Hata & Motomura: A new species of anchovy from Palau
Taxonomy & Systematics
RAFFLES BULLETIN OF ZOOLOGY 72: 150–161

Date of publication: 2 July 2024
DOI: 10.26107/RBZ-2024-0013
http://zoobank.org/urn:lsid:zoobank.org:pub:6B460459-55B5-416B-9EF0-0617DC4DEEAC

A new species of anchovy, Stolephorus astrum (Teleostei: Clupeiformes:
Engraulidae), from Palau, Micronesia
Harutaka Hata1* & Hiroyuki Motomura2
Abstract. A new anchovy, Stolephorus astrum, new species, is described based on 17 specimens collected from
Babeldaob Island, Palau, Micronesia. The species closely resembles Stolephorus leopardus Hata & Motomura,
2021, Stolephorus pacificus Baldwin, 1984, and Stolephorus teguhi Kimura, Hori & Shibukawa, 2009, in having
a short maxilla (posterior tip just reaching or slightly beyond the anterior margin of the preopercle) and 30 ormore lower gill rakers, but differs from all three in having lower numbers of gill rakers, the pectoral fin without
melanophores, and a combination of a number of other characters.
Key words. Actinopterygii, biodiversity, Caroline Islands, ichthyofauna, Mariana Islands, taxonomy

INTRODUCTION

MATERIAL AND METHODS

The anchovy genus Stolephorus Lacepède, 1803
(Clupeiformes: Engraulidae) currently includes 46 valid
species widespread in the Indo-Pacific region (Whitehead etal., 1988; Wongratana et al., 1999; Kimura et al., 2009; Hata
& Motomura, 2018a–e, 2021a–c, 2022a, b, 2023, 2024a, b;
Hata et al., 2019, 2020a, b, 2021, 2022a, b, 2023; Gangan
et al., 2020). Although the species diversity of Stolephorus
is high in the Southeast Asian region, many species are
distributed in insular areas in Micronesia and Polynesia. These
species, such as Stolephorus multibranchus Wongratana,
1987 (Caroline Islands endemic) and Stolephorus scitulus(Fowler, 1911) (Polynesia endemic), tend to have more gillrakers than their continental congeners, possibly the resultof adaptations enabling efficient capture of the small-sizedplankton dominant in their habitat, surrounded by oligotrophic
waters (Hata & Motomura, 2021). During a revisionary studyof Stolephorus, 17 specimens from Palau, Micronesia were
found to be characterised by numerous gill rakers, and aunique combination of other characters. The new species
is described herein, bringing the number of valid species in
the genus to 47. An identification key to the five species ofStolephorus recorded off Palau is also provided.

Counts and proportional measurements generally followed
Hata & Motomura (2017). All measurements were made withdigital calipers to the nearest 0.01 mm. ‘Pelvic scute’ refers
to a scute associated with the pelvic girdle, and ‘prepelvic
scute’, ‘postpelvic scute’ and ‘predorsal scute’ to hard spinelike scutes anterior to the pelvic scute, posterior to the pelvic
scute, and anterior to the dorsal-fin origin, respectively.
Abbreviations are as follows—SL, standard length; UGR,
LGR and TGR, upper limb, lower limb and total gill rakers,
respectively, with associated numbers indicating the specificgill arch; D–P1, distance from dorsal-fin origin to pectoral-fin
insertion; D–P2, distance from dorsal-fin origin to pelvic-fin
insertion; D–A, distance between dorsal and anal fin origins;P1–P2, distance between pectoral- and pelvic-fin insertions;P2–A, distance from pelvic-fin insertion to anal-fin origin.
Counts and measurements (expressed as percentages of SL)
are given in Tables 1 and 2. Osteological characters wereobserved on soft X-ray photographs. Institutional codes
follow Sabaj (2020).
Availability of data and materials. Morphometric andmeristic data of the species described in this study are
all shown in Tables 1 and 2. Specimen measurements areavailable from the corresponding author upon reasonable
request. All specimens examined in this study have been
deposited in museum collections (see Taxonomy section).

Accepted by: Tan Heok Hui
National Museum of Natural History, Smithsonian Institution, 10th and Constitution
Ave NW, Washington, DC 20560, USA; Email: k2795502@kadai.jp (* corresponding
author)
1

The Kagoshima University Museum, 1-21-30 Korimoto, Kagoshima 890-0065, Japan;
Email: motomura@kaum.kagoshima-u.ac.jp
2© National University of Singapore
ISSN 2345-7600 (electronic) | ISSN 0217-2445 (print)

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Table 1. Meristics of specimens of Stolephorus astrum, new species
Holotype

Paratypes

CAS 230413

n = 1648.1

32.5–54.8

Modes

Dorsal-fin rays (unbranched)

3

3

3

Dorsal-fin rays (branched)

13

12–14

13

Anal-fin rays (unbranched)

3

3

3

Anal-fin rays (branched)

19

18–19

18

Pectoral-fin rays (unbranched)

1

1

1

Pectoral-fin rays (branched)

13

11–14

13

Pelvic-fin rays (unbranched)

1

1

1

Pelvic-fin rays (branched)

6

6

6

Caudal-fin rays

19

19

19

Gill rakers on 1st gill arch (upper)

23

20–24

22

Gill rakers on 1st gill arch (lower)

32

30–34

32

Gill rakers on 1st gill arch (total)

55

50–56

53

Gill rakers on 2nd gill arch (upper)

17

15–18

16

Gill rakers on 2nd gill arch (lower)

29

26–30

29

Gill rakers on 2nd gill arch (total)

46

42–48

46

Gill rakers on 3rd gill arch (upper)

13

12–13

12

Gill rakers on 3rd gill arch (lower)

