Stolephorus eldorado, Hata & Lavoué & Motomura, 2022

Hata, Harutaka, Lavoue, Sebastien & Motomura, Hiroyuki, 2022, Description of three new species previously identified as Stolephorus bengalensis (Dutt & Babu Rao, 1959) or Stolephorus insularis Hardenberg, 1933 and a re-description of S. bengalensis (Chordata, Osteichthyes, Clupeiformes, Engraulidae), ZooKeys 1121, pp. 145-173 : 145

Stolephorus eldorado sp. nov.

[New English name: El Dorado Anchovy] Figs 1A, B, D, E, F , 11

Stolephorus insularis (not of Delsman): Whitehead et al. 1988 (in part): 413 unnumbered fig. (Taiwan to Java Sea); Young et al. 1999: 222, fig. 7 (western coast of Taiwan); Wongratana et al. 1999 (in part): 1736, unnumbered fig. (Taiwan to Java Sea); Hata 2018: 41, unnumbered figs (Ha Long Bay, northern Vietnam).

Stolephorus tri (not of Bleeker): Zhang 2001: 129, fig. II-59 (Beihai City, Guangxi Province, China).

Stolephorus bengalensis (not of Dutt and Babu Rao): Hata et al. 2019 (in part): 24, fig. 12a, b (Taiwan; Hainan Island, China; Ha Long Bay, Vietnam; Gulf of Thailand; Songkhla, Thailand; Kuala Terengganu, Terengganu, Malaysia); Hata 2019: 206, unnumbered figs (Ke-tzu-liao, Ziguan District, Kaohsiung, Taiwan); Hata et al. 2022: (in part) 34 (Wenzhou City, Zheijiang Province, China).

Holotype.

KAUM-I. 94517, 44.4 mm SL, Ha Long Bay, Ha Long City, Quang Ninh District, Vietnam (purchased at fish market in Ha Long City), 24 Oct 2016; coll. by H. Hata and M. Matsunuma.

Paratypes.

57 specimens, 37.5-58.8 mm SL. Taiwan: ASIZP 73957, 51.8 mm SL, Fangyan, Changhua (23°57'42.8"N, 120°17'39.8"E); KAUM-I. 110282, 49.5 mm SL, KAUM-I. 113142, 54.0 mm SL, KAUM-I. 113143, 45.5 mm SL, KAUM-I. 113144, 44.3 mm SL, KAUM-I. 113145, 46.3 mm SL, KAUM-I. 113146, 37.5 mm SL, KAUM-I. 113147, 47.3 mm SL, KAUM-I. 113148, 55.3 mm SL, KAUM-I. 113149, 49.4 mm SL, KAUM-I. 113150, 45.9 mm SL, KAUM-I. 113151, 47.3 mm SL, off Ke-tzu-liao, Ziguan District, Kaohsiung. China: BMNH 1965.4.1.981-983, 3 specimens, 58.1-58.8 mm SL, Stanley, Hong Kong. Vietnam: FRLM 49725, 46.9 mm SL, KAUM-I. 67322, 46.7 mm SL, KAUM-I. 67405, 45.6 mm SL, KAUM-I. 94509, 41.4 mm SL, KAUM-I. 94518, 43.7 mm SL, KAUM-I. 94519, 38.8 mm SL, KAUM-I. 94520, 41.7 mm SL, KAUM-I. 94521, 43.4 mm SL, Ha Long Bay, Ha Long, Quang Ninh Province. Thailand: CAS 46931, 8 specimens, 44.4-46.7 mm SL, between Bangsaen and Chol Buri, Chol Buri, Gulf of Thailand; CAS 230414, 4 specimens, 39.9-45.8 mm SL, Lem Nam Point, south tip of Lem Nam Peninsula, Gulf of Thailand (12°02'55"N, 102°35'35"E), approx. 0.6 m depth; KAUM-I. 23190, 48.2 mm SL, Gulf of Thailand (obtained at fish market in Mahachai, Samut Prakan Province), trawl; NSMT-P 142790, 47.9 mm SL, Ko Maeo Island, off Songkhla; URM-P 12398, 3 specimens, 43.0-45.5 mm SL, Song Khula; URM-P 13635, 11 specimens, 46.2-49.5 mm SL, Ang Sila. Indonesia: BMNH 1965.10.20.42-47, 6 specimens, 40.6-43.5 mm SL, 20 miles (approx. 32 km) east of Tegal, Java.

Diagnosis.

