Mexican Sand Perch, Diplectrum macropoma

Mexican Sand Perch, Diplectrum macropoma. Fish caught from coastal waters off Point Palmilla, Baja California Sur, January 2015. Length: 14 cm (5.5 inches).

Mexican Sand Perch, Diplectrum macropoma: preoperculum.

Mexican Sand Perch, Diplectrum macropoma. Fish caught from coastal waters off Puertoecitos, Baja California, November 2014. Length: Cabo San Lucas, Baja California Sur, January 2015. Length: 10 cm (3.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Mexican Sand Perch, Diplectrum macropoma, is a member of the Sea Bass or Serranidae Family, and is known in Mexico as serrano Mexicano. 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 Ocean.

The Mexican Sand Perch has an elongated body with an overall pale cooper to light brown coloration, a white belly, a series of characteristic markings including 2 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 (preoperculum) with 8 to 13 long spines (pictured below); the shape of their preoperculum 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 3 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 are dorsal spines one to four that increase proportionally and stepwise in length.

The Mexican Sand Perch is found over sandy bottoms at depths between 10 m (30 feet) and 121 m (400 feet). They reach a maximum of 29 cm (11.3 inches) in length, as documented by a fish that I caught. The Mexican Sand Perch are synchronously hermaphroditic possessing both males and female organs and capable of producing eggs and sperm at the same time. They spawn in deep water as mating pairs. Their eggs and larvae are pelagic and move to shallower waters as they mature. The Mexican Sand Perch 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 Mexican Sand Perch is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Magdalena Bay, Baja California Sur, southward along the southwest coast of Baja, throughout the Sea of Cortez, and along the coastal mainland south to Guatemala.

The Mexican Sand Perch is difficult to correctly identify because there are 8 very similar Sand Perches, all of the Diplectrum Genus, living in Mexican waters of the Pacific Ocean. The key to a correct identification is the unique shape of the preoperclum. See Sand Perch Preoperculum for an interesting side-by-side look at some fish anatomy of seven very similar looking fishes of the Diplectrum Genus found in the Pacific Ocean.

From a conservation perspective the Mexican Sand Perch is currently considered to be of Least Concern with stable widely distributed populations. They are uncommon in the greater Los Cabos area of Baja California Sur. They are too small and too rare to be of interest to most.