Bridled Sand Perch, Diplectrum rostrum
The Bridled Sand Perch, Diplectrum rostrum, whose common Spanish name is serrano frenado, 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 Bridled Sand Perches have long slender bodies with an overall tan color, a white belly, and a head covered with yellow-orange stripes. Their head features a narrow bony cheek spur (preopercle) with seven to eleven spines (pictured below); the shape of their head is a key to identification. They have five to seven dark bars on their sides, an indistinct black mid-lateral stripe, two black spots at the base of their symmetrical tail fin, two pink bars and a yellow ring under their eyes, and a gray tail with clear spots.
The Bridled Sand Perches are found over sandy bottoms at depths between 50 and 250 feet. They reach a maximum length of 26 cm (10.4 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, the southern half of 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 Bridled 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 preopercle as presented below. 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.
The Bridled Sand Perch is too small and too rare to be of interest to most.