Stolephorus concursus, Hata & Motomura, 2021

Hata, Harutaka & Motomura, Hiroyuki, 2021, Two new species of Stolephorus (Teleostei: Clupeiformes: Engraulidae) from the western Pacific, Raffles Bulletin of Zoology 69, pp. 109-117 : 114-115

Stolephorus concursus , new species

[New English name: Concourse Anchovy] ( Fig. 4 ; Tables 1, 2)

Holotype. USNM 330901 , 72.8 mm SL, Nadi Bay , Viti Levu Island, Fiji, 4 July 1973.

Paratypes. 23 specimens, 68.7–84.7 mm SL. BPBM 38338 , 2 specimens, 82.2–84.7 mm SL, Pangaimotu, Vava’u, Tonga; URM-P. 33477, 84.7 mm SL, Vava’u Bay , Vava’u Island, Vava’u Islands, Tonga; USNM 451515 , 3 specimens, 68.9– 73.4 mm SL, KAUM –I. 146839, 75.8 mm SL, KAUM – I. 146840, 79.4 mm SL, NSMT-P 139185 , 75.1 mm SL, NSMT-P 139186 , 73.0 mm SL, collected with holotype; USNM 330906 , 13 specimens, 69.7–74.6 mm SL, Fiji .

Diagnosis. A species of Stolephorus with the following combination of characters: long maxilla, 22.5–25.2% SL (mean 23.7%), its posterior tip slightly short of or extending beyond posterior margin of opercle; no predorsal scute; pelvic scute without spine; gill rakers 16–18 (modally 17) in upper series on first gill arch, 21–23 (23) in lower series, 38–41 (39) in total; gill rakers 11–13 (12) in upper series on second gill arch, 19–22 (20) in lower series, 30–34 (32) in total; gill rakers 9 or 10 (9) in upper series on third gill arch, 10–12 (12) in lower series, 19–22 (21) in total; gill rakers 7–9 (8) in upper series on fourth gill arch, 9–11 (10) in lower, 16–19 (18) in total; gill rakers 4–6 (5) on hind face of third gill arch; prepelvic scutes 3–6 (6); transverse scales 8 or 9 (8); pseudobranchial filaments 19–25 (22); paired dark patches on parietal and occipital regions without a following pair of dark lines; numerous black spots on suborbital area, snout, and lower-jaw tip; depressed pelvic fin extending posteriorly beyond vertical through dorsal-fin origin; snout long, 4.8–5.4% SL (mean 5.0%); pectoral fin rather long, 16.5–18.1% SL (17.0%); pelvic fin long, 9.5–10.6% SL (10.1%); head large, 26.4–28.5% SL (27.4%); lower jaw long, 19.1–20.7% SL (19.9%).

Description. Data for holotype presented first, followed by paratype data in parentheses (if different). Counts and measurements, expressed as percentages of SL or HL, given in Tables 1 and 2.

Body laterally compressed, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body gently elevated from snout tip to dorsal-fin origin, thereafter gradually 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 nearly straight and parallel to body axis and ventral profile of body from anal-fin origin to caudal fin base slowly rising. Abdomen rounded, covered with six (three to six) spine-like scutes. Postpelvic and predorsal 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 backward beyond posterior margin of eye. Maxilla long, its posterior tip pointed, just short of or reaching posterior border of opercle. Lower jaw slender. Single row of conical teeth on each jaw and palatines. Small conical teeth patch on pterygoids. Several small conical teeth on vomer. 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 margins of preopercle and opercle, smooth. Subopercle with rounded posterior margin. Posterior margin of preopercle indented, convex (rounded, concave in one paratype). Gill membrane without serrations. Interorbital space flat, width less than eye diameter. Pseudobranchial filaments present, longest filament shorter than eye diameter. Gill rakers long, slender, rough, visible from side of head when mouth opened. Isthmus muscle long, reaching anteriorly to posterior margin of gill membranes. Urohyal hidden by isthmus muscle (visible only following dissection). Gill membrane on each side joined distally, most of isthmus muscle exposed (not covered by gill membrane). Scales cycloid, thin, deciduous, except for prepelvic scutes. Numerous vertical grooves on body scales. Head scales and lateral line 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 midpoint of body. Dorsal and anal fins with three anteriormost rays unbranched and closely spaced, first ray of both fins minute. Anal-fin origin just below base of eleventh (ninth to twelfth) dorsal-fin ray. Posterior tip of depressed anal fin not reaching caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below midline of body. Posterior tip of pectoral fin not reaching vertical through pelvic-fin insertion; pelvic fin shorter than pectoral fin; pelvic-fin insertion anterior to vertical through dorsal-fin base. Posterior tip of depressed pelvic fin reaching to vertical through third (first to sixth) dorsal-fin ray origin. Colour of preserved specimens. Body uniformly pale ivory with whitish longitudinal band, slightly less than pupil diameter, from just posterior to upper opercular margin to caudal-fin base. Pairs of dark patches on parietal and occipital regions. No dark lines on dorsum. Numerous black spots on snout, lower-jaw tip, and suborbital area. Melanophores scattered on posterior margin of dorsal scale pockets. All fins whitish, semi-transparent. Melanophores scattered along fin rays of dorsal and caudal fins. Posterior margin of caudal fin dark. Live and fresh colouration unknown.

Distribution. Currently known only from Tonga and Fiji.

Etymology. The specific name concursus is derived from Latin meaning “crowd”, in reference to the schooling habit of the species.

Comparisons. Included in the genus Stolephorus sensu Whitehead et al. (1988) and Wongratana et al. (1999) (see “Comparisons” under S. celsior ), the new species is easily distinguishable from all other congeners—except for S. babarani , S. bataviensis , S. baweanensis , and S. celsior , new species —by the long upper jaw, its posterior tip beyond the preopercle posterior margin (slightly short of or extending beyond the opercle posterior margin), and numerous dusky spots on the suborbital area, snout, and lower-jaw tip ( Whitehead et al., 1988; Wongratana et al., 1999; Kimura et al., 2009; Hata & Motomura, 2018a –d; Hata et al., 2019, 2020a, b, 2021; Gangan et al., 2020; this study). However, the former is easily distinguished from S. babarani , S. baweanensis , and S. celsior by the posterior tip of the depressed pelvic fin extending beyond vertical through the dorsal-fin origin (vs. not reaching to below the dorsal fin origin in the other three species), a longer snout (4.8–5.4% SL in S. concursus vs. <4.6% SL; Table 2; Fig. 3H ) and mandible (19.1–20.7% SL vs. <19.0%; Table 2; Fig. 3C ), and higher vertebral number [total vertebrae 40 or 41 (modally 40) vs. 39 or 40 (39) in S. baweanensis , 39 or fewer in S. babarani and S. celsior ; Tables 1, 3]. Stolephorus concursus further differs from S. babarani and S. baweanensis in having a longer head (26.4–28.5% SL vs. 23.9–25.5% in S. babarani ; 23.9–27.1% in S. baweanensis ; Table 2; Fig. 3F ), pectoral fin (16.5–18.1% SL vs. 15.0–16.3% in S. babarani ; 14.0–16.8% SL in S. baweanensis ; Table 2; Fig. 3B ), and pelvic fin (9.5–10.6% SL vs. 8.1–9.4% in S. babarani ; 6.5–9.4% in S. baweanensis ; Table 2; Fig. 3D ), and from S. babarani in maxilla length (22.5–25.2% SL in S. concursus vs. 20.8–22.3% in S. babarani ; Table 2; Fig. 3I ). Stolephorus concursus is distinguished from S. celsior by higher longitudinal series scale row numbers (35–37 in S. concursus vs. 34–35 in S. celsior ; Table 1).

Stolephorus concursus differs from S. bataviensis in having higher gill raker numbers on the first [16–18 (modally 17) + 21–23 (23) = 38–41 (39) vs. 14–17 (15) + 19–22 (20) = 33–38 (35) in S. bataviensis ; Fig. 2A ] and second gill arches [11–13 (modally 12) + 19–22 (20) = 30–34 (32) vs. 9–12 (11) + 17–20 (18) = 27–32 (29); Fig. 2B ], and a longer snout [4.8–5.4% SL (mean 5.0%) vs. 3.7–4.7% (4.3%); Fig. 3H ] and pectoral fin [16.5–18.1% SL (17.0%) vs. 14.7–16.4% (15.5%); Fig. 3B ].

Figures

Fig. 4. (A) Body and (B) head of holotype of Stolephorus concursus, new species, USNM 330901, 72.8 mm SL, Nadi Bay, Viti Levu Island, Fiji.

Fig. 3. Morphometrics and meristic of Stolephorus celsior, new species (triangles), S. concursus, new species (circles), S. babarani (inverted triangles), S. bataviensis (squares), and S. baweanensis (diamonds) (all vs. standard length; SL). A, ratio of caudal-peduncle depth to SL; B, pectoral-fin length to SL; C, mandibular length to SL; D, pelvic-fin length to SL; E, distance from dorsal-fin origin to pelvic-fin insertion to SL; F, head length to SL; G, orbit diameter to SL; H, snout length to SL; I, maxilla length to SL.

Fig. 2. Relationships of total gill-raker numbers (TGR) on (A) first gill arch (1GA), (B) second gill arch (2GA), (C) third gill arch, and (D) fourth gill arch relative to standard length in Stolephorus celsior, new species (triangles), S. concursus, new species (circles), S. babarani (inverted triangles), S. bataviensis (squares), and S. baweanensis (diamonds).