Sand Perch, Diplectrum formosum
The Sand Perch, Diplectrum formosum, whose common Spanish name is serrano arenero, 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. This is one of the two sand perches found in the Atlantic Ocean and is by far the largest.
The Sand Perches have elongated slender slightly compressed bodies with very similar dorsal and ventral profiles. They are pale brown on the back and sides, fading to white ventrally. They have five to seven vertical bars that are yellowish-brown to tan. They also have a conspicuous dark mid-body stripe, ending in a dark spot on the upper half of their caudal fin base. They have the ability to change this stripe color from pale to dark very quickly. They have bright blue lines across their head and body and some individuals have orange and blue shading on their sides. All their fins are dusky with the caudal fin also having light orange blotches and the dorsal fin having longitudinal blue and yellow lines. Their head, eyes, and mouth are large. Their preoperclum has two clusters of numerous sharp long spines. Their anal fin has 3 spines and 7 or 8 soft rays; their caudal fin is concave with the upper lobe being larger than the lower lobe; their dorsal fin has a long base with 10 spines and 12 rays and is continuous without a notch; and their pelvic fins are long and originate before or under the pectoral fins.
The Sand Perches are found in shallow bays within seagrass beds at depths up to 660 feet. They reside in holes in sandy bottoms or under rocks. They reach a maximum length of 30 cm (12 inches). They feed primarily on benthic crustaceans including amphipods, crabs, and shrimps as well as small fish. They are preyed upon by larger fish and are an important food source for drums, groupers, porgies, sharks, snappers, and various sea birds. They spawn in deep water as mating pairs with each fish being synchronously hermaphroditic possessing both males and female organs and producing eggs and sperm at the same time. The eggs and larvae are pelagic and move to shallow waters as they mature. They are a non-schooling species with lifespans of six to seven years.
In Mexican waters the Sand Perch are found in waters of the Atlantic.
The Sand Perch can be confused with the Dwarf Sand Perch, Diplectrum bivittatum (only one set of spines on preoperclum; triangular black spot on upper gill cover; irregular vertical dark bars on sides).
The Sand Perches are fished commercially and recreationally although they give a poor fight due to their small size. They are considered an excellent food fish. They are also used as live bait for larger fish. They are caught by hook and line on cut bait from shores, bridges, and small boats and are unfriendly towards divers.