Longfin Sanddab, Citharichthys xanthostigma

Longfin Sanddab, Citharichthys xanthostigma. Fish caught from coastal waters off San Diego, California, December 2020. Length: 22 cm (8.7 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.

Longfin Sanddab, Citharichthys xanthostigma. Fish caught from coastal waters off Huntington Beach, California, January 2020 by Mike Ortiz, Anaheim, California. Photograph and identification courtesy of Chris Wheaton, Fullerton, California.

The Longfin Sanddab, Citharichthys xanthostigma, is a member of the Sand Flounder or Paralichthyidae Family, that is known in Mexico as lenguado alón. Globally, there are twenty-four members of the genus Citharichthys, of which sixteen are found in Mexican waters, eight in the Atlantic and eight in the Pacific Ocean.

The Longfin Sanddab is a flatfish with an elongated oval body with a depth that is 43% to 48% of standard length. Their eye side is a light olive brown to dark brown color speckled with orange and white. Their blind slide is off-white to tan. Their pectoral fins have faith dusky to black crossbars. They have five rows of ocelli that have yellow centers and blackish borders, two randomly spaced about the lateral line, one along the lateral line, and two below the lateral line that are paired. They are masters at camouflage having the ability to change colors to match their substrate. Upon collection they quickly fade to a uniform brown color. Their head is short and blunt with the large eyes on the left side set close together. The front edge of the lower eye is a little in front of the front edge of the upper eye. Their mouth is mid-sized, ends under the first half of the lower eye, and is equipped with one series of immovable teeth on each jaw; they lack canines but the front teeth are enlarged. Their anal fin has 61 to 69 rays; their caudal fin is pointed; their dorsal fin has 79 to 89 rays; their pectoral fins have 10 rays and are pointed and longer than the head; and, their pelvic fin is located mid-body. They have 17 or 18 long slender gill rakers on their lower arch. The and they are covered with rough scales and their lateral line is straight and gradually arches over the pectoral fins.

The Longfin Sanddab is a demersal species that is found over sandy and muddy bottoms at depths up to 250 m (820 feet). They reach a maximum length of 29 cm (11.4 inches), with females being larger than males. They consume a wide variety of crustaceans (amphipods, clams, copepods, muscles, sea cucumbers, shrimp and polychaete worms) and small fish. In turn they are preyed upon by a variety of marine mammals, larger fish, and sea birds. Reproduction is oviparous with distinct pairing. Each female produces numerous eggs on a continual basis year-round. They have life spans of up to ten years.

The Longfin Sanddab closely resembles and is easily confused with the Fantail Sole, Xystreurys liopepis, the Gulf Sanddab, Citharichthys fragilis, the Mimic Sanddab, Citharichthys gordae, the Pacific Sanddab, Citharichthys sordidus, the Small Sanddab, Citharichthys platophrys, and the Speckled Sanddab, Citharichthys stigmaeus, however, all of these Sand Flounders lack the ocelli’s spotting pattern found on the back of the Longfin Sanddab.

The Longfin Sanddab is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja.

From a conservation perspective the Longfin Sanddab has not been formally evaluated. They are considered to be a quality food fish but are not overly abundant, small in stature and retained primarily by subsistence fishermen.