walker, Jr., Scripps Institute of Oceanography, La Jolla, CA.

Blackfin Jack, Hemicaranx zelotes. Fish caught from coastal waters of Magdalena Bay, Baja California Sur, August 2017. Length: 27 cm (11 inches). Identification courtesy of H.J. Walker, Jr., Scripps Institute of Oceanography, La Jolla, CA.