Choerodon schoenleinii (Valenciennes, 1839)

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 : 32-37

Choerodon schoenleinii (Valenciennes, 1839)

Blackspot Tuskfish

Cossyphus Schoenleinii Valenciennes , in Cuvier & Valenciennes,

1839: 143, Celebes ( Indonesia). Cossyphus cyanostolus Richardson, 1846: 256 , Canton ( China). Cossyphus ommopterus Richardson, 1846: 257 , Canton ( China). Choerops unimaculatus Cartier, 1874: 102, Cavite ( Philippines). Torresia australis Castelnau, 1875: 36 , Cape York (Queensland). Chaerops notatus Alleyne & Macleay, 1877: 344 , pl. XVI, fig. 1,

Cape Grenville (Queensland). Torresia lineata De Vis, 1885: 881 , Cardwell (Queensland). Choerops nyctemblema Jordan & Evermann, 1902: 353, fig. 21,

Formosa. Choerodon rubidus Scott, 1959: 89 , fig. 7, Shark Bay (Western

Australia).

Diagnosis. Dorsal fin rays XIII, 7; anal fin rays III, 10; pectoral fin rays ii, 16, rarely 17, dorsalmost ray dorsalmost ray of moderate length 41.5–53.9% pectoral fin length, ventralmost rays shorter than those above, posterior edge of fin obliquely straight, dorsoposterior corner bluntly pointed, posteroventral corner angular; body deep, 32.8–43.4% SL, head depth 23.7– 38.5% SL, caudal peduncle depth 11.8–16.4% SL; head bluntly pointed, dorsal profile of snout moderately steep, snout length 9.0–16.9% SL; predorsal scales approximately 5–7, reaching forward on dorsal midline not quite to or just in advance of posterior edge of preopercle; cheek with moderately large nonimbricate scales in about 5–9 diagonal rows, posteriormost with about 13 scales to upper extent of free preopercular edge, reaching forward to or nearly to corner of upper lip crease above mouth, with moderately broad naked margin posteriorly and ventrally on preopercle; row of 2–5 small scales on subopercle adjacent preopercular edge at or just above preopercular corner; each lateral line scale with multiple branched laterosensory canal tube in large individuals; scales above lateral line about 3 or 3½; cephalic sensory canal pores numerous above and behind eyes less so in front of and below eyes; second pair of canines in lower jaw directed anterodorsally, very little laterally; dorsal and anal fins with low basal sheath comprising 1–3 progressively smaller accessory scales at deepest; posterior lobe of dorsal and anal fins not quite reaching hypural crease in juveniles, reaching hypural crease in adults; caudal fin truncate to slightly rounded, upper and lower corners only barely produced at most in large individuals; pelvic fin reaching to base of second anal fin spine in large individuals, length 19.1–27.3% SL. (See Table 3 for additional meristic and morphometric ranges.) Adults bluish green above with yellow sides and vertical blue line of each body scale; black spot on body at base of last dorsal fin spot and white patch often between lateral line and middle segmented dorsal fin rays; head with diagonal blue lines angled from and below eye.

Reaches large maximum size, largest specimen examined 530 mm SL. Reported in the literature to reach 1 m ( Kuiter, 2010: 59).

Pigmentation in alcohol. Juveniles pale dusky above, pale below with narrow dusky stripes following horizontal rows of scales especially posteriorly, prominent dark spot on scaly sheath of dorsal fin below last dorsal fin spine; head dusky above and pale ventrally, with 2 dark dusky stripes directed posteriorly from lower half of eye and another 2 from lower half of eye anteroventrally towards upper jaw; fins pale, dorsal and anal with dusky sub-basal stripe, anal with sub-distal stripe; caudal fin pale dusky basally near middle of fin. Initial phase adults pale with duskier dorsum; dark spot on scaly dorsal fin sheath prominent. Terminal phase adults rather dark, scales on side and chest with broad dark margins; lateral line and pectoral fin base dark; caudal peduncle with about 6 horizontal rows of dark spots; dark spot on scaly base of dorsal fin small or absent; fins dusky.

Fresh colours. Juveniles (fig. 13A) tan to pale brown with 8–10 fine white mostly vertical bars dorsally across back, those posteriorly across underside of caudal peduncle as well; head with narrow brown bands directed dosally, anteroventrally and ventrally from eye; white spot at base of pectoral fin, and dorsally and ventrally on caudal fin base; fins transparent with broad vertical tan patches covering anterior and middle of dorsal fin, pelvic fin and anterior end of anal fin; small dark brown to black spot at base of last dorsal fin spine.

Initial phase adults olive, washed with blue above, often yellow below with vertical blue line on each body scale, those posteriorly merging to form horizontal blue lines (fig. 13B); pairs of blue lines directed anteroventrally and posteriorly from orbit; underside of head orange to yellow, lower jaw blue; teeth blue; blue line at base of pectoral fin; distinctive black spot on body at base of last dorsal fin spine; white blotch often on body below segmented dorsal fin rays in smaller individuals. Dorsal and anal fins with narrow horizontal blue lines; caudal fin with narrow blue bands; pelvic fin with blue leading endge ( Masuda et al., 1984: pl. 194, fig. A; Shen, 1993: pl. 144, fig. 6; Okamura & Amaoka, 1997: 465, right second from bottom; Chen et al., 2010: 383, fig. F; Kuiter, 2010: 59, figs B–E; Allen & Erdamann, 2012: 648, top of page; White et al., 2013: 267, fig. 89.17 female).

