Moustache Jawfish, Opistognathus lonchurus

Moustache Jawfish, Opistognathus lonchurus. Fish caught from coastal waters off Ft. Lauderdale, Florida, February 2022. Length: 9.8 cm (3.9 inches). Catch, photograph and  identification courtesy of Dominick Porcelli, Lighthouse Point, Florida.

The Moustache Jawfish, Opistognathus lonchurus, is a member of the Jawfish or Opistognathidae Family, that is known in Mexico as bocón bigote. Globally, there are forty-three species in the genus Opistognathus, of which thirteen are found in Mexican waters, six in the Atlantic and seven in the Pacific Ocean.

The Moustache Jawfish have an elongated compressed tapering body with a large bulbous head. Their eyes are large and set high on the head and their mouth is large and terminal that extends to the rear of the eyes. They are yellowish-brown with blue lips and iris and a blue stripe along the cheek onto the gill cover. They have two thin pale blue stripes along the mid-flank that extends from the gill cover to the base of the caudal fin and a second blue line along the upper body. Their anal and dorsal fins are pale orange with blue stripes along their bases, edges and centers; their caudal fin has orange-yellow rays with blue membranes in between the rays and blue margins. Their anal has 3 spines and 12 or 13 rays and a long base; their caudal fin is rounded; their dorsal fin has 11 spines and 12 or 13 rays and a long base; and, their pelvic fins are short and have 1 spine and 5 rays with the outer 2 being strong and branched and the inner 3 weaker and branched and occur before pectoral fins. They have 34 to 62 gill rakes. They are covered with smooth small scales. Their lateral line is only on the front half of the body.

The Moustache Jawfish is found within fine sediment mixed with some coarse materials in burrows, which it enters tail first, at depths between 10 m (33 feet) and 100 meters (330 feet). They reach a maximum of 15 cm (5.9 inches) in length. The juveniles are found in shallower waters than the adults. Unhatched fish are mouth brooded by the males. Their larval stage is short and the juveniles are prone to predation and they utilized burrowing to avoid predation. The Moustache Jawfish 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 Moustache Jawfish is most like confused with the only Jawfish found in Mexican waters of the Atlantic Ocean, the Yellowhead Jawfish, Opistognathus aurifrons (yellow head).

The Moustache Jawfish is a resident of Mexican waters of the Atlantic Ocean, but its range and distribution has been very poorly documented.

From a conservation perspective, the Moustache Jawfish is currently considered to be of Least Concern, with stable, widely distributed populations. They are small in stature, a relatively deep-water species and are seldom seen by humans. They are utilized by the aquarium trade at a minimal level.