Lethrinus scoparius Gilchrist & Thompson, 1908

Holleman, Wouter & Gouws, Gavin, 2022, Resurrection of Lethrinus scoparius Gilchrist & Thompson, 1908 (Perciformes: Lethrinidae), from South African waters, Zootaxa 5174 (5), pp. 551-567 : 556-557

Lethrinus scoparius Gilchrist & Thompson, 1908

Suggested common name: Natal emperor

Figs. 6–9 , Table 2

Diagnosis. Body yellowish in life, with faint blue markings on face and body, and irregular, dusky bars across body sometimes visible underwater; opercle yellow; pectoral and pelvic fins yellow to pale yellow. Dorsal and caudal fins with red margins. Out of water, some fish assume a stress pattern of irregular, brownish bars against a pale background. Preorbital length in head length 2.43–3.31, mean 2.86.

Description. Dorsal fin X, 9, 4 th or 5 th spine longest; anal fin III, 8; pectoral fins 13; pelvic fins I, 5; LL 45–48; scales from 5 th dorsal-fin ray to LL 5 or 5½; scales from LL to 1 st anal-fin spine 14½ or 15; circumpeduncular scales 9 + 13 (9 + 15 including LL scales). Exposed portion of opercle fully scaled; small patch of about 12 scales in two vertical rows immediately behind eye; supraorbital patch with 5–9 scales, and small patch of about 8 scales on upper, exposed portion of supracleithrum. Inner surface of pectoral peduncle with many small scales. Teeth: few canines in front of upper and lower jaws, more rounded at sides of jaws with smaller, rounded teeth behind.

In SL: head 2.63–3.21, body depth 2.33–2.68; in HL: eye diameter 3.30–4.49, preorbital length 2.42–3.31; eye diameter 0.50–0.89 in cheek height. All other morphometrics are listed in Table 2.

Colour under water ( Figs. 7 a-c): grayish brown with pale blue markings on body and face; darker blue oval spot at origin of lateral line; dorsal fin hyaline, anal fin pale blue anteriorly, upper- and lowermost rays of caudal fin blueish, pectoral fins hyaline. Some fish also show a ‘stress’ pattern underwater ( Figs. 7d ), or with a dark band above and a pale band below mid-body ( Fig. 7e ). Juvenile with top of head and nape yellowish ( Fig. 8 ).

Colour fresh ( Figs. 9a, b ): head above mouth yellow-gold, with blue stripe below and in front of eye, and blue spot, smaller than pupil, at origin of lateral line; dorsal half of body yellowish with pale blue marks, whitish ventrally; dorsal, caudal, anal and pectoral fins yellowish. Membranes between pelvic-fin rays with dense, small melanophores.

Colour in preservative. Pale cream to brown, with no other markings except melanophores on pectoral fins.

Maximum size recorded: 39 cm FL.

Distribution. The species is known from southern Mozambique, where its distribution overlaps with that of Lethrinus nebulosus , to Algoa Bay (34°38’ S).

Remarks. Lethrinus scoparius is the dominant species on the KwaZulu-Natal coast in South Africa, occurs in large numbers, and forms an important component of the commercial catch ( Dunlop & Mann 2013). Lethrinus nebulosus is much more tropical in distribution and is seldom seen south of iSimangaliso Wetland Park, South Africa (32° S).

In life and as fresh specimens the two species can readily be distinguished by differences in colouration. Lethrinus scoparius has less prominent blue pigmentation, noticeably along the upper edge of the pectoral fins, while photographs of live and fresh specimens show a thin blue edge to the upper and lower lobes of the caudal fin. The margins of the first and second dorsal fins and the posterior edge of the caudal fin may be tinged with red, not observed in L. nebulosus . However, the juveniles of L. scoparius and L nebulous are very similar with yellow colouration on the snout and nape and hence easily confused. In life they can also rapidly switch on and off the brown ‘stress pattern’.

The two species are practically impossible to tell apart morphometrically and meristically; the morphometrics of the two species are almost identical (Table 2), except for preorbital length in head length, a mean of 3.30 for L. nebulosus and cf. 2.86 for L. scoparius . It must also be noted that the specimens of L. nebulosus examined in this study (including one from Eilat and one from the southern Gulf of Suez) have 14½–15 scale rows between the lateral line and the origin of the anal fin, which differs from the 16–17 recorded by Carpenter & Allen (1998).

Figures

FIGURE 6. Lethrinus scoparius, Holotype, SAM 9972 (O Gon, NRF/SAIAB).

FIGURE 7–8. 7a. Lethrinus scoparius, from off Umdloti, KwaZulu-Natal, South Africa (© D King, taken in uShaka Sea World aquarium); 7b. & 7c. with ‘normal’ colour pattern (A Bernard), 7d. with ‘stress’ pattern, and 7e. with banded colour pattern, Pondoland, South Africa (BQ Mann). 8. Lethrinus scoparius juvenile, Rocky Bay, KwaZulu-Natal (© D King).

FIGURE 9. a. Lethrinus scoparius freshly caught, Aliwal Shoal, KwaZulu-Natal (CD Buxton); b. with stress pattern, Pondoland, South Africa (BQ Mann).