Branchiostegus biendong, Hiramatsu & Vinh & Endo, 2019

Hiramatsu, Wataru, Vinh, Chu Tien & Endo, Hiromitsu, 2019, Branchiostegus biendong, a New Tilefish from Vietnam (Perciformes: Branchiostegidae), Zootaxa 4661 (1), pp. 133-144 : 134-141

Branchiostegus biendong new species

New English name: Yellow-blotched tilefish

( Figures 1–4 ; Tables 1–3 )

Holotype. VNMN-F 2017 . 001, (formerly BSKU 54028 ), 209 mm SL, male, off Quy Nhon (collected from a local fish market of Quy Nhon), 16 June 1997, southern coast of central Vietnam, purchased by W. Hiramatsu.

Paratypes. BSKU 54029, 181 mm SL, male ; NSMT-P 130013 (formerly BSKU 54030 ), 181 mm SL, sex undetermined, both collected with the holotype .

Diagnosis. A species of Branchiostegus distinguished from all congeners by the following combination of characters: cheek scales in six diagonal rows exposed, their size moderately large 2.2–2.5 % SL; predorsal ridge black; cheek almost silver with oval-shaped, yellow blotch along ventral rim of eye; dorsal fin translucent yellowish with black stripe overlapping yellow coloration along dorsal margin; upper lobe (two thirds) of caudal fin with 5–6 yellow horizontal stripes and tip with black blotch; lower third of caudal fin navy blue.

Description. Data for the holotype are presented first, followed by those of the paratypes in parentheses. Counts and proportional measurements are shown in Table 1 .

Body elongate, moderately compressed. Head moderately large, 3.3 (3.4–3.5) in SL. Body depth at the dorsalfin origin 3.8 (3.8–3.9) in SL. Weak predorsal ridge extending anteriorly. Mouth terminal, oblique, distal end of upper jaw reaching to about a vertical through midpoint of orbit. Orbit close to the margin of forehead, its diameter moderately large, 3.6 (3.4–3.5) in HL, longer than suborbital depth. Two nostrils located about half way between snout and anterior margin of eye; anterior nostril forming into a tube with tongue-shaped flap at posterior margin; posterior nostril oval-shaped hole without fleshy flap. Jaws with an outer series of canine-like teeth and inner villiform tooth band: canine-like teeth comprising 15 (14–17) on upper jaw, those at symphysis and distal end enlarged, 6 (9 or 10) on lower jaw, lining its posterior half, enlarged near end; villiform tooth band comprising 3–4 (2–3) irregular rows on upper jaw, becoming narrower posteriorly, 1 or 2 rows at distal end, 4 (3 or 4) irregular rows at symphysis, becoming narrower posteriorly, 2 rows at the distal end; no teeth on vomer and palatine. Margin of preopercle finely serrated posteriorly, strongly at angle, rather smooth ventrally.

