Lemon Ghost Flathead, Hoplichthys citrinus Gilbert 1905

Benthic on soft-bottom habitats of the outer continental shelves and upper continental slopes (c. 100-435m) of the tropical west-central Pacific (recorded from Hawaiian Islands, Timor Sea, northern Australia and seamounts of the south-east Pacific). Australian range is from off Bonaparte Archipelago (~11^o49'S) south to off North West Cape (~21^o49'S), Western Australia and off Yeppoon (Queensland, ~23^o05'S) southwards to off Eden (New South Wales, ~37^o11'S). Possibly more widespread off northern Queensland (~17^oS), Norfolk Ridge (~30^oS, 168^oE) and central Western Australia (~25^oS), but these records require confirmation.

Meristic features: Dorsal fin V-VI, 15-16; Anal fin I, 16 (17 total); Pectoral fin 12-14 + 3-4; Pelvic fin I, 5; Lateral line (scutes/plates) 27-28; Gill rakers 12-14 including rudiments; Branchiostegal rays 7; Vertebrae 26.

Body depressed, shallow (~5-8% SL), elongate, moderately narrow, tapering to very narrow caudal peduncle. Head moderately large (~30-36% SL), very broad and depressed, snout wide and spatulate, lateral profile of head formed by a sharp dentigerous ridge, divided into 4 well-marked lobes: a preorbital lobe, a short lobe below front of eye, a greatly expanded rounded lobe below cheeks, and a fourth lobe constituting lower margin of opercle and ending in the very long curved preopercular spine; eyes moderately large (~22-28 % HL); interorbital space very narrow (~9-15% eye length; greater in very small specimens), concave, the margins minutely denticulate, minutely toothed areas and ridges on snout, cheeks, opercular bones and occiput, a short series of spinelets on interopercle, behind angle of mouth, and others below preorbital region, opercle marked by 5-8 rough striae diverging from the upper anterior angle, the strongest ending in the long opercular spine, a short, strong humeral spine present, mouth large (~30-34 % HL), horizontal, lower jaw shorter than upper; several rows of minute villiform teeth in jaws, in two patches on vomer and in a few rows on palatines.

Body naked with the exception of a series of lateral plates, at the angle of each is a strong, posteriorly directed spine (a much smaller and more slender spine is below each plate), plates placed obliquely antero-posteriorly, the anterior upper portion nearly horizontal, its surface roughened by 2-5 minutely denticulated ridges, the lower posterior part vertical and smooth. Sexually dimorphic; both dorsal fins greatly elevated in males, low in females. In males, first dorsal spine produced and filamentous, sometimes extending well beyond origin of soft dorsal, the upper margin of the fin deeply concave, some or all of the first to fourth soft dorsal rays are produced into long filaments. Free pectoral rays much shorter than longest connected rays. Caudal fin truncate or slightly concave, more pronounced in males where the lower caudal rays are a little longer than the upper.

In life: very bright lemon yellow or olive yellow on all upper parts, including fins; white or silvery ventrally. Faint traces of four dark bars across dorsum, more evident in smaller specimens. Yellow spots on sides, first dorsal and pectoral with black areas. In preserved specimens, dorsal surface creamy yellow, sides pale pink-yellow, first dorsal pale with black tip, second dorsal pale, other fins pale, except caudal fin with blackish tip. Eyes bluish.

Crabs and fishes have been found in the stomachs of this species.

Usually taken in trawls, although not commercially harvested.

None.

Hoplichthys citrinus Gilbert, 1905, Bull. U. S. Fish Comm. 23(2) [for 1903]: 640, Fig. 249, Pailolo Channel, Hawaiian Islands, U.S.A., Albatross station 3859, depth 138 fathoms.

CSIRO Marine & Atmospheric Research