Gulf Sanddab, Citharichthys fragilis
Gulf Sanddab, Citharichthys fragilis. Fish courtesy of the commercial fishermen of Bahía Kino, Sonora, March 2015. Length: 22.5 cm (9.0 inches). Photograph and identification courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora.
The Gulf Sanddab, Citharichthys fragilis, is a member of the Sand Flounder or Paralichthyidae Family, and is known in Mexico as lenguado flaco. Globally, there are twenty-four species in the genus Citharichthys, of which sixteen are found in Mexican waters, eight in the Atlantic and eight in the Pacific Ocean.
The Gulf Sanddab is a flatfish that has an elongated narrow body that tapers toward the tail with a body depth is 34 to 38% of standard length. Their dorsal side is brown with darker brown mottling and scattered bluish spots. Their fins are paler than the body. Their blind slide is off-white to tan. They quickly fade to a uniform brown color upon collection. Their head is relatively short with a medium-sized mouth that ends under the center of the lower eye. Their large eyes are on the left side and separated with the lower eye preceding the upper eye. They have one series of immovable teeth on each jaw and no canines. Their anal fin has 61 to 73 rays; their caudal fin is slightly rounded; their dorsal fin has 76 to 92 rays; and, their pectoral fin has 10 to 12 rays. They have 14 to 21 long slender gill rakers on their lower arch. Their body is covered with mid-sized rough scales on both sides and their lateral line is straight running from the gill covers to the caudal peduncle.
The Gulf Sanddab is a demersal species that is found over sandy and muddy bottoms in bays and estuaries at depths between 18 m (60 feet) and 350 m (1,140 feet). They reach a maximum of 25.0 cm (9.8 inches) in length. They consume a wide variety of crustaceans and small fish. In turn they are preyed upon by various marine mammals, larger fish, and sea birds. They are masters at camouflage and can rapidly change colors to match their substrate. The Gulf Sanddab 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 Gulf Sanddab is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from along the coast of the mainland from Mazatlán, Sinaloa south to Guatemala.
The Gulf Sanddab can be easily confused with the Beach Flounder, Syacium latifrons (7 or 8 lower gill rakers), the Bigmouth Sanddab, Citharichthys gilberti (deep oval body), the Five-Rayed Sanddab, Citharichthys mariajorisae (15 to 17 lower gill rakers), and the Pacific Sanddab, Citharichthys sordidus (deep oval body).
From a conservation perspective the Gulf Sanddab is currently considered to be of Least Concern with stable widely distributed populations. They are small in stature and too rare to be of interest to most. They are a minor by-catch of deep water trawlers.