Bighead Sand Perch, Diplectrum euryplectrum
The Bighead Sand Perch, Diplectrum euryplectrum, whose common Spanish name is serrano extranjero, is a species in the Sea Bass or Serranidae Family, known collectively as serranos in Mexico. Globally, there are twelve species in the genus Diplectrum, ten of which are found in Mexican waters, two in the Atlantic and eight in the Pacific.
The Bighead Sand Perch has an elongated body with an overall grey-brown coloration and white belly. It received its common name from its large (43% of standard length) head. they have a series of characteristic markings including four double dark bars on the sides, two horizontal rows of gold speckles, a large dark spot on the base of the tail, a series of yellow stripes on the head and a purple spot on the gill covers. The head has a wide, squarish bony cheek spur (preoperculum) with 6 to 12 large spines (as pictured below), whose shape is a key to identification. The anal fin is transparent with a very wide yellow-brown stripe, the caudal fin has two very wide yellow-brown stripes and the dorsal fin is grey with a continuous yellow-brown stripe running its length. A key to identification is a dark line at the bottom of the rayous portion of the dorsal fin (as pictured below). They have dusky pectoral and pelvic fins.
The Bighead Sand Perch are found over sandy bottoms at depths between 50 and 400 feet. They reach a maximum length of 21 cm (8.3 inches), documented by a fish that I caught. They are a small, rare, deep water species and not much is known about their behavioral patterns.
In Mexican waters the Bighead Sand Perch are found from Magdalena Bay southward along the southwest coast of the Baja, in the lower third of the Sea of Cortez, and along the coast of the mainland south to Guatemala.
The Bighead Sand Perch is difficult to correctly identify because there are eight very similar looking Sand Perches, all of the Diplectrum Genus, that live in Mexican waters of the Pacific. The key to a correct identification is the unique shape of the preoperclum. See Sand Perch Preoperclum 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.
The Bighead Sand Perch is too small and too rare to be of interest to most.
Bighead Sand Perch, Diplectrum eurylpectrum. Fish caught from coastal waters off Point Palmilla, Baja California Sur, February 2004. Length: 10 cm (3.9 inches). Fish identification courtesy of Dr. Ross Robertson, Smithsonian Institute, Panama.