Peruvian Flounder, Etropus peruvianus
The Peruvian Flounder, Etropus peruvianus, whose common Spanish name is lenguado zapatilla, is a member of the Sand Flounder or Paralichthyidae Family, known collectively as lenguados areneros in Mexico. Globally there are nine members of the genus Etropus, five of which found in Mexican waters, two in the Atlantic, two in the Pacific, and one in both the Atlantic and the Pacific.
The Peruvian Flounders are left-eyed flat fish with a complete and relatively straight lateral line that starts at the top corner of their gill cover. They have elongated oval bodies with a depth that is 40 to 44% of standard length. Their eye side is tan in color with a large dark blotch behind their gill cover that extends back along their lower flank behind the pectoral fins. Their fins are paler than the body and the outer third of their pectoral fins is dark. Their blind side is off-white. They have a short blunt head with a short small mouth that reaches the front edge of their medium-sized eyes. Their eyes are set close together and parallel. They have 62 to 68 anal rays and 79 to 86 dorsal rays. Their caudal fin has a blunt angular point. Their pectoral fins are 75 to 85% of head length and their pelvic fins originate mid-body. They have 5 to 9 gill rakers on their lower arch and are covered with small rough scales.
The Peruvian Flounders are bottom dwellers found over and within sandy and muddy bottoms at depths up to 150 feet. They reach a 12.3 cm (4.8 inches) in length, as established by a fish that I collected. They are opportunistic and well-camouflaged ambush predators that lie in wait half submerged on the ocean floor.
In Mexican waters the Peruvian Flounders are found in all waters of the Pacific with the exception that they are absent from Magdalena Bay northward along the central and northwest coasts of Baja.
The Peruvian Flounders, although fairly common in some locations, are too small to be of interest to most. They are caught with some frequency as a by-catch of deep water shrimp trawlers.