Terminal phase adults dark bluish green with little if any indication of white spot posteroventral to black spot (fig. 13C); lower jaw and caudal fin rays blue ( Masuda et al., 1984: pl. 194, fig. B; Sainsbury & Kailola, 1984: 259, top; Okamura & Amaoka, 1997: 465, centre bottom; Kuiter, 2010: 59, figs A & F; Allen & Erdamann, 2012: 648, centre of page).

Etymology. The origin of the name schoenleinii is unclear, although Valenciennes speculated that Agassiz intended it to recognise Johann Lukas Schoenlein, an important medical scientist of the Biedermeier Zeit, following the Napleonic wars, 1815–1858 (Pietsch, Eschmeyer and Fairclough, personal communication).

Distribution. Occurs along the western edge of the Pacific from Okinawa in southern Japan ( Nakabo, 2000: 971) and China to both the eastern and western coasts of northern Australia, at least to Shark Bay in Western Australia and Sydney Harbour in New South Wales (fig. 15); not recorded east of the Philippines, Papua New Guinea and eastern Australia. Found on silty or sand to rubble bottoms often with algal cover in lagoons and near coastal reefs at depths of 0.3– 46 m.

Comments. Valenciennes (in Cuvier & Valenciennes, 1839: 143) based his description of Cossyphus Schoenleinii on a colour figure of a specimen collected in Celebes (Sulawesi, Indonesia) and conveyed to him by Agassiz. Meristic discrepancies involving soft anal fin and pectoral fin ray counts between his description and the species described here are attributed to the inaccuracy of the figure .

Both Cossyphus cyanostolus and Cossyphus ommopterus were described by Richardson (1846: 256, BMNH 1968.3.11.15, 280 mm SL, and 257, BMNH 1968.3.11.16, 124 mm SL, respectively) from dried specimens collected in Canton ( China) with accompanying detailed colour drawings (fig. 14A and B, respectively). They are clearly synonyms of C. schoenleinii . Cartier’s (1874: 102) description of Choerops unimaculatus is based on juveniles as corroborated by the stated lengths of his type series, 3.9–6.7 cm. Although the types appear to have been lost ( Eschmeyer, 2015), the colour pattern is that of C. schoenleinii . The description of Castelnau’s (1875: 36) Torresia australis is similarly brief and could apply to more than one species, but the colour account most closely matches that of juvenile C. schoenleinii . The disposition of the type is unknown. Morphological details in Alleyne and Macleay’s (1877) description of Chaerops notatus are inconclusive as to the identity of this species, but the colouration and type (AMS I.16360-001, 216 mm SL) specimen identify it as a synonym of C. schoenleinii . De Vis’s (1885: 881) description of Torresia lineata is also very brief morphologically, but the colour description is clearly that of a juvenile C. schoenleinii . The type (QMB I. 11/82, ~ 80 mm SL) is in poor condition, but is identifiable as C. schoenleinii in having 16 branched pectoral fin rays. This is the only species in the Cardwell, Queensland region regularly with that number of pectoral fin rays.

Choerops nyctemblema Jordan & Evermann (1902: 353, fig. 21) was based on a single 18 inch (72 cm) specimen collected in Formosa (Taiwan) that no longer appears to be extant. The description is brief, but of the seven species of Choerodon known to occur in Taiwan, it most closely resembles C. schoenleninii . The account is consistent with a large example, none of the other six species attaining a length greater than 430 mm SL. Although the authors did not provide a pectoral fin count, the published figure has ii, 16 rays, supporting the identification, with the other six species having 14 (rarely 15) or fewer branched rays. Choerodon rubidus described by Scott (1959: 89, a second fig. 7 on that page, labelled Stethojulis rubromacula sp. nov.) is based on a 167 mm SL (210 mm TL, SAM F2985) specimen from Point Samson, Western Australia, identifiable as C. schoenleinii . Scott gave Shark Bay as the type locality but this appears to be an error, as is the caption for the figure of the species, which is repeated verbatim from the preceding figure. The description also contains a number of contradictions that are likely to have been innaccuracies in data capture, such as the anal fin count of “iii, 11” rather than III, 10, and the pectoral fin count of “17” rather than ii, 16. The type has the latter values typical of C. schoenleinii .

As discussed below, Parenti and Randall (2000: 10) synonymised Choerodon quadrifasciatus Yu, 1968 with Choerodon schoenleinii but that name is considered here to be a synonym of C. azurio .

Choerodon schoenleinii is a common species that reaches a relatively large size, explaining its frequency in fish markets throughout the western extreme of the tropical Pacific and consequently its representation in museum collections. The relatively small but prominent black spot on the scaly sheath at the base of the dorsal fin sets it apart from adults of other species, with the possible exception of C. monostigma , which has a larger black spot setting higher on the fin and 14 rather than 16 or 17 segmented pectoral fin rays.

Ebisawa et al. (1995) studied reproduction and sex change in this species.

Material examined. 113 specimens, 21–530 mm SL; see appendix.