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Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

New Record of a Rare Monacanthid, Thamnaconus fijiensis(Tetraodontiformes: Monacanthidae), from Northern Taiwan
Chi-Ngai Tang1
Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan

Corresponding author email: victorcntang@gmail.com

Abstract
A specimen of a rare monacanthid, Thamnaconus fijiensis, was recently caught
off Northern Taiwan, representing the first record from the country. T. fijiensis can be
distinguished from its congeners by the following combination of characters: small,dark-brown spots on the cheek; five longitudinal arrays of spots on the body; a blackishblotch surrounding the anus; and two semi-circular dark bands on the caudal fin.
Keywords: Ichthyology, Monacanthidae, Taxonomy, Thamnaconus fijiensis, NewrecordIntroduction
Members

However, some particularly large-sizedoffamily

species, especially those of the genus

Monacanthidae are small to medium-sized

Thamnaconus, may dwell off continental

tetraodontiform fish with deep and highly

slopes in waters as deep as 450 m

compressed bodies; skin often rough,(Matsuura & Tyle, 1997). In Taiwan, five

shagreen-like, with minute to small scales

species of Thamnaconus have been

armed with one to many fine spinules;

recordedteeth pointed and unfused, and the central

hypargyreus (Cope, 1871), T. modestoides

pair is usually the largest. They possess(Barnard, 1927), T. modestus (Günther,two dorsal fins, the first of which consists

1877), T. septentrionalis (Günther, 1874)

of a prominent spine that can be locked

and T. tessellatus (Günther, 1880). These

upright by a second, very small spine; softspecies are common in local fish markets

rays of the second dorsal fin are

and are caught by trawl-nets, set-nets, orunbranchedhook-and-line. Recently, an unknown(Hutchins,the2001).

Most

monacanthids are found in shallow waters.

(Shen&Wu,2012):

monacanthid was found in a deep-water

77T.

Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

catch bucket at the Keelung Fish Market

converted/transformed to allow for direct(Northern Taiwan), and the fisherman

comparisonsmentioned that this fish was caught byherein (Tab. 1).

tomeasurements

madehook-and-line 80 nautical miles off

Results

Keelung. After comparing the specimen
with previous literatures, it was identified

Thamnaconus fijiensis Hutchins &Matsuura, 1984斐濟短角單棘魨Figs. 1 & 2, Tab. 1

as Thamnaconus fijiensis Hutchins &Matsuura, 1984, a rare monacanthid that issporadically distributed across the Western
Pacific Ocean. This represents the firstrecord of this species in Taiwan, and adetailed description has been presented

Materialexamined.

NMMB-herein alongside images of the collected

P33671 (183.7 mm SL), 80 nautical miles

specimen.

off Keelung, Northern Taiwan, ca. 150–
200 m depth, 30 Apr. 2020.

Methods and materials
Measurements,Description. Dorsal-fin elements II,counts,and33; anal-fin rays 33; pectoral-fin rays 13;

terminology generally follow Hutchinscaudal-fin rays 6+6=12; vertebrate 7(1977) and Hutchins & Matsuura (1984).

(precaudal)+12 (caudal)=19.

Length measurements were taken byBody

strongly

compressedanddigital and common calipers to the nearest

moderately deep, its width 2.1 in HL and

0.1 mm. Standard length (SL) and head

depth 2.6 in SL; head slightly elongated,length (HL) were used throughout, with

its length 3.1 in SL; dorsal profile of snout

other characters’ measurements presented

straight, slightly concave at snout, snout

relative to SL or HL. Osteologicallength 3.8 in SL; orbital diameter 3.8 in HL;characters were observed from X-rays.

interorbital width 3.5; gill slit oblique, its

The lone specimen was deposited in thelength 2.9 in HL, centered below thePisces Collection of National Marine

middle of orbit; pelvis capable of moving

Museum of Biology and Aquarium

vertically, producing a moderate-sized(NMMB-P33671).

forventral flap. Mouth terminal and small;&lips thin, not fleshy; the dentition pattern

Matsuura (1984), Matsuura & Tyle (1997),

comprising three outer and two inner teeth

and Matsuura (1999); in some cases, dataon each side of the upper jaw; extremities

fromof inner teeth projecting between outercomparison

these

Data

used

were from Hutchins

publishedworks

were78

Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

Fig. 1. Fresh (a) and preserved (b) coloration of Thamnaconus fijiensis (NMMB-P33671;
187.3 mm SL) from Northern Taiwan. Please note that the tip of the first dorsal-fin
spine and anal fin were damaged during sampling.
teeth; three teeth on each side of the lower

originating over the center of the orbit; thejaw; extremities of all external teeth inspine armed with four series of downward-

each jaw pointed except the posterior-mostdirected barbs (the anterior face withteeth.