Head and body scaled except for snout, forehead, and suborbital area; scales cycloid on cheek, opercle, pectoral inner corner, and breast; ctenoid elsewhere; six diagonal scale rows on cheek; scales slightly enlarged in the middle row; diameter of largest cheek scales 3.3 (3.7–4.0) in OD. Dorsal-fin origin above pectoral-fin base; 1st spine shortest, 1.5 (2.0–3.0) in OD; 2nd 0.9 (0.9–1.1) in OD, remainder gradually become longer posteriorly, 7th spine longest, 0.9 (0.8) in OD; dorsal-fin soft rays except 15th soft ray longer than all spines, 1st soft ray about 0.7 (0.7–0.9) in OD, becoming longer posteriorly to 13th soft ray; 13th dorsal-fin soft ray longest, extending to caudal-fin base, 0.4 in OD, 14th and 15th soft rays rapidly decreasing in length compared with 13th; 12th, 14th and 15th soft rays not reaching caudal-fin base. Anus located at about midpoint of body or slightly posterior. Anal-fin origin slightly posterior to anus; anal-fin spines short, 1st spine 2.5 (3.0–3.1) in OD, 2nd spine 1.3 (1.3–1.5) in OD; anal-fin soft rays gradually increasing in length posteriorly until 11th soft ray, 1st soft ray 0.9 (0.8–0.9) in OD, 11th soft ray longest, 0.6 (0.5) in OD; tip of longest anal-fin soft ray reaching just above caudal-fin base. Pectoral fin lanceolate, its base located just posterior to preopercle margin, extending posteriorly beyond anus, not to anal-fin origin; 1st pectoralfin ray length equal to OD, upper seven gradually increasing in length to longest 7th soft ray, 0.3 (0.4) in OD, 8th soft ray considerably shorter, 0.5 in OD. Pelvic fin wedge-shaped, its length shorter than 13th dorsal-fin soft ray, reaching posteriorly to about the midpoint between pelvic- and anal-fin origins; second pelvic-fin soft ray longest. Caudal peduncle somewhat deep, its depth 2.4 (2.3–2.4) in BD. Caudal fin double emarginate.

Color when fresh ( Fig. 1 ). Based on color transparencies of the holotype and two paratypes. Body pinkish dorsally, gradually changing in color toward ventral area, becoming glint silver on belly. Snout pale pink. Cheek silvery or pinkish silver with oval-shaped, oblique yellow blotch along posteroventral rim of eye. Interorbital area silver with tinge of yellow. Predorsal ridge dark. Dorsal fin translucent yellowish with narrow black margin extending from 1st spine to 7th soft ray in holotype (to 12th soft ray in two paratypes); yellowish tinge stronger dorsally and overlapped with black margin. Anal fin translucent entirely except for white along base. Pectoral fin semi-transparent. Pelvic fin almost white. Caudal fin with 5–6 yellow horizontal stripes on upper two-third with white interspaces; a black blotch on postero-dorsal corner; upper two-third with white margin; two middle of which extending over caudal peduncle; navy blue blotch on lower one-third; caudal-fin base yellow with a reddish tinge.

Color in alcohol. Body almost light yellow. Dorsal-fin membrane translucent bordered with dark. Pectoral fin translucent with dark posteriorly. Pelvic and anal fins semi-transparent. Caudal fin upper two thirds yellowish with light yellow stripes, and dark gray on lower one third.

Distribution. Currently known from Quy Nhon and Nha Trang on the southern central coast of Vietnam (South China Sea).

Etymology. Named after the R/V “Biển Dộng” belonging to the Research Institute of Marine Products, Minis- try of Fishery (currently Research Institute for Marine Fisheries, Hai Phong), which was used for the study of fish resources in the South China Sea. In addition, in Vietnamese, “ biendong ” alludes to the South China Sea where the type specimens were collected. The new English name, Yellow-blotched tilefish, is named after the yellow ovalshaped blotch under the eye, which is one of the distinguishable characters.

Comparisons. Branchiostegus biendong is most similar to B. wardi from the eastern coast of Australia in having yellowish dorsal-fin membrane, a silver cheek with a yellow blotch instead of a yellow marking or bar, and several yellow stripes on the caudal fin, but clearly differs in having larger cheek scales (their diameter 2.2–2.5% SL vs. 1.2–1.9% SL), six cheek scale rows (vs. 10–11), the dorsal fin with black margin (vs. entirely yellowish), the caudal fin with 5–6 yellow stripes (vs. two central yellow stripes), and a black blotch at the tip of the upper caudal fin (vs. black blotch absent) ( Table 3 ; Whitley 1932; Dooley 1978, 1999; Dooley & Kailola 1988).

Further, B. biendong resembles B. auratus in having a vivid pink dorsum with somewhat yellowish head, a black predorsal ridge, a yellowish dorsal-fin membrane, and several yellow stripes on the caudal fin, but clearly differs in having the following combination of characters except the cheek scale ones mentioned above: cheek silver with an oval-shaped, yellow blotch below the eye (vs. entirely yellow with a silver bar extending from the ventral rim of the eye to the upper lip); anal fin translucent (vs. grey excluding translucent area along the base); a black blotch at the tip of the upper caudal-fin lobe (vs. absent); and the lack of a row of yellow spots along the most ventral stripe (vs. present) ( Tables 2 , 3 ; Yoshino et al. 1984; Aizawa & Doiuchi 2013).

The new species resembles only B. okinawaensis in having 5–6 rows of large cheek scales (including their largest size of 2.2–3.3 % SL), while other congeners usually have 8–12 rows of smaller scales (1.2–2.2 % SL; Table 2 ). However, the new species is readily distinguished from B. okinawaensis in having a relatively small head 28.8–29.9 % SL (vs. 30.3–33.3 % SL), the cheek with a yellow blotch below eye (vs. no markings), the dorsal fin with black margin (vs. with an olive-drab blotch between 1st and 3rd spines), 5–6 yellow stripes on the caudal fin (vs. two yellow central stripes with a dark interspace), and a black blotch at the tip of upper caudal fin (vs. absent) ( Tables 2 , 3 ; Hiramatsu & Yoshino 2012).

Branchiostegus biendong somewhat resembles the three Eastern Asian species, B. japonicus , B. argentatus , and B. albus , in having similar body colorations: viz., pinkish dorsally and silver ventrally, reddish pink or yellowish dorsal fin, and several yellow stripes on the caudal fin. However, excluding cheek scale ones above-mentioned, the new species differs from them in having the following combination of characters: a yellow blotch along the ventral rim of the eye (vs. absent in the latter three), dorsal fin with narrow black stripe overlapping yellow coloration along dorsal margin (vs. absent), and a black blotch on the tip of the upper caudal-fin lobe (vs. absent) ( Figs. 2 , 3 , 4 ; Tables 2 , 3 ). Additionally, B. biendong is distinguished from B. japonicus in having cheek scales not covered with skin (vs. covered with skin); B. argentatus in having large head 28.8–29.9 % SL (vs. 26.5–26.7 % SL) and short 1st dorsal-fin spine 4.4–5.3 % SL (vs. long, 9.0–9.1 % SL); B. albus in having 2nd pelvic-fin soft ray longest (vs. 3rd longest), pelvic fin shorter than 13th dorsal-fin soft ray (vs. longer than 13th dorsal-fin soft ray), and predorsal ridge black (vs. white) ( Tables 2 , 3 ).

In the western North Pacific, three natural hybrids among four species of Branchiostegus have been rarely reported from the East China Sea, the Bungo Channel, and the Hyuga-nada Sea (W. Hiramatsu, pers. comm.), Japan: i.e., B. japonicus x B. auratus , B. japonicus x B. argentatus , and B. japonicus x B. albus ( Yamada et al. 1998, 2000, 2007; Yamashita et al. 2013). Also, an unpublished hybrid of B. albus x B. auratus has also found (J. Dooley, pers. comm.). Among the parent species, B. japonicus is the most abundant and widely occurs from shallow to deep bottoms, and its habitat mostly overlaps those of the others in depts of 20–270 m ( Yamashita et al. 2013).

