Chocolate Tonguefish, Symphurus callopterus
The Chocolate Tonguefish, Symphurus callopterus, whose common Spanish name is lengua chocolate, is a species in the Tonguefish or Cynoglossidae Family, known collectively as lenguas in Mexico. There are sixty-six global members of the genus Symphurus, twenty three of which are found in Mexican waters, nine in the Atlantic and fourteen in the Pacific. All members of the family are left eyed fish and the lateral line is absent.
The Chocolate Tounguefish have elongated oval flat bodies that taper to a pointed tail; their width is 28 to 32% of standard length. They have a brown coloration with nine to eleven subtle wide dark bands across their body and a dark blotch on the lower half of their gill cover. The rear portions of their anal and dorsal fins have ten to nineteen rectangular black blotches alternating with clear areas. Their caudal fin is black or with black blotches. Their ventral or blind side is cream color. Their head has a rounded snout with a small curved mouth and small beady eyes on the left side closely set together with the upper eye being slightly in front of the lower eye. Their anal and dorsal fins are confluent with the pointed caudal fin. Their anal fin has 91 to 98 rays. Their dorsal fin originates above the upper eye and has 105 to 114 rays. They only have a left pelvic fin, no pectoral fins, and no lateral lines. Their body is covered with rough scales.
The Chocolate Tonguefish are found over and within soft sandy and muddy bottoms at depths between 65 and 950 feet. They are uniquely colored to blend with the substratum. They reach a maximum length of 16.2 cm (6.4 inches). They feed on small fish and crustaceans.
The Chocolate Tonguefish has a limited range in Mexican waters of the Pacific being found from Magdalena Bay to Cabo San Lucas along the southwest coast of Baja and from Mazatlán south to Guatemala along the coast of the mainland.
The Chocolate Tonguefish can be confused with the Halfspotted Tonguefish, Symphurus atramentatus, the Banded Tonguefish, Symphurus fasciolaris, and the Whitetail Tonguefish, Symphurus oligomerus, however each of these lack the blotching pattern at the base of their anal and dorsal fins.
The Chocolate Tonguefish are small and seldom seen by humans, thus of limited interest to most.