First record of Macrognathus aral (Bloch & Schneider, 1801) from the Himalayan Kingdom of Bhutan

Laxmi Sagar1,*, Karma Lodhen Wangmo1, Dhan Bdr. Gurung2, Karma Wangchuk3, Rinchen Dorji1, Rupesh Subedi1, Tshering Zangmo1, Pelden Dorji1
Author Information & Copyright
1College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
2Professor, Department of Forest Science, College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
3Lecturer, Department of Food Science and Technology, College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
*Corresponding author: Laxmi Sagar, College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan, Tel: +975-17-924508,

Copyright © 2023 The Korean Society of Fisheries and Aquatic Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Mar 29, 2023; Revised: Sep 05, 2023; Accepted: Sep 06, 2023

Published Online: Dec 31, 2023


This study reports a new record of freshwater fish Macrognathus aral (Bloch & Schneider) from Aiechu-Kalikhola tributary of the Maukhola river in Sarpang, Bhutan. The species was found in shoal of the tributary and was identified using its morphometric characters. It can be identified and distinguished from its congeners reported in Bhutan by dorsal fin rays XIX, 47, anal fin rays III, 52, rostral plates 28, pectoral fin rays 19, caudal fin rays 15, soft rayed part of dorsal and anal fin separated by a notch from rounded caudal fin, and presence of four ocelli at the base of dorsal fins. Further studies are needed to better understand its distribution, ecology, and population dynamics in the country. A key to species belonging to Mastacembelidae of Bhutan including the new record is provided.

Keywords: Aiechu-Kalikhola; Bhutan; Congeners; Macrognathus aral; New record


Bhutan is located in the southern slopes of eastern Himalayas (Caspari et al., 2006) and is a part of 36 global biodiversity hotspots (Myers et al., 2000). The wide spectrum of ecological conditions ranging from subtropics to alpine meadows has endued the country with rich biological diversity including fishes (Gurung & Thoni, 2015). The country is home to 125 fish species (NBC, 2019) under eight orders (Anguilliformes, Beloniformes, Cypriniformes, Perciformes, Salmoniformes, Siluriformes, Synbranchiformes, and Tertadontiformes) and 24 families (Gurung & Thoni, 2015). Majority of the species belong to orders Cypriniformes and Siluriformes holding high significance in economic landscape, aquaculture, and source of animal protein (Gurung & Thoni, 2015; Nikam et al., 2014; Thai et al., 2007). However, species under other orders and families including Matsacembelidae contribute equally to the economic as well as social livelihood in the country.

Family Mastacembelidae under order Synbranchiformes contains spiny eels with elongated body, having 7–40 depressible well-separated dorsal spines, one to three anal spines, body covered with small scales, lack of pelvic fins and girdles, gill openings on later sides of head, short caudal fin with laterally compressed body towards the caudal region (Arunkumar, 2020; Plamoottil & Abraham, 2014). Globally, Mastacembelelidae consist of three genera (Mastacembelus Scolopi 1777, Macrognathus Lacepède, 1800, SinobdellaKottelat & Lim, 1994) distributed in Africa, