Mexican Moonfish, Paraselene orstedii

Mexican Moonfish, Paraselene vomer. Fish caught from coastal waters off Puerto Chomes, Costa Rica, March 2021. Length: 26 cm (10 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Mexican Moonfish, Paraselene orstedii, is a member of the Jack or Carangidae Family, that is also known as the Hairfin Lookdown and in Mexico as jorobado carite. Globally, there are nine species in the genus Selene, of which six are found in Mexican waters, three in the Atlantic and three in the Pacific Ocean.

The Mexican Moonfish has a short strongly compressed pentagonally shaped very deep body that is 64% to 68% of standard length. They are uniformly silver in color with metallic blue-green tint. The juveniles are yellowish with four or five interrupted, dark, transverse bars. Their head has a very steep straight forehead profile with a rounded forehead and a pointed snout. Their mouth is small and opens in the front and ends well before the eyes. Their anal fin has 2 standalone spines followed by 1 spine and 17 to 20 rays with an elongated lobe that are greatly elongated in juveniles; their caudal fin has a slender base and is deeply forked; their first dorsal fin has 8 short spine the first one being isolated; their second dorsal fin has 1 spine and 17 to 20 rays with an elongated lobe that are greatly elongated in juveniles; their pectoral fins are long and curves; and, their pelvic fins are elongated in juveniles but are short in adults. They have 14 to 17 gill rakers on the first arch. Their body is covered with very small scales but appears scaleless. Their lateral line has a series of small weak scutes.

The Mexican Moonfish is a pelagic schooling species that is found in shallow coastal waters in small schools near the bottom over sandy and hard substrate at depths up to 50 m (165 feet). The juveniles frequent estuaries. They reach a maximum of 33 cm (13 inches) in length. They consume small crabs, small fishes and polychaete worms. The Mexican Moonfish 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 Mexican Moonfish is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from the northern two-thirds of the Sea of Cortez and from Magdalena Bay northward along the central and northwest coasts of Baja.

The Mexican Moonfish can be easily confused with the Mexican Lookdown, Selene brevoortii (very high concave foreheads; minute pelvic fins) and the Pacific Moonfish, Selene peruviana (oval body; short concave foreheads; minute pelvic fins).

From a conservation perspective the Mexican Moonfish is currently considered to be of Least Concern with stable, widely distributed populations. They are considered to be a good human food fish that are targeted by artisanal fishermen with gill nets. They are also pursued by recreational anglers.