17

15–17

17

Gill rakers on 3rd gill arch (total)

30

27–30

29

Gill rakers on 4th gill arch (upper)

10

9–10

9

Gill rakers on 4th gill arch (lower)

14

12–14

13

Gill rakers on 4th gill arch (total)

24

21–23

22

Gill rakers on posterior face of 3rd gill arch

6

5–7

6

Prepelvic scutes

3

1–4

4

Scale rows in longitudinal series

35

34–36

35

Transverse scales

8

8

8

Pseudobranchial filaments

18

16–21

18

Total vertebrae

39

38–39

39

Pectoral-fin rays with melanophores

4

2–8

4

Standard length (mm)151

Hata & Motomura: A new species of anchovy from Palau
Table 2. Morphometrics of specimens of Stolephorus astrum, new species
Holotype

Paratypes

CAS 230413

n = 1648.1

32.5–54.8

Modes

Head length

25.0

24.4–27.6

26.1

Body depth

17.6

16.8–19.0

18.1

Pre-dorsal fin length

53.6

50.1–53.4

52.3

Snout tip to pectoral-fin insertion

26.9

26.1–28.7

27.2

Snout tip to pelvic-fin insertion

44.9

43.9–47.1

45.6

Snout tip to anal-fin origin

61.7

59.9–64.2

62.4

Dorsal-fin base length

14.8

13.3–15.8

14.7

Anal-fin base length

20.6

19.8–22.3

21.0

Caudal-peduncle length

17.1

16.8–18.6

17.5

Caudal-peduncle depth

9.7

9.0–10.0

9.4

D–P1

32.6

31.9–34.1

32.9

D–P2

20.1

18.3–20.5

19.7

D–A

20.2

19.1–20.3

19.7

P1–P2

18.8

17.6–20.8

19.4

P2–A

16.1

15.9–18.8

17.5

Pectoral-fin length

16.1

15.9–16.3

16.2

Pelvic-fin length

11.1

10.2–11.3

10.9

Maxilla length

17.6

15.9–17.8

17.0

Mandibular length

16.7

15.9–17.3

16.6

Supramaxilla end to maxilla end

2.4

1.9–3.2

2.5

1st unbranched dorsal-fin ray length

1.5

1.3–2.2

1.8

2nd unbranched dorsal-fin ray length

broken8.2

8.2

3rd dorsal-fin ray length

broken

16.9

16.9

1st unbranched anal-fin ray length

1.2

0.9–1.7

1.3

2nd unbranched anal-fin ray length

5.4

4.8–4.9

5.0

3rd anal-fin ray length

13.7

12.8–13.6

13.4

Orbit diameter

7.8

8.0–9.3

8.7

Eye diameter

6.2

6.5–8.2

7.3

Snout length

4.1

3.8–4.4

4.0

Interorbital width

5.9

5.8–6.6

6.1

Postorbital length

12.5

11.9–13.9

12.9

13.9

12.2–18.0

14.4Standard length (mm; SL)
As % SLAs % of maxilla length
Supramaxilla end to maxilla end

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TAXONOMY

elevating along anal-fin base, thereafter nearly straight(parallel to body axis) to lowermost point of caudal-finbase. Abdomen rounded, covered with one to four (three)spine-like prepelvic scutes anterior to pelvic fin insertion.
Pelvic scute without spine. Postpelvic and predorsal scutes
absent. Anus just anterior to anal-fin origin.

Stolephorus astrum, new species(English name: Astral Anchovy)(Figs. 1, 2A; Tables 1–5)
Holotype. CAS 230413, 48.1 mm SL, ca. 300 yards (approx.
274 m) from mouth of channel draining waters from
Ngeremeskang and Ngkebeduul Rivers, Karamado Bay,
Babeldaob Island, Palau (7°29′47″N, 134°31′31″E), 10 feet
(approx. 3.05 m) depth (water brown, turbid), 7 September
1955, 1630–1730 hours.

Snout round, projecting, length less than eye diameter.
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. Mouth large,
inferior, ventral to body axis, extending backward beyond
posterior margin of eye. Maxilla short, its posterior tip justreaching to or slightly beyond anterior margin of preopercle(just reaching in holotype; just short of anterior margin inparatypes < 36 mm SL). Lower jaw slender.

Paratypes. 16 specimens: 32.5–54.8 mm SL. CAS 230408,
11 specimens, 35.8–54.8 mm SL, KAUM–I. 188269, 43.1mm SL, KAUM–I. 188270, 32.5 mm SL, USNM 445732,
35.3 mm SL, USNM 445733, 34.9 mm SL, 0–50 feet
(approx. 15.2 m) off muddy shore of mangrove estuary in
Kamiyangaru Bay, Babeldaob Island, Palau (7°26′29″N,
134°29′4″E), 2–10 feet (approx. 0.61–3.05 m) depth (water
very muddy; current ca. 0.25–1 knot); CAS 248277, 54.2mm SL, collected with holotype.

Single row of conical teeth on each jaw, palatines, and inneredges of pterygoids. Several conical teeth on vomer. Small
fine teeth patch on pterygoids. No teeth on upper edge ofhyoid arch. Single row of blunt poorly-formed conical teeth
on upper edges of basihyal and basibranchial.

