Choerodon venustus ( De Vis, 1884 )

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 : 38

Choerodon venustus ( De Vis, 1884)

Venus Tuskfish

Choerops venustus De Vis, 1884: 147 , Moreton Bay (Queensland). Choerodon ambiguus Ogilby, 1910b: 100 , 19 miles N 30° W from

Double Island Point (Queensland) .

Diagnosis. Dorsal fin rays XIII, 7; anal fin rays III, 10; pectoral fin rays ii, 14, dorsalmost ray of moderate length 24.9–46.8% pectoral fin length, ventralmost rays shorter than those above, posterior edge of fin obliquely straight, dorsoposterior corner bluntly pointed, posteroventral corner angular; body deep, 36.4–41.5% SL, head depth 26.1–37.2% SL, caudal peduncle depth 12.9–15.0% SL; head bluntly pointed, dorsal profile of snout moderately steep, snout length 11.9–18.6% SL; predorsal scales approximately 4–6, reaching forward on dorsal midline to not quite to above posterior edge of preopercle; cheek with small partially embedded scales in about 5 or 6 diagonal rows, posteriormost with about 10–12 scales to upper extent of free preopercular edge, reaching forward noticeably short of corner of upper lip crease above mouth, with broad naked margin posteriorly and ventrally on preopercle; row of about 8–11 small scales on subopercle adjacent preopercular edge extending forward in advance of middle of ventral preopercular margin; each lateral line scale with multiple branched laterosensory canal tube; scales above lateral line about 3½ or 4; many cephalic sensory canal pores above and behind eyes; second pair of canines in lower jaw directed anterodorsally, very little laterally; dorsal and anal fins with very low basal sheath comprising 1–3 progressively smaller accessory scales at deepest; posterior lobe of dorsal and anal fins not quite reaching hypural crease; caudal fin double emarginate, upper and lower lobes distinctly but not greatly produced, posterior margin of fin concave, smoothly curved; pelvic fin reaching to or just past anus, length 21.3– 22.9% SL. (See Table 3 for additional meristic and morphometric ranges.) Adults bluish green above, red laterally and white below, each scale on side with blue dot; juveniles with black spot between lateral line and bases of middle segmented dorsal fin rays.

Reaches moderately large maximum size, largest specimen examined 384 mm SL but reported to at least 430 mm by De Vis (1884).

Pigmentation in alcohol. Juveniles pale with dark spot larger than pupil above lateral line and below second and third soft dorsal fin rays, much smaller spot on dorsal edge of caudal peduncle midway between dorsal fin insertion and hypural crease; dorsal and caudal fins mostly faintly dusky; other fins pale. Adults pale, slightly duskier dorsally with dusky spot on each scale of caudal peduncle, becoming less evident anteriorly; head with pair of dusky marks adjacent to anteroventral margin of eye with additional marks posteroventral to eye and sometimes on snout near upper lip. Fins pale, dorsal and anal fin with row of dusky spots submarginally and second above each base; distal half of caudal fin dusky.

Fresh colours. Juveniles brown above with broad black midlateral smudges and distinct black spot in position occupied by smaller red spot below segmented dorsal fin rays of adults (fig. 16A; Kuiter, 2010: 52, fig. B).

Initial phase adults bluish green above, pale crimson midlaterally and white below; each scale on side with blue spot (fig. 16B); red blotch midlaterally posterior to pectoral fin base and smaller red blotch just above lateral line beneath segmented dorsal fin rays; eye edged with blue, with yellow patch anteriorly, forward directed mark at middle of patch; blue lines along edges of lips, upper followed by yellow line; chin and throat pale blue. Dorsal fin yellow with blue basal and marginal stripes and intermediate row of blue spots; anal fin yellow with broad blue submarginal stripe broken posteriorly and series of blue spots near base; caudal fin greenish yellow with some middle rays blue. Pectoral fin with upper rays and bases of other rays blue; base of fin yellow ( Kuiter, 2010: 52, figs. A & C).

Terminal phase individuals with vivid colours and much of side midlaterally dominated by bright pinkish red colouration (fig. 16C; Marshall, 1964: colour pl. 44, fig. 294; Kuiter, 2010: 52, fig. D).

Etymology. The name venustus is Latin for “beautiful”, no doubt a reference to the attractive colouration of this species.

Distribution. Confined to eastern Australia from the central Great Barrier Reef north of Townsville to off Newcastle, New South Wales (fig. 17). The northernmost verifiable record of distribution is the south-western end of Wardle Reef (17° 27' S, 146° 30' E) based on a photographic image (J. Johnson, personal communication). Occurs in shallow inshore weedy habitats, open substrates with rubble and attached sargassum, ranging into deeper sponge habitats ( Kuiter, 2010: 52) at depths of 20– 60 m.

Comments. Although De Vis gave the length for his Choerops venustus as “to 22 inches ” (550 mm), only a single specimen (QMB I. 4735, 234 mm SL) in the Queensland Museum collection appears to be a type for this species. This specimen no longer retains the life colours but matches the description morphologically. Ogilby’s (1910b) detailed description of Choerodon ambiguus likewise matches this species. Only one of two specimens used for the description (AMS I. 12535, 134 mm SL) is so identified in the Australian Museum collection, but at least seven others in the collection taken by the Endeavour in the same general area may be some of the 13 trawled at the same time as reported in the description. The second “co-type” is the larger of the two, measuring 181 mm TL (144 mm SL), and is likely to be AMS E.1473 with those lengths.

Taken occasionally along Australia’s Queensland coast by commercial trawlers at a marketable size, this attractive species is distinguishable from most other congeners in the area by the concave to forked posterior margin of the caudal fin, which is truncate to rounded in others, apart from C. vitta that is recognisable by its more symmetrically pointed head.

Material examined. 56 specimens, 48–384 mm SL; see appendix.