Mexican Sand Perch, Diplectrum macropoma
The Mexican Sand Perch, Diplectrum macropoma, whose common Spanish name is serrano Mexicano, is a species in the Family Serranidae, the Sea Bass, known as serranos in Mexico. Globally, there are twelve species in the genus Diplectrum, of which ten are found in Mexican waters, two in the Atlantic and eight in the Pacific.
The Mexican Sand Perches have elongated bodies with an overall pale cooper to light brown coloration, a white belly, a series of characteristic markings including two rows of thin dark bars on their sides, a large dark spot at the base of their tail, a series of faint yellow bars under their eyes and a purple spot on their gill covers. Their head has a narrow bony cheek spur (preopercle) with eight to thirteen long spines (pictured below); the shape of their head is a key to identification. All their fins are transparent with the exception of the upper portions of their caudal fin and their pectoral fins, which are yellow. Their anal fin has a very narrow yellow stripe near the edge and their caudal fin has three yellow stripes. Their dorsal fin has a continuous yellow stripe running along its length and a row of spots near the perimeter; these spots are faint in the spiny portion and prominent in the rayed portion of the dorsal fin. A key to identification is dorsal spines one to four, which increase proportionally and stepwise in length.
The Mexican Sand Perches are found over sandy bottoms at depths between 30 and 400 feet. They reach a maximum length of 29 cm (11.3 inches), as documented by a fish that we caught. In Mexican waters they are found from Magdalena Bay south along the Pacific side of Baja, throughout the Sea of Cortez, and along the coastal mainland south to Guatemala. They are a small and rare deep water species and very little is known about their behavioral patterns.
The Mexican Sand Perch is exceedingly difficult to correctly identify because there are eight very similar Sand Perches, all of the Diplectrum Genus, living in Mexican waters of the Pacific. The key to correct identification is the unique shape of their peropercle. Sand Perch Preopercles – for an interesting look at some fish anatomy of some very similar looking fishes of the Diplectrum Genus you can see the preopercles of seven Sand Perches found in the Pacific side-by-side.