Diagnosis. A species of Stolephorus with the following
combination of characters: maxilla short, 15.9–17.8% of
SL, its posterior tip just reaching to or slightly beyond
anterior margin of preopercle (just short of anterior margin
in individuals < 36 mm SL); posterior margin of preopercle
convex, rounded; no predorsal scutes; prepelvic scutes 1–4(modally 4); pelvic scute without spine; dorsal fin with threeunbranched and 12–14 (13) branched rays; anal fin with threeunbranched and 18 or 19 (18) branched rays, its origin locatedjust below base of ninth to eleventh dorsal-fin ray; 1UGR
20–24 (22), 1LGR 30–34 (32), 1TGR 50–56 (53); 2UGR
15–18 (11), 2LGR 26–30 (29), 2TGR 42–48 (46); 3UGR
12–13 (12), 3LGR 15–17 (17), 3TGR 27–30 (29); 4UGR
9–10 (9), 4LGR 12–14 (13), 4TGR 21–24 (22); gill rakers
5–7 (6) on posterior face of third gill arch; transverse scales
8; pseudobranchial filaments 16–21 (18); total vertebrae 38 or
39 (39); pelvic fin short, 10.2–11.3% of SL, tip of depressed
pelvic fin reaching posteriorly to vertical through 3rd to 6th
dorsal-fin ray origin; pectoral fin short, 15.9–16.3% of SL;
predorsal fin length short, 50.1–53.6% of SL (mean 52.3%);
caudal peduncle rather long, 16.8–18.6% of SL (17.5%);
body slender, 16.8–19.0% of SL (18.1%), distance between
dorsal-fin origin and pelvic-fin insertion 20.1–23.4% of SL(22.0%), between origins of dorsal and anal fins 19.1–20.3%(19.7%); pairs of dark patches on parietal and occipital areas;
no dark lines on dorsum; black spots on tips of snout andlower jaw, but not on suborbital area; melanophores scatteredon 2nd to 8th uppermost pectoral-fin rays.

Posterior margins of preopercle, subopercle and opercle
rounded, smooth. Gill membrane without serrations.
Interorbital space flat. Interorbital 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 open. Isthmus
muscle long, reaching anteriorly to posterior margin of gillmembranes. Urohyal hidden by isthmus muscle (not visible
without dissection). Gill membrane on each side joined
distally, most of isthmus muscle exposed (not covered bygill membrane).
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 closely spaced andunbranched. First dorsal- and anal-fin rays minute. Dorsal
profile of dorsal fin elevated from dorsal-fin origin to third
fin ray tip and lowering to last dorsal-fin ray tip. Anal-fin
origin just below base of ninth to eleventh (tenth) dorsal-fin
ray. Posterior tip of depressed anal fin not reaching caudal-finbase. Uppermost pectoral-fin ray unbranched, inserted below
midline of body. Posterior tip of pectoral fin not reachingvertical through pelvic-fin insertion. Dorsal, ventral, andposterior contours of pectoral fin nearly straight. Pelvic fin
shorter than pectoral fin. Posterior tip of depressed pelvic finreaching to vertical through third to sixth (fourth) dorsal-fin
ray origin. Caudal fin forked, tips of both lobes pointed.

Description. Data for holotype given in parentheses (ifdifferent). Body laterally rather compressed, elongate,
deepest at dorsal-fin origin. Dorsal profile of head andbody gently elevated from snout tip to dorsal-fin origin,
thereafter gradually lowering to uppermost point of caudalfin base. Ventral profile of head and body gently loweringfrom lower-jaw tip to below pectoral fin, thereafter nearlystraight (parallel to body axis) to anal-fin origin, gradually

Body scales deciduous (completely lost in all specimens,
except for prepelvic scutes). Head scales absent. Fins
scaleless, except for broad triangular sheath of scales on
caudal fin.
Colouration of preserved specimens. Body uniformly pale,
light ivory longitudinal band running from just behind upper
opercular margin to caudal-fin base. Pairs of dark patches on
153

Hata & Motomura: A new species of anchovy from Palau

Fig. 1. A, lateral, B, dorsal, and C, ventral views of the holotype (CAS 230413, 48.1 mm SL, Babeldaob Island, Palau), and paratypes(D, CAS 248277, 53.3 mm SL, and E, CAS 248277, 54.8 mm SL (both Babeldaob Island, Palau) of Stolephorus astrum, new species(preserved specimens).

Distribution. The new species is currently known only
from Babeldaob Island, Palau. All of the type specimens
were collected from around river estuaries (see collection
localities).

parietal and occipital regions. No dark lines on dorsum either
anterior or posterior to dorsal fin. Melanophores scatteredalong posterior margin of dorsal scale pockets, tips of snout
and lower jaw, and lateral surfaces of post-temporal region,
and upper part of gill slit, but not on suborbital area. Finrays transparent, colourless. Melanophores scattered along
bases of dorsal and anal fins, and along fin rays of dorsal
and caudal fins and anterior part of anal fin. Melanophores
scattered on 2nd to 8th (2nd) pectoral-fin rays from uppermost
ray (Fig. 2A), gill rakers and gill filaments on first gill arch,gill arch, pseudobranch, and inner side of hyoid arch. Freshcolouration unknown.

Etymology. The specific name ‘astrum’ is given in reference
to the starry black spots on the pectoral fins of the new species.
Comparisons. The new species is assignable to the genus
Stolephorus, as defined by Whitehead et al. (1988) and
Wongratana et al. (1999), having a long isthmus muscle
reaching anteriorly to the posterior margin of the gill
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Fig. 2. Pectoral-fin rays of preserved specimens of A, Stolephorus astrum, new species (CAS 230408, 49.8 mm SL, Babeldaob Island,
Palau; melanophores scattered on 6 uppermost fin rays; left-right inverted) and B, S. pacificus (USNM 263476, 57.8 mm SL, Talofofo
Bay, Guam; no melanophores on pectoral fin).

membrane, the urohyal covered by the isthmus muscle,
possession of prepelvic scutes, and the anal fin originating
just below the middle of the dorsal-fin base, in addition to
the absence of postpelvic scutes.