adjoining rows; lateral side of first dorsal-Firstdorsal-finspine

strong,fin spine with a row of strong barbs;
79Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

second dorsal-fin spine hidden in skin afterrays branched except the uppermost andthe first spine; soft dorsal and anal-fin rays

lowermost one; pelvic-fin rudiment non-moderately elevated anteriorly (all rays

mobile, its length 9.8 in HL (2.6 in orbitalthsegmented but unbranched); 8 dorsal-fin

diameter), consisting of two pairs of

ray longest, 2.3 in HL; length of soft

encasing scales fused to the posterior end

dorsal-fin and anal-fin bases 3.0 and 3.4 inof the pelvis, armed with small barbs (Fig.

SL, respectively; origin of anal fin clearly2). Scales on body small, armed withbehind a vertical through origin of the soft

slender and sharp spinules, curving

dorsal fin. Pectoral fin small, its baseslightly posteriorly at extremities; eachslightly posterior to a vertical through themid-body scale with 2‒3 transverse rows

center of the orbit; length of its longest rayof

2.9 in HL; caudal fin length 1.4 in HL, allirregularly).

spinules(sometimes

arrangedFig. 2 Ventral (A) and lateral (B) views of the pelvic fin rudiment of Thamnaconus
fijiensis (NMMB-P33671).

80

Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

Museum accession #NMMB-P33671

USP4541

MNHN1995-528

NMST-P55158

Location

Keelung, Taiwan

Suva, Fiji

New Caledonia

Honshu, Japan

Reference

This study

Hutchins & Matsuura (1984)

Matsuura & Tyle (1997)

Matsuura (1999)

187.3

137 (holotype)102153

Head length

31.9

34

34.233Body depth

38.5

43

41.6*

45

Body width

15.3

1413.913

Snout length

26.2

29

26.6

28

Eye diameter

8.4

10129.3

Interorbital width

9.0-

11.7

11

Gill slit length

10.9111011

1st dorsal spine length

damaged

27

27.1

21

Longest anal raydamaged

-

12.5

9.3

Soft dorsal fin base

33.4

34

34.2

34

Longest soft dorsal fin ray

13.7

13

12.6

8.1

Anal fin base

29.2

29

31.2

28

Inter-dorsal space

29.5

27-

28

Caudal peduncle length

8.0

-

9.8

9.3

Caudal peduncle depth

8.8---

Caudal-fin length

22.1

27

30.6*

20

Pelvic bony structure length

3.3

-

--

Snout to origin of dorsal-fin spine

33.3

-

35.9

-

Lower jaw to rear of pelvic bony structure

61.2

--

-

Pectoral-fin length

10.9

-

13.2

-

Dorsal-fin soft rays

33

33

34

33

Anal-fin rays

33

32

33

32

Pectoral-fin rays

1313;14

13

13

Total caudal-fin rays

1212-

-

7+12=19

7+12=19-

7+12=19

Standard length
morphometric data ( % SL)

Meristic data

Vertebrate

Tab. 1. Morphometric and meristic data of all known specimens of Thamnaconus fijiensis. Data
were converted from number of times in SL or HL to % SL in original description. Charactersfor which different measurement methods from Matsuura & Tyle (1997) were used have been
denoted by asterisks (*).
81

Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

Coloration. Body pale brown whenin gill nets and traps. The Taiwanese

fresh (Fig. 1A). Head with numerous, tiny,

specimen was assumed to be caught below

dark brown spots; two subtle stripes in

200 m (alongside Odontanthias spp. &front of eye which are spotl ess, lips ofBodianus spp).

upper and lower jaw dark. Larger spots onRemarks.

