Keeltail Needlefish, Platybelone argalus

Keeltail Needlefish, Platybelone argalus. Fish collected off the beach alive at Cabo Real, Baja California Sur, March 2019. Length: 35 cm (14 inches).

Keeltail Needlefish, Platybelone argalus. Fish caught from coastal waters off Puerto Rico, August 2014. Length: 35 cm (14 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

The Keeltail Needlefish, Platybelone argalus, is a member of the Needlefish or Belonidae Family, and known in Mexico as agujón de quilla. Globally, there are seven species in the genus Platybelone, of which one, this species, which is found in Mexican waters of both the Atlantic and the Pacific Oceans.

The Keeltail Needlefish are one of the more exotic and unique fishes of Mexico. They have an extremely elongated cylindrical body that is greenish blue on the upper back and abruptly transitions to silvery well above the mid-body. They have very long beaks (25% to 27% of standard length) and their lower jaw is significantly longer than their upper jaw. They have small teeth. Their caudal base is flattened with a large lateral keel, after which they are named, that is at least three times wider than it is deep; their caudal fin is slightly forked with the lower lobe being slightly larger than the upper lobe; and, their pectoral and pelvic fins are short.

The Keeltail Needlefish is an oceanic pelagic fish found in the first 5 m (15 feet) of the water column. They reach a maximum length of 50 cm (20 inches). The Keeltail Needlefish is a very rare species and 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 Keeltail Needlefish is a resident of Mexican waters of both the Atlantic and the Pacific Oceans. They are found in all waters of the Atlantic Ocean. In the Pacific they have a limited distribution being found from San Quintin, Baja California, southward along the northwest, central and southwest coasts of Baja, in the southern half of the Sea of Cortez, and along the coast of the mainland from Acapulco, Guerrero, southward to Guatemala.

Due to the unique shape of their tail base and to their elongated slender body, the Keeltail Needlefish cannot be confused with any other Needlefish.

From a conservation perspective the Keeltail Needlefish is currently considered to be of Least Concern with stable, widely distributed populations. In general they are too small in stature to be of interest to most however they are utilized as a food fish by some cultures.