vertical through the dorsal-fin origin (vs. not reaching)(Wongratana, 1987a; Hata et al., 2021, 2023; Hata &Motomura, 2023; this study).
On the other hand, the new species is differentiated fromthe remaining three species (S. leopardus, S. pacificus, andS. teguhi), which all have higher gill-raker numbers (1TGR
50–56 in S. astrum vs. 57 or more in the others; Table 3).
Moreover, the new species differs from the other three
species in its narrower body [body depth 16.8–19.0% of
SL (mean 18.1%) vs. 17.5–22.2% (19.6%) in S. pacificus,< 19.5% in S. leopardus and S. teguhi; D–P2 18.3–20.5 %of SL (19.7%) vs. 20.1–23.4% (22.0%) in S. pacificus, <22% in S. leopardus and S. teguhi; D–A 19.1–20.3% of SL(19.7%) vs. 19.8–23.0% (21.6%) in S. pacificus, < 21% in
S. leopardus and S. teguhi; Fig. 3A–C], shorter predorsal-fin
length [50.1–53.6% of SL (mean 52.3%) vs. 56.4–57.4%(56.6%) in S. leopardus; 52.9–56.9% (mean 54.3%; lessthan 50% in 2 of 27 specimens ) in S. pacificus; 50.6–57.4%(54.5%) in S. teguhi; Fig. 3D], and longer caudal peduncle[16.8–18.6% of SL (mean 17.5%) vs. 13.8–17.4% (15.6%)
in S. pacificus; > 16.5% in S. leopardus and S. teguhi; Fig.
3E]. Stolephorus astrum further differs from S. leopardus
in having a shorter snout (3.8–4.4% of SL in S. astrum vs.
4.7–4.8% in S. leopardus; Fig. 3F), anal-fin base (19.8–22.3%
of SL vs. 22.4–22.5%; Fig. 3G), D–P1 (31.9–34.1% of SL
vs. 34.6–35.6%; Fig. 3H), postorbital length (11.9–13.9% of

The short maxilla of the new species (posteriorly just reachingor slightly beyond the anterior margin of the preopercle;
just short of anterior margin in individuals < 36 mm SL)
separates the former from the majority of congeners, except
for Stolephorus advenus (Wongratana, 1987), Stolephorus
balinensis (Bleeker, 1849), Stolephorus belaerius Hata,
Lavoué & Motomura, 2021, Stolephorus commersonnii
Lacepède, 1803, Stolephorus horizon Hata & Motomura,
2023, Stolephorus indicus (van Hasselt, 1823), Stolephorus
leopardus Hata & Motomura, 2021, Stolephorus meteorum
Hata, Lavoué, Bogorodsky, Alpermann & Motomura, 2023,
Stolephorus pacificus Baldwin, 1984, Stolephorus scitulus(Fowler, 1911), and Stolephorus teguhi Kimura, Hori &Shibukawa, 2009 (Whitehead et al., 1988; Wongratana etal., 1999; Kimura et al., 2009; Hata & Motomura 2018a–e,
2021a–c, 2022a, b, 2023, 2024a, b; Hata et al., 2019, 2020a,b, 2021, 2022b, c, 2023; Gangan et al., 2020). Among them,S. astrum can be easily distinguished from S. advenus, S.
balinensis, S. belaerius, S. commersonnii, S. horizon, S.
indicus, S. meteorum, and S. scitulus by its higher numbersof gill rakers (1LGR 30 or more in S. astrum vs. 28 or fewer
in the others) and the pelvic fin reaching posteriorly beyond
155

156

n = 23n = 17n = 24n=4n = 23Stolephorus teguhi

Stolephorus astrum, new species

Stolephorus pacificus

Stolephorus leopardus

Stolephorus teguhi

n = 23Stolephorus teguhi

n=4

n=4

Stolephorus leopardus

Stolephorus leopardusn = 24Stolephorus pacificus

n = 24n = 17

Stolephorus astrum, new species

Stolephorus pacificus

n=4

Stolephorus leopardus

n = 17n = 24Stolephorus pacificus

Stolephorus astrum, new species

n = 17

Stolephorus astrum, new species

1

2

72

1

52

57

2

1

56

43

71

51

42

1

50

2

44

6

53

58

4

73

3

54

2

45

1

59

2

55

5

8

46

74

4

56

5

58

1

59

2

60

4

61

5

62

1

2

63

3

76

1

77

1

78

3

1

48

4

49

6

50

4

51

6

60

6

61

2

62

2

63

Total gill rakers on first gill arch (continued)

2

1

47

Total gill rakers on first gill arch (continued)

2

75

Total gill rakers on first gill arch (continued)

557

Total gill rakers on first gill arch (continued)

Table 3. Frequency distribution of longitudinal series of scale rows in Stolephorus astrum, new species, S. pacificus, S. leopardus, and S. teguhi.

3

64

64

3

79

5

52

1

65

2

65

1

1

53

80

66

1

67

66

2

54

81

1

68

1

1

82

55

67

69

70

Hata & Motomura: A new species of anchovy from Palau

30

2

29

2
1

2

2

1

9

3
9

DISCUSSION

1

8

26

1

27

6

28

Furthermore, S. astrum can be distinguished from S.
pacificus by having a shorter pectoral fin (15.9–16.3% of
SL in S. astrum vs. 16.5–18.3% in S. pacificus; Fig. 3K),
with melanophores scattered on 2nd to 8th uppermost
rays (vs. pectoral fin without melanophores; Fig. 2). The
new species differs from S. teguhi in having the anal fin
with fewer branched rays [18 or 19 (modally 18) in S.
astrum vs. 19–21 (20) in S. teguhi; Table 4] and shorterbase (19.8–22.3% of SL vs. 22.7–25.3%; Fig. 3G), shorter
pectoral fin (15.9–16.3% of SL vs. 16.5–18.8%; Fig. 3K),
greater distance from supramaxilla end to maxilla end(12.2–18.0% of maxilla length vs. 6.3–12.2%; Fig. 3J), thedorsum without dark lines (vs. single dark line on dorsum
from occipital region to upper margin of caudal-fin base),and no pigmentation on lateral surface of both upper andlower jaws (vs. melanophores scattered on both jaws) (Hata& Motomura, 2021c; this study; Table 6).