T.

fijiensis

canbebody; those on abdomen are circular,distinguished from most congeners by thegradually fainting downwards. Spots on

numerous dark spots on the lateral sides,

lateral body grouped into patches, forming

thefive longitudinal series; these areas are

tessellatus

yellowish brown. Anus surrounded by aThamnaconus fajardoi Smith, 1953, whichlarge, rounded, dark blotch. Dorsal andalso possess this feature. T. fijiensis

anal fins transparent and faint yellow.

presents a large, black blotch surrounding

Caudal fin with two semi-circular dark

the anus and two semi-circular dark bands

bands. When preserved (Fig. 1B) paleon the caudal fin, in contrast with T.

overall, though spots, blotches, and bands

tessellatus. The dark spots of T. fijiensis

are consistent

with fresh condition.

are often grouped together, forming five

Yellowish pigment within the spots onlongitudinal series. However, this featurebody not evident. Dorsal and anal fin softis also present in T. fajardoi, a deep-waterrays with black pigmentation.

species (130–150 m in the Western Indian

exceptions

being(Günther,Thamnaconus1880)

andDistribution. This species is known

Ocean. Matsuura (1999) mentioned thatfrom scattered localities across the western

the main differences between the two

Pacific Ocean but lacked of record fromspecies: 1) degree of spotting on the bodythe tropical region: Suva Barrier Reef, Fijiand 2) relatively larger body scales in T.

(type locality; Hutchins & Matsuura,

fajardoi. They also noticed1984), New Caledonia (Matsuura & Tyler,that the spots on the cheeks of T. fijiensis

1997), Shirahama, Honshu (Matsuura,

are much smaller, and the two series of1999) and Ogasawara (Nakabo, 2012) indark spots on the dorsum are straight (vs.

Japan, and northern Taiwan (this study).

curved in T. fajardoi). These characters are

Although the distribution pattern is

consistent with the Taiwanese specimen.

tempting to claim that this species isThree records of T. fijiensis have been

antiequatorial, more thorough equatorial

documented (Tab. 1), each presenting asampling efforts are needed. This speciessingle specimen: Hutchins & Matsurra

inhabits deep-water, rocky reefs at depths(1984), Matsuura & Tyle (1997), and150–210 m (Matsuura, 1999) and is caught

Matsuura82(1999).

TheTaiwanesePlatax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

specimen is the largest among them (187.3

being said, meristic counts of the four

mm SL). The other three specimens (102–specimens did not differ greatly; dorsal-fin,

153 mm SL) included young and mature

anal-fin soft rays, and pectoral-fin rays

individuals, though the relative lengths ofranged from 33–34, 32–33, and 13–14,

several morphometric characters differ

respectively.

(Tab. 1). Of note, the orbital diameter tends

Acknowledgements

to decrease with body size (Fig. 3).
However, the first dorsal-fin spine of theThis

study

wassupportedby

Taiwanese specimen was damaged, andNational Museum of Marine Biology &the body depth of the New Caledonia

Aquarium, Pingtung (NMMBA), and thespecimenwas

National Museum of Marine Science andmeasured in a different way (see Tab. 1.).

Technology, Keelung (NMMST). The

More specimens must be analyzed toauthor is grateful to H.-C. Ho (NMMBA)

better understand the degree of variation inand S.-C. Wang (NMMST) for guidance,

the morphological characteristics assessedand C.-H. Chan (NMMBA) for curatorial

across individuals, gender, age, etc. Thatassistance.

(MNHN1995-528)

12.5

Orbital diameter (in % SL)

12.0
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0

80

100120

140

160

180

Standard length (mm SL)
Fig. 3. Relationship between orbit diameter and standard length (SL).

83200

Platax 17: 77-84, 2020
doi: 10.29926/platax.202012_17.0005

Matsuura, K. & J.C. Tyler, 1997.
Tetraodontiform fishes, mostly fromdeep waters, of New Caledonia. No. 9. In:Séret, B. (ed.) Résultats des Campagnes
MUSORSTOM, 17. Mémoires duMuséum National d'Histoire Naturelle,Paris (N. S.) (Série A) Zoologie,
174:173-208.
Matsuura, K. 1999. First record of the rare
filefish,Thamnaconus
fijiensis(Tetraodontiformes:Monacanthidae)
from Japan. Ichthyological Research,46(2):216-218.
Nakabo, T. 2012. Fishes of Japan with pictorial
keys to the species, 2nd edn. TokaiUniversity Press, Tokyo, Japan.
Shen, S.C. & K.Y. Wu. 2011. Fishes of Taiwan.
National Museum of Marine Biology &Aquarium, Checheng, Taiwan.

References
Hutchins, J.B. 1977. Descriptions of three newgenera and eight new species ofmonacanthid fishes from Australia.
Records of the Western AustralianMuseum, 5(1):3-58.
Hutchins, J.B. 2001. Order Tetraodontiformes,Monacanthidae. In: Carpenter, K.E. &V.H. Niem (eds.). Food and Agriculture
Organization(FAO)
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Identification Guide for Fishery
Purposes: The Living Marine Resourcesof the Western Central Pacific, Vol. 6.
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