Choerodon jordani ( Snyder, 1908 )

Martin F., Martin F., 2017, A review of the tuskfishes, genus Choerodon (Labridae, Perciformes), with descriptions of three new species, Memoirs of Museum Victoria 76, pp. 1-111 : 79-81

Choerodon jordani ( Snyder, 1908)

Dagger Tuskfish

Choerops jordani Snyder, 1908: 98 , Naha (Okinawa, Japan).

Diagnosis. Dorsal fin rays XIII, 7 (rarely XIV, 6); anal fin rays III, 10; pectoral fin rays ii, 13, dorsalmost ray short 9.6–17.5% pectoral fin length, ventralmost rays shorter than those above, posterior edge of fin obliquely straight, dorsoposterior corner bluntly pointed, posteroventral corner angular; body shallow, 29.8–33.0% SL, head depth 22.1– 28.1% SL, caudal peduncle depth 11.7–13.1% SL; head bluntly pointed, dorsal profile of snout moderately steep, snout length 9.8–12.5% SL; predorsal scales approximately 5 or 6, reaching forward on dorsal midline to above posterior extent of eye; cheek with small partially embedded scales in about 7–10 diagonal rows, posteriormost with about 10 scales to upper extent of free preopercular edge, reaching forward almost to corner of upper lip crease above mouth, with broad naked margin posteriorly and ventrally on preopercle; 2 rows of about 8–10 small scales with only single scale in second row on subopercle adjacent preopercular edge extending forward nearly to anterior end of ventral preopercular margin; each lateral line scale with single branched laterosensory canal tube; scales above lateral line about 2½ or 3; cephalic sensory canal pores numerous behind eyes immediately in front of predorsal scales, far fewer confined to lines or short branches associated with major canals between and in front of eyes; second pair of canines in lower jaw directed dorsolaterally and curved posteriorly; dorsal and anal fins without prominent basal sheath, 1–3 progressively smaller accessory scales adjacent to fin base; posterior lobe of dorsal and anal fins not quite reaching hypural crease; caudal fin truncate, corners slightly produced in large individuals; pelvic fin reaching to or not quite to anal fin origin, just short of anus in small individuals, length 19.5–27.3% SL. (See Table 5 for additional meristic and morphometric ranges.) Grey above, white below, separated by broad yellow midlateral stripe, broad anteriorly tapered wedge-shaped stripe above lateral midline and large white oval spot below posterior end of dorsal fin and on anterior end of caudal peduncle.

Reaches moderately small maximum size, largest specimen examined 136 mm SL but reported to 170 mm TL ( Kuiter, 2010: 64).

Pigmentation in alcohol. Juveniles pale, slightly duskier above with dark blotch dorsally on side extending onto base of dorsal fin at proximal ends of first few rays and second dorsally at posterior end of caudal pecuncle, dark blotches separated by stark white oval patch; fins otherwise colourless. Adults pale with broad dark anteriorly tapering, oblique band from axilla of pectoral fin to bases of first few soft rays of dorsal fin, covering basal third of fin to posterior edge; immaculate pale blotch covering dorsal half of side and top of caudal pecuncle posterior to dark band to hypural crease defined ventrally by dusky pigment; dorsal edge of caudal fin darker.

Fresh colours. Juveniles pale grey with yellow midlateral stripe from anterior tip of mouth to middle of side followed by broad orange patch to base of tail (fig. 41A & B); small juveniles with bright white stripe above yellow and orange stripes, broken by extension of orange patch to dorsal profile of side at bases of last few dorsal fin spines; prominent white edged black spot on dorsal fin immediately above orange patch; caudal fin base with prominent white spot at corners of caudal base dorsally and ventrally; fins otherwise mostly clear. With growth, black spot developing in advance of white spot dorsally on caudal fin base and black spot on dorsal fin enveloping orange patch below ( Chen et al., 2010: 382, fig. A & 383, figs B & C; Kuiter, 2010: 64, figs D–F).

Adults grey dorsally, white ventrally with broad yellow midlateral stripe separating the two (fig. 41C & D); black wedge-shaped stripe from just above axilla of pectoral fin to caudal fin base extending as black margin on dorsal edge of caudal fin, lower edge on lateral midline and upper edge angled to base of last dorsal fin spine and continuing onto base of dorsal fin posteriorly; prominent yellow to white spot superimposed on black wedge posteriorly, appearing as saddle on caudal peduncle. Dorsal and caudal fins otherwise grey; anal and pelvic fins white; pectoral fin hyaline ( Masuda et al., 1984: pl. 193, fig. E; Allen, 1985: 2407, fig. 332; Shen, 1993: pl. 144, fig. 4; Okamura & Amaoka, 1997: 465, centre second from bottom and right second from top and middle; Chen et al., 2010: 382, fig. D; Kuiter, 2010: 64, figs A–C and G).

Terminal phase adult colouration if differing from initial phase not prominent.

Etymology. The name jordani recognises David Starr Jordan, the then President of Stanford University and accomplished ichthyologist.

Distribution. Antitropical in the western Pacific (fig. 42), confined to Japan south of Kochi ( Nakabo, 2000: 970), Taiwan and the coast of south-east Asia to Hong Kong in the north, occurring on both coasts of Australia south to the Abrolhos Islands in Western Australia and One Tree Island on the Great Barrier Reef, extending eastward to New Caledonia, Vanuatu, Tonga, Fiji ( Randall, 2005: 401; Seeto & Baldwyn, 2010: 39) and American Samoa. Lives over sand and rubble along reef edges at depths of 5–40 m ( Kuiter, 2010: 64).

Comments. Snyder (1908: 98) based his description of Choerops jordani on four specimens acquired from the Naha , Okinawa fish market, designating USNM 62235 (120 mm SL) as holotype .

The species is distinctive, resembling only the very similar C. zosterophorus , an apparent alloptric cognate distributed in intervening equatorial latitudes. The two species, along with C. frenatus , which lacks a prominent black or white marking on the side, are the only members of the subgenus with a dorsal fin count of XIII, 7 and the more conventional pectoral fin profile of other subgenera. Choerodon zosterophorus is distinguishable from C. jordani in having an obvious blunt ended oblique white band bordered by a black blotch dorsoposteriorly in place of the black wedge-shaped band on the side.

Material examined. 49 specimens examined, 23–136 mm SL; see appendix.