Species of the genus Stolephorus in Palau and Micronesia.
Five species (S. balinensis, Stolephorus bataviensis
Hardenberg, 1933, Stolephorus rex Jordan & Seale, 1926,
and Stolephorus mercurius Hata, Lavoué & Motomura, 2021,
and S. astrum) are known from Palau (supported by voucher
specimens) (Hata et al., 2019, 2021, 2022a). Additionally,
Stolephorus multibranchus Wongratana, 1987 and S. pacificus
have been recorded from the eastern Mariana Islands basedon specimens. Although Myers (1999) reported Stolephorus
apiensis (Jordan & Seale, 1906) from Pohnpei, Caroline
Islands, the 1LGR number given was 32–35, clearly higher
than that given for S. apiensis (28–30) by Hata & Motomura(2018e), but closely matching that of S. multibranchus(1LGR 32–36: Hata & Motomura, 2018c). Because thepaired dark lines on the dorsum of S. multibranchus, a major
diagnostic character (c.f. S. apiensis – no lines on dorsum),are sometimes obscure in some individuals of the former(Hata & Motomura, 2018c: fig. 1B), Myers’s (1999) S.
apiensis was likely a misidentification of S. multibranchus.

4

5

2

n = 23

Wongratana et al. (1999) and Myers (1999) also reported S.
indicus from the Mariana and Caroline Islands referring to
the figure of S. indicus shown in Whitehead et al. (1988).
Although Hata et al. (2021, 2023) and Hata & Motomura(2023) indicated that Whitehead et al.’s (1988) S. indicus
included at least seven species (S. balinensis, S. belaerius,
S. commersonnii, S. horizon, S. indicus, S. meteorum, and S.
scitulus), they did not consider specimens from Micronesia.

Stolephorus teguhi

n=4
Stolephorus leopardusn = 24Stolephorus pacificus

65
n = 17
Stolephorus astrum, new species

22
21
n = 23Stolephorus teguhi

n=4
Stolephorus leopardusn = 24Stolephorus pacificus

4
Stolephorus astrum, new species

n = 17

1

7

5

23

3

1

8

24

Total gill rakers on first gill arch (continued)

5
3
5

5

2
1
1

1
5
6

25

0
1

1

42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27

Total gill rakers on first gill arch (continued)

SL vs. 13.9–14.6%; Fig. 3I), distance from supramaxilla end
to maxilla end (12.2–18.0% of maxilla length vs. 8.1–10.8%;
Fig. 3J), more branched dorsal-fin rays [12–14 (modally 13)
vs. 11 or 12; Table 4] and fewer branched anal-fin rays [18or 19 (18) vs. 19–21 (19); Table 5], dorsum without darklines (vs. single dark line on dorsum from occipital region
to upper margin of caudal-fin base), and no pigmentation onlateral surface of both upper and lower jaws (vs. melanophores
scattered on both jaws).

1

43

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Hata & Motomura: A new species of anchovy from Palau
Table 4. Frequency distribution of branched dorsal-fin rays in Stolephorus astrum, new species, S. pacificus, S. leopardus, and S. teguhi.
Branched dorsal-fin rays
11

12

13

14

Stolephorus astrum, new species

n = 171

14

2

Stolephorus pacificus

n = 262

22

2

Stolephorus leopardus

n=4

1

3

Stolephorus teguhi

n = 23

1

22

Table 5. Frequency distribution of branched anal-fin rays in Stolephorus astrum, new species, S. pacificus, S. leopardus, and S. teguhi.
Branched anal-fin rays
17

18

19

12

5

13

4

Stolephorus astrum, new speciesn = 30Stolephorus pacificus

n = 26Stolephorus leopardus

n=4

3

Stolephorus teguhi

n = 23

10

9

20

21

1
10

3

Fig. 3. Relationships of selected measurements relative to standard length (SL) versus SL or maxilla length in Stolephorus astrum, newspecies (red circles), S. leopardus (yellow diamonds), S. pacificus (blue triangles), and S. teguhi (green squares). A, body depth (as % of
SL); B, distance between dorsal-fin origin and pelvic-fin insertion (D–P2; as % of SL); C, distance between origins of dorsal and anal
fins (D–A; as % of SL); D, predorsal-fin length (as % of SL); E, caudal-peduncle length (as % of SL); F, snout length (as % of SL);G, anal-fin base length (as % of SL); H, distance between dorsal-fin origin and pectoral-fin insertion (D–P1; as % of SL); I, postorbital
length (as % of SL); J, distance between ends of supramaxilla and maxilla [SMX–MX; as % of maxilla length (ML)]; K, pectoral-fin
length (as % of SL).