For the external features, these hybrids usually possess both characteristics from the parent species: i.e., B. japonicus x B. albus has yellowish pink cheek lacking silver bars and blotches, dark large pelvic fin, caudal fin with pale yellow stripes and spots, and dark predorsal ridge; B. japonicus x B. argentatus has one silver bar below eye, one silver wavy marking behind eye, no yellow blotches on body, and a series of faint dark blotches on dorsal fin; and B. japonicus x B. auratus has reddish cheek with one silver bar below eye and one silver, triangle-shaped blotch behind eye, cheek scales exposed or covered with thin skin, yellowish translucent dorsal-fin membrane except for whitish anterior, an indistinct yellow blotch on the middle of the body, and yellow spots on lower lobe of caudal fin (but sometimes lost). Concerning the hybrid of B. japonicus x B. auratus , morphometric and nuclear DNA analyses by Yamashita et al. (2013) demonstrated that two specimens were indeed a mixture and intermediate of the two parent species. In the South China Sea, off Vietnam, B. biendong can be distinguished from the known hybrids by color patterns and the number of diagonal cheek scale rows, i.e., pale pink to silver cheek with a yellow blotch below eye, yellowish dorsal fin with black stripe along the dorsal margin, black blotch on the dorsal tip of caudal fin, and 6 cheek scale rows in B. biendong (vs. 8–10 in the others, but the counts of the hybrids are unknown).

Remarks. The first species of Branchiostegus reported from Vietnam was “ Latilus tollardi Chabanaud, 1924 ”, described as new on the basis of a single specimen collected from central Vietnam ( Annam). Later, Kuronuma (1961) listed B. tollarai (misspelling of B. tollardi ) and B. argentatus (not Cuvier 1830) in A check list of Fishes of Vietnam giving the Japanese names “Amadai” and “Shiroamadai” to these two species respectively. Several years later, Fourmanoir (1965) recorded B. sericeus (misspelling of B. sericus Herre, 1935 ), with a line drawing, from Nha Trang in southern Vietnam. Fourmanoir (1965: 49, fig. 28), clearly illustrated B. argentatus with two bars on cheek, a row of black blotches on the dorsal-fin membrane, and two stripes on the sides of the body.

In an extensive review of the family, Dooley (1978) reviewed all nominal species of Branchiostegus , and synonymized both B. tollardi and B. sericus under B. argentatus ( Cuvier, 1830) based on the examination of their types. Additionally, Dooley (1978) pointed out that all Japanese ichthyologists had long been incorrectly applying the name “ B. argentatus ” reported by Temminck & Schlegel (1846) to a species newly described in his paper as B. albus . Dooley (1978) also recorded B. japonicus from off central Vietnam (15˚40'N, 109˚25'E, off Quang Ngai) on the basis of museum collections.

Muda et al. (2001) listed four species of Branchiostegus from Vietnam: B. albus (244 mm TL) from Nha Trang in southern Vietnam, B. argentatus (307 mm TL) from Da Nang in central Vietnam and two unidentified species from Da Nang and Cut Ba in central and northern Vietnam. In the following year, three species, B. argentatus , B. auratus , and B. japonicus , were reported from the Spratly (= Nansha) Islands, which are about 500 km from the southern coast of Vietnam (Chen et al. 2002: 28, figs. 80–82). Of these, B. japonicus is currently known from off central Vietnam, Hainan Island in the South China Sea, along the coast of China, Taiwan in the East China Sea, South Korea, from northern Kyushu and central Honshu Islands facing the Japan Sea north to the Tsugaru Strait ( Dooley 1978, 1999; Kim & Ryu 1984; Shen 1984, 1994; Dooley & Kailola 1988; Aizawa & Doiuchi 2013). Additionally, B, auratus shows a similar distributional range in the northern South China and East China Seas, Japan Sea and western Pacific Ocean, from Hainan Island and Hong Kong, Canton along the coast of China, to Taiwan, South Korea, and southern Japan ( Dooley 1978, 1999; Kim & Ryu 1984; Shen 1984, 1994; Yoshino et al. 1984; Yamada et al. 2007; Aizawa & Doiuchi 2013). For B. japonicus and B. auratus , this report therefore refers to their southernmost and first reliable records from the southern South China Sea. Although J. K. Dooley (pers. comm.) made efforts to find these two species in fish markets in the Philippine Islands, South China Sea, south to Hainan Island and the coast of Vietnam, he was unsuccessful. Accordingly, he noted that the records of B. japonicus and B. auratus in the South China Sea south to Taiwan including the Vietnamese coast are doubtful. Recently, Kimura et al. (2018) reported B. albus and B. argentatus with excellent color photographs from Ha Long Bay. Hence, three species, B. argentatus , B. albus , and B. biendong are currently known from the coast of Vietnam. Additionally, considering the reliable record of B. japonicus and B. auratus from the Spratly Islands, we consider that they potentially occur in Vietnamese waters.

Branchiostegus biendong was initially known only from Quy Nhon in southern central Vietnam in the South China Sea. In October 2016, one specimen of the species was collected and photographed at a fish market in Nha Trang, which is located south of Quy Nhon ( Fig. 3 ; Naohide Nakayama, pers. comm.). Further, we searched websites to gather information regarding the occurrences of tilefishes from Vietnam. As a result, we found several photographs of different tilefishes in a few weblogs, which were taken at a local fish market of Da Nang on the central coast of Vietnam. Some of them agree well with B. biendong in having the yellow blotch below the eye, 5 or 6 yellow stripes on the upper two thirds of the caudal fin, and one black blotch on the upper lobe of the caudal fin. It is probable that the new species is common and landed commercially in the area along with B. albus and B. argentatus . The latter two species show a similar distributional pattern, ranging widely from the South and East China Seas (including Vietnam, Hong Kong, Hainan Island, Taiwan, China and southern Korea) to southern Japan (including southern Honshu, Shikoku and Kyushu islands) ( Dooley 1999; Kim & Ryu 1998; Matsuura et al. 2001; Aizawa & Doiuchi 2013). Considering the previous records from Vietnam (i.e., Cut Ba, Haiphong, Da Nang, Quy Nhon, and Nha Trang), B. biendong may be widely distributed along the Vietnamese coast (Chabanaud 1924; Kuronuma 1961; Fourmanoir 1965; Muda et al. 2001).

Branchiostegus ilocanus Herre, 1928 was originally described on the basis of a single specimen (270 mm long) collected at a fish market in Narvacan, Ilocos, Luzon Island, Philippines, but has been regarded as nomen dubium ( Dooley 1978; Dooley and Iwatsuki 2012). Although Herre (1928) did not note the whereabouts of the holotype, Dooley 1978 reported that it would have been destroyed in the Philippines during World War II. Regarding cheek scales, Herre (1928: 33, pl. 3) illustrated B. ilocanus uniquely with three large central scales. The new species, B. biendong , is readily distinguished from B. ilocanus in having 6 scale rows on the cheek (vs. 8), a somewhat small head 28.8–29.9 % SL (33.3 % SL), a double-emarginate caudal fin (vs. truncated), a silver cheek with an oval-shaped yellow blotch along the ventral rim of the eye (vs. yellow with an orange spot on the lower part of the snout), 5–6 yellow stripes on the caudal fin (vs. one central yellow stripe), and a black blotch at the tip of the upper lobe of the caudal fin (vs. absent) ( Herre 1928; Dooley 1978; Hiramatsu & Yoshino 2012).

Figures

FIGURE 1. Branchiostegus biendong n. sp., in fresh, VNMN-F 2017. 001, holotype, male, 209 mm SL., Quy Nhon, Vietnam, photographed by W. Hiramatsu.

FIGURE 2. Line drawing of Branchiostegus biendong n. sp., VNMN-F 2017. 001, holotype, male 209 mm SL, Quy Nhon, Vietnam, drawn by W. Hiramatsu. Dotted line indicates posterior margin of anus.

FIGURE. 3. Branchiostegus biendong n. sp., in the local fish market of Nha Trang, Vietnam, Photographed by N. Nakayama (20 Dec. 2016).

FIGURE. 4. A. Branchiostegus albus, BSKU 92864, 224 mm SL, B. Branchiostegus japonicus, BSKU 92582, 231 mm SL, collected from Tosa Bay, Japan. Photographed by N. Nakayama.