A species of Stolephorus with the following combination of characters: 1UGR 16-21 (modally 18), 1LGR 23-28 (25), 1TGR 40-47 (42); 2UGR 10-14 (13), 2LGR 20-24 (23), 2TGR 33-38 (rarely 30) (modally 36); 3UGR 8-12 (modally 10), 3LGR 12-14 (13), 3TGR 20-26 (23); 4UGR 7-10 (8), 4LGR 9-12 (11), 4TGR 16-22 (18); prepelvic scutes 5-7 (6); total vertebrae 38-40 (39); long maxilla, posterior tip just reaching or slightly short of posterior margin of opercle; predorsal scutes present; pelvic scute without spine; body scales deciduous; posterior border of pre-opercle concave, indented; paired dark patch on parietal area with little following pigmentation; distinct double pigment lines along dorsum posterior to dorsal fin; black spots below eye and on lower-jaw tip absent; anal-fin base long, 19.0-22.3% (20.4%) of SL; orbit rather long, 8.2-9.9% (8.9%) of SL; third dorsal-fin ray short, 15.9-18.6% (17.4%) of SL; pelvic fin rather long, 9.1-11.0% (10.0%) of SL, its posterior tip usually not reaching to vertical through dorsal-fin origin when depressed in individuals> 50 mm SL; distance between posterior ends of supramaxilla and maxilla 5.0-6.3% (5.6%) of SL.

Description.

Data for holotype presented first, followed by data for paratypes in parentheses (if different). Counts and measurements, expressed as percentages of SL or HL, given in Tables 2 and 3 . Body laterally compressed, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body slightly convex from snout tip to dorsal-fin origin, gently lowering to uppermost point of caudal-fin base. Ventral profile of head and body slightly convex from lower jaw tip to pelvic-fin insertion, thereafter, slowly rising to lowermost point of caudal-fin base. Single spine-like scute just anterior to dorsal-fin origin. Abdomen somewhat rounded, covered with six (five to seven) spine-like prepelvic scutes. Pelvic scute without spine. Postpelvic scutes absent. Anus just anterior to anal-fin origin. Snout tip rounded; snout length less than eye diameter. Mouth large, inferior, ventral to body axis, extending backwards beyond posterior margin of eye. Maxilla long, its posterior tip pointed, just reaching (or slightly short of) opercle posterior margin. Lower jaw slender. Single row of conical teeth on both jaws and palatine. Patch of fine conical teeth on pterygoid. Several distinct conical teeth on vomer. Several rows of conical teeth on upper edges of basihyal and basibranchial. Eye large, round, covered with adipose eyelid, positioned laterally on head dorsal to horizontal through pectoral-fin insertion, visible in dorsal view. Pupil round. Orbit elliptical. Nostrils close to each other, anterior to orbit. Posterior margin of pre-opercle concave, indented. Subopercle and opercle with smoothly rounded posterior margins. Gill membrane without serrations. Interorbital space flat, width less than eye diameter. Pseudobranchial filaments present, length of longest filament less than eye diameter. Gill rakers long, slender, rough, visible from side of head when mouth opened. Single row of asperities on anterior surface of gill rakers. Isthmus muscle long, reaching anteriorly to posterior margin of gill membranes. Urohyal hidden by isthmus muscle, not visible without dissection. Gill membrane on each side joined distally, most of isthmus muscle exposed, not covered by gill membrane. Body scales deciduous, completely lacking on all specimens, except for prepelvic scutes. Head scales absent. Fins scaleless, except for broad triangular sheath of scales on caudal fin. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray, slightly posterior to middle of body. Dorsal and anal fins with three anteriormost rays unbranched. First dorsal- and anal-fin rays minute. Anteriormost three rays of both dorsal and anal fins closely spaced. Anal-fin origin just below base of ninth (eighth to tenth) dorsal-fin ray. Posterior tip of depressed anal fin not reaching caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below body axis. Posterior tip of pectoral fin not reaching to pelvic fin insertion. Dorsal, ventral and posterior margins of pectoral fin nearly linear. Pelvic fin shorter than pectoral fin, insertion anterior to vertical through dorsal-fin origin. Posterior tip of depressed pelvic fin not reaching to vertical through dorsal-fin origin (reaching to vertical through first to fourth dorsal-fin ray origin in some paratypes smaller than 50 mm SL). Caudal fin forked, posterior tips pointed.

Colour of fresh specimens.

(based on colour photographs of KAUM-I. 67322, 46.7 mm SL, KAUM-I. 67405, 45.6 mm SL, KAUM-I. 94517, 44.4 mm SL, KAUM-I. 94521, 43.4 mm SL and KAUM-I. 110282, 49.5 mm SL). Body yellowish milky-white, a silver longitudinal band, of width slightly less than pupil diameter, extending from just above posterior tip of pectoral fin to caudal-fin base. Caudal fin yellow with black posterior margin. Melanophores scattered along caudal-fin rays, ventral surface of caudal peduncle and bases of dorsal and anal fins. Fin rays of dorsal and anal fins yellow. A few melanophores scattered on snout and fin rays of anterior part of dorsal fin. Fin rays and fin membrane of pectoral and pelvic fins transparent whitish, lacking melanophores. A pair of dark patches on parietal region, with little pigmentation on occipital area. Distinct double pigment lines on dorsum from end of dorsal-fin base to caudal-fin base. Body wholly yellowish when freshly caught (Fig. 11E ), quickly becoming white after death (Figs 11F-H ).

Colour of preserved specimens.

Body uniformly pale white. A pair of distinct dark patches on parietal region, with little pigmentation on occipital area. Melanophores scattered on posterior margins of scale pockets on dorsum. Double pigmented lines dorsally posterior to dorsal fin. A few melanophores scattered anteriorly on snout. No black spots below eye and on lower-jaw tip. Melanophores scattered along bases of dorsal and anal fins. All fins transparent, with melanophores scattered along fin rays of caudal fin and anterior parts of dorsal and anal fins.

Distribution.

Stolephorus eldorado sp. nov. is distributed in the western Pacific from Taiwan to Java, Indonesia (Fig. 4 ). The species is abundantly caught by trawl and marketed fresh in northern Vietnam. It is a set net bycatch in south-western Taiwan.

Etymology.

The specific name " eldorado ", referring to the mythical city of gold, reflects the bright yellow colouration of the new species.

Morphological comparisons.

Stolephorus eldorado sp. nov. has been previously identified as S. insularis or S. bengalensis (together with S. bengalensis , S. diabolus and S. eclipsis as recognised here) (e.g. Whitehead et al. 1988; Wongratana et al. 1999; Hata et al. 2019). However, S. eldorado is distinguished from S. diabolus and S. eclipsis by having an intermediate number of gill rakers on each gill arch (Table 2 ; Fig. 7 ). More detailed comparisons of S. eldorado with the latter two species are given in “Comparisons” under each species.

Although S. eldorado sp. nov. closely resembles S. bengalensis in having very similar numbers of gill rakers on each gill arch, the former differs from the latter in having a greater orbit diameter [maximum orbit diameter 8.2-9.9% (mean 8.9%) of SL vs. 7.3-8.6% (8.1%) in S. bengalensis (Fig. 8A )], shorter third dorsal-fin ray [15.9-18.6% (mean 17.4%) of SL vs. 18.5-19.9% (19.0%)] (Fig. 8B ) and fewer total vertebrae [38-40 (modally 39) vs. 40 or 41 (40)] (Table 4 ).

Figures

Figure 1. Diagnostic characters of species previously identified as Stolephorus bengalensis A lateral view of whole body B dorsal-fin origin (triangle indicates predorsal scute, located just anterior to dorsal-fin origin) C dorsal view of dorsum behind dorsal fin (triangle indicates paired dark lines) D lateral surface of head (triangle indicates posterior tip of maxilla, posteriorly well beyond posterior margin of pre-opercle) E pre-opercle with concave posterior margin (supramaxilla removed) and F ventral view of pelvic fin (triangle indicates pelvic scute, lacking spine) (A KAUM-I. 94521, paratype of S. eldorado sp. nov. in fresh condition, 43.4 mm SL, Ha Long Bay, northern Vietnam B, E, F KAUM-I. 113148, paratype of S. eldorado sp. nov., 55.3 mm SL, Ke-tzu-liao, south-western Taiwan C ZUMT 62056, paratype of S. diabolus sp. nov., 38.4 mm SL, Singapore D KAUM-I. 94509, paratype of S. eldorado sp. nov., 41.4 mm SL, Ha Long Bay, northern Vietnam) (B, D, E and F alizarin stain).

Figure 4. Map of the northern part of the Indo-West Pacific region showing distributional records of Stolephorus bengalensis (red circles), S. diabolus (yellow squares) sp. nov., S. eclipsis (green diamond) sp. nov. and S. eldorado (blue triangles) sp. nov., based on specimens examined in this study. Land masses outlined with black lines.

Figure 7. Relationships of total gill raker numbers (TGR) on A first gill arch (1 GA) B second gill arch (2 GA) C third gill arch (3 GA) and D fourth gill arch (4 GA) to standard length in Stolephorus bengalensis (red circles), S. diabolus sp. nov. (yellow squares), S. eclipsis sp. nov. (green diamonds) and S. eldorado sp. nov. (blue triangles).

Figure 8. Relationships of A orbit diameter (as % of standard length; SL) B third dorsal-fin ray length (as % of SL) C anal-fin base length (as % of SL) D pelvic-fin length (as % of SL) and E distance between posterior ends of supramaxilla and maxilla (SMX-MX) in Stolephorus bengalensis (red circles), S. diabolus sp. nov. (yellow squares), S. eclipsis sp. nov. (green diamonds) and S. eldorado sp. nov. (blue triangles).

Figure 11. Holotype of S. eldorado sp. nov. (KAUM-I. 94517, 44.4 mm SL, Ha Long Bay, northern Vietnam) A lateral view (fresh) B lateral C dorsal, and D ventral views (preserved); paratypes of S. eldorado sp. nov. (KAUM-I. 67322, 46.7 mm SL, Ha Long Bay, northern Vietnam) E lateral view (fresh), (KAUM-I. 110282, 49.5 mm SL, Ke-tzu-liao, southwestern Taiwan) F lateral G dorsal, and H ventral views (fresh). Scale bars indicate 2 mm.