Therefore, the identification of “S. indicus” sensu Myers(1999) is still unclear.

four species [Stolephorus bengalensis (Dutt & Babu Rao,
1959), Stolephorus eldorado Hata, Lavoué & Motomura,
2022, Stolephorus diabolus Hata, Lavoué & Motomura,
2022, and Stolephorus eclipsis Hata, Lavoué & Motomura,2022], with the nominal species, S. insularis, currently being
regarded as a junior synonym of Stolephorus tri (Bleeker,1852). However, none of these species have been recorded
from Micronesia. Despite the description of S. insularis

Myers (1999) further reported Stolephorus insularis
Hardenberg, 1933 from the Caroline Islands (precise locality
not indicated), referring to the figure of that species shown
in Whitehead et al. (1988). According to Hata et al. (2019,2022c), Whitehead et al.’s (1988) S. insularis in fact included
158

159

19.1–20.3%(mean 19.7%)

15.9–16.3%
3.8–4.4%

D–A (% of SL)

Pectoral-fin length (% of SL)

Snout length (% of SL)

12.2–18.0%(mean 14.4%)

18.3–20.5%(mean 19.7%)

D–P2 (% of SL)

Supramaxilla end to maxilla end(% of maxilla length)31.9–34.1%(mean 32.9%)

D–P1 (% of SL)

11.9–13.9%(mean 12.9%)

16.8–18.6%(mean 17.5%)

Caudal-peduncle length (% of SL)

Postorbital length (% of SL)

19.8–22.3%

50.1–53.6%(mean 52.3%)

Pre-dorsal fin length (% of SL)

Anal-fin base length (% of SL)

16.8–19.0%(mean 18.1%)

Body depth (% of SL)

present

no pigmentation

Pigmentation on jaws

Melanophores on pectoral-fin rays

no lines

18 or 19
(modally 18)

Branched anal-fin rays

Dorsum colouration

12–14 (modally 13)

Branched dorsal-fin rays

Stolephorus astrum

8.1–10.8%

13.9–14.6%(14.2%)

4.7–4.8%

15.6–16.3%

21.2–22.4%

22.4–24.5%

34.6–35.6%(35.2%)

13.9–16.5%

22.4–22.5%

56.4–57.4%(mean 56.6%)

19.5–21.4%

present

scattered on both jaws

single dark line

19–21 (19)11 or 12 (12)Stolephorus leopardus

10.2–16.8% (14.6%)

11.9–14.3% (12.8%)

3.5–4.4%

16.5–18.3%

19.8–23.0% (21.6%)

20.1–23.4% (22.0%)

32.8–37.1% (34.7%)

13.8–17.4% (15.6%)

18.9–22.8%

52.9–56.9%(mean 54.3%;
rarely < 50%)

17.5–22.2%(mean 19.6%)

none

no pigmentation

no lines

17–19 (18)

12–14 (13)Stolephorus pacificus

6.3–12.2%

13.1–15.9% (14.2%)

3.7–4.5%

16.5–18.8%

21.1–23.6%

22.1–25.4%

33.7–38.2% (35.9%)

14.0–16.3%

22.7–25.3%

50.6–57.4%(mean 54.5%)

19.7–22.7%

present

scattered on both jaws

single dark line

19–21 (19, 20)

11 or 12 (12)Stolephorus teguhi

Table 6. Comparison of significant meristics and morphometrics between Stolephorus astrum, new species, S. leopardus, S. pacificus, and S. teguhi (counts and proportions differing significantly
from S. astrum in bold type).

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Hata & Motomura: A new species of anchovy from Palau
ACKNOWLEDGEMENTS

by Myers (1999) being relatively brief, the reference toa golden hue and long maxilla (posteriorly reaching or
extending beyond the preopercular margin) is suggestive ofan unrecognised (undescribed) species, since no species ofStolephorus with such characters has been recorded fromthe Caroline Islands.

We thank T. Vigliotta and R. Arrindell (AMNH), D. Catania
and M. Hoang (CAS), K. Koeda (URM), T. Munroe, J.
Williams, K. Murphy, D. Pitassy, L. Willis, and A. Reft
(USNM), and H. Wada, M. Aizawa, K. Sakamoto, and R.
Ueshima (ZUMT) for opportunities to examine specimensof Stolephorus. We also thank staff of NSMT for theircuratorial assistance, and G. Hardy (Ngunguru, New
Zealand) for reading the manuscript and providing help withEnglish. This study was supported in part by the Sasakawa
Scientific Research Grant from the Japan Science Society(28-745); a Grant-in-Aid from the Japan Society for the
Promotion of Science for JSPS Fellows (DC2: 29-6652);
JSPS KAKENHI Grant Numbers 19K23691, 20H03311,
21H03651, 23K20304; JSPS Overseas Research Fellowships(202160519).

Species of the genus Stolephorus in the Mariana Islands.
With the exception of S. astrum, all species of the genus
Stolephorus recorded from Palau are also widely distributedin Southeast Asia, including the Philippines. However,species of Stolephorus recorded unequivocally from theMariana Islands include only the two endemic species S.
multibranchus and S. pacificus, suggesting the existence ofan ichthyofaunal boundary between Palau and the Mariana
Islands.
Key to species of Stolephorus recorded from Palau

LITERATURE CITED

Data for S. bataviensis and S. balinensis, and S. mercurius and
S. rex, taken from Hata et al. (2019 and 2021), respectively.

Baldwin WJ (1984) Stolephorus pacificus, a new species oftropical anchovy (Engraulidae) from the western Pacific Ocean.
Micronesica, 19: 151–156.
Bleeker P (1849) Bijdrage tot de kennis der ichthyologische fauna
van het eiland Bali, met beschrijving van eentige nieuwe species.
Verhandelingen van het Bataviaasch Genootschap van Kunsten
en Wetenschappen, 22(7): 1–11.
Bleeker P (1852) Bijdrage tot de kennis der Haringachtige visschen
van den Soenda-Molukschen Archipel. Verhandelingen van
het Bataviaasch Genootschap van Kunsten en Wetenschappen,
24(8): 1–52.
Dutt S & Babu Rao M (1959) Occurrence of Anchoviella baganensis
Hardenberg off east coast of India. Current Science, 28:
160–161.
Fowler HW (1911) Notes on clupeoid fishes. Proceedings of the
Academy of Natural Sciences of Philadelphia, 63: 204–221.
Gangan SS, Pavan-Kumar A, Jahageerdar S & Jaiswar AK (2020)
A new species of Stolephorus (Clupeiformes: Engraulidae) fromthe Bay of Bengal. Zootaxa, 4743: 561–574.
Hardenberg JDF (1933) New Stolephorus species of the IndoAustralian seas. Natuurkundig Tijdschrift voor NederlandschIndië, 93: 258–263.
Hata H, Koeda K, Aizawa M, Sakamoto K & Ueshima R (2022a)
A list of Clupeiformes (Actinopterygii: Teleostei) specimens
deposited in the Department of Zoology, The University
Museum, The University of Tokyo. The University Museum,The University of Tokyo, Material Reports, 128: 17–58.
Hata H, Lavoué S, Bogorodsy SV, Alpermann TJ & Motomura
H (2023) A new Stolephorus (Teleostei: Clupeiformes:
Engraulidae: Engraulinae) from the Red Sea. Ichthyology &Herpetology, 111: 191–203.
Hata H, Lavoué S & Motomura H (2019) Taxonomic status of sevennominal species of the anchovy genus Stolephorus described by
Delsman (1931), Hardenberg (1933), and Dutt and Babu Rao(1959), with redescriptions of Stolephorus tri (Bleeker 1852)
and Stolephorus waitei Jordan and Seale 1926 (Clupeiformes:
Engraulidae). Ichthyological Research, 67: 7–38.
Hata H, Lavoué S & Motomura H (2020a) Stolephorus babarani, a
new species of anchovy (Teleostei: Clupeiformes: Engraulidae)
from Panay Island, central Philippines. Zootaxa, 4178(4):509–520.
Hata H, Lavoué S & Motomura H (2020b) Stolephorus acinaces,
a new anchovy from northern Borneo, and redescription of

1. Maxilla short, not reaching to posterior margin of preopercle.
..................................................................................................2– Maxilla long, reaching to posterior margin of preopercle......3
2. 1LGR ≦25; pelvic fin not reaching posteriorly to verticalthrough dorsal-fin origin when depressed............ S. balinensis– 1LGR ≧30; pelvic fin posteriorly beyond vertical throughdorsal-fin origin when depressed............................... S. astrum
3. Dorsum without lines; 1TGR ≦ 38; numerous melanophores
on suborbital area in individuals <56 mm SL... S. bataviensis– Double dark lines on dorsum anterior to dorsal fin; 1TGR ≧39; no melanophores on suborbital area.................................4
4. 1TGR ≧44; head short, 23.1–24.8% SL.............. S. mercurius– 1TGR ≦43; head long, 24.3–27.6% SL.......................... S. rex

CONCLUSION
Stolephorus astrum, new species, is described. The new
species can be distinguished from all other congeners by
its combinations of short maxilla, pigmentation on pectoralfin, and unique range of gill-raker counts. The difference
between species of Stolephorus that occur in Palau (mostspecies are common with those of Southeast Asia) and theMariana Islands (only two endemic species) suggests theexistence of an ichthyofaunal boundary between these areas.
Comparative material examined. Stolephorus leopardus (4specimens: 64.6‒71.5 mm SL): listed in Hata & Motomura(2021c); Stolephorus pacificus: (27 specimens: 28.4‒64.9 mm
SL): listed in Hata et al. (2021c) and one additional specimen:
AMNH 49494, 44.2 mm SL, estuary of Agfayan River,south of Inarajan, Guam (13°16′05.5″N, 144°44′18.1″E);
Stolephorus teguhi: (23 specimens: 40.3‒77.8 mm SL): listed
in Hata et al. (2021c) and one additional specimen: ZUMT
62055, 67.2 mm, Jolo Island, Philippines.

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RAFFLES BULLETIN OF ZOOLOGY 2024
Stolephorus andhraensis (Babu Rao, 1966) (Clupeiformes:
Engraulidae). Marine Biodiversity, 50(6): 1–11.
Hata H, Lavoué S & Motomura H (2021) Taxonomic status ofnominal species of the anchovy genus Stolephorus previously
regarded as synonyms of Stolephorus commersonnii Lacepède
1803 and Stolephorus indicus (van Hasselt 1823), anddescriptions of three new species (Clupeiformes: Engraulidae).
Ichthyological Research, 68(3): 327–372.
Hata H, Lavoué S & Motomura H (2022b) Description of three new
species previously identified as Stolephorus bengalensis (Duttand Babu Rao, 1959) or Stolephorus insularis Hardenberg, 1933,
and a redescription of S. bengalensis (Chordata, Osteichthyes,
Clupeiformes, Engraulidae). ZooKeys, 1121: 145–173.
Hata H, Lavoué S & Motomura H (2022c) A new species ofStolephorus from the eastern Indian Ocean and redescriptionof Stolephorus dubiosus Wongratana, 1983, with comments on
the evolution of prepelvic scute numbers within Stolephorus(Clupeiformes: Engraulidae). Zoological Studies, 61: 58.
Hata H & Motomura H (2017) A new species of anchovy,
Encrasicholina auster (Clupeiformes: Engraulidae), from Fiji,
southwestern Pacific Ocean. New Zealand Journal of Zoology,
44(2): 122–128.
Hata H & Motomura H (2018a) Stolephorus continentalis, a
new anchovy from the northwestern South China Sea andredescription of Stolephorus chinensis (Günther 1880)(Clupeiformes: Engraulidae). Ichthyological Research, 65:
374–382.
Hata H & Motomura H (2018b) First record of the anchovy,
Stolephorus teguhi (Engraulidae) from the Philippines.
Philippine Journal of Systematic Biology, 11: 20–24.
Hata H & Motomura H (2018c) Additional specimens of the poorly
known anchovy Stolephorus multibranchus (Clupeiformes:
Engraulidae) from Kosrae, Caroline Islands. Biogeography,
20: 78–84.
Hata H & Motomura H (2018d) Redescription and distributional
range extension of the poorly known anchovy Stolephorus
nelsoni (Clupeiformes: Engraulidae). Acta Ichthyologica et
Piscatoria, 48: 381–386.
Hata H & Motomura H (2018e) Stolephorus insignus, a new anchovy
from the western Pacific, and redescription of Stolephorus
apiensis (Jordan and Seale 1906) (Clupeiformes: Engraulidae).
Ichthyological Research, 66: 280–288.
Hata H & Motomura H (2021a) Two new species of Stolephorus(Teleostei: Clupeiformes: Engraulidae) from the western Pacific.
Raffles Bulletin of Zoology, 69: 109–117.
Hata H & Motomura H (2021b) Stolephorus grandis, a new anchovy(Teleostei: Clupeiformes: Engraulidae) from New Guinea andAustralia. Zootaxa, 5004: 481–489.
Hata H & Motomura H (2021c) A new species of the anchovy genus
Stolephorus Lacepède 1803 from North Sumatra, Indonesia,
and redescriptions of Stolephorus pacificus Baldwin 1984
and Stolephorus teguhi Kimura, Hori and Shibukawa 2009
(Teleostei: Clupeiformes: Engraulidae). Zoological Studies,60: 65.
Hata H & Motomura H (2022a) Redescription of Stolephorus
ronquilloi Wongratana, 1983 and description of Stolephorus

hindustanensis, a new anchovy from the Western Coast of India(Teleostei: Clupeiformes: Engraulidae). Taxonomy, 2:124–135.
Hata H & Motomura H (2022b) Stolephorus lotus, a new anchovy(Teleostei: Clupeiformes: Engraulidae) from the Northern
Territory, Australia. Zoological Studies, 61: 87.
Hata H & Motomura H (2023) Description of Stolephorus horizonn. sp. from Fiji and Tonga, and redescription of Stolephorus
scitulus (Fowler, 1911) (Teleostei: Clupeiformes: Engraulidae).
Taxonomy, 3: 356–380.
Hata H & Motomura H (2024a) A new species of the anchovy genus
Stolephorus Lacepède 1803, and redescriptions of Stolephorus
carpentariae (De Vis 1882) and Stolephorus holodon (Boulenger
1900) (Clupeiformes: Engraulidae). Ichthyological Research,https://doi.org/10.1007/s10228-024-00971-3.
Hata H & Motomura H (2024b) Redescription and distributional
range extension of the poorly known anchovy Stolephorus
brachycephalus (Teleostei: Clupeiformes: Engraulidae). Natural
History Bulletin of the Siam Society, in press.
Jordan DS & Seale A (1906) The fishes of Samoa. Bulletin of the
Bureau of Fisheries, 25: 173–488 + pls. 33–53.
Jordan DS & Seale A (1926) Review of the Engraulidae, withdescriptions of new and rare species. Bulletin of the Museumof Comparative Zoology, 67: 355–418.
Kimura K, Hori K & Shibukawa K (2009) A new anchovy,
Stolephorus teguhi (Clupeiformes: Engraulidae) from North
Sulawesi, Indonesia. Ichthyological Research, 56: 292–295.
Lacepède BGE (1803) Histoire naturelle des poisons. v. 5. Chez
Plassan, Paris, France, 392 pp.
Myers RF (1999) Micronesian Reef Fishes. A Comprehensive
Guide to The Coral Reef Fishes of Micronesia, 3rd Revised
Edition. Coral Graphics, Guam, 330 pp.
Sabaj MH (2020) Codes for natural history collections in ichthyology
and herpetology. Copeia, 108: 593–669.
van Hasselt JC (1823) Uittrekesel uit een’ brief van Dr. J. C. vanHasselt, aan den Heer C. J. Temminck. Algemeene Konst en
Letter bode voor het Jaar I Deel, 21: 329–331.
Whitehead PJP, Nelson GJ & Wongratana T (1988) FAO Species
Catalogue, vol. 7: Clupeoid Fishes of the World (Suborder
Clupeoidei). An Annotated and Illustrated Catalogue of theHerrings, Sardines, Pilchards, Sprats, Shads, Anchovies andWolf-Herrings. Part 2. Engraulididae. Rome: United Nations
Development Programme/Food and Agriculture Organizationof the United Nations. FAO Fisheries Synopsis, 125: i–viii +305–579.
Wongratana T (1987a) Four new species of clupeoid fishes(Clupeidae and Engraulidae) from Australian waters. Proceedingsof the Biological Society of Washington, 100(1): 104–111.
Wongratana T (1987b) Two new species of anchovies of the genus
Stolephorus (Engraulidae), with a key to species of Engraulis,
Encrasicholina, and Stolephorus. American Museum Novitates,
2876: 1–8.
Wongratana T, Munroe TA & Nizinski MS (1999) Order
Clupeiformes. Engraulidae, Anchovies. In: Carpenter KE &Niem VH (eds.) FAO species identification guide for fisherypurposes. The living marine resources of the western central
Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes,part 1 (Elopidae to Linophrynidae). FAO, Rome, pp. 1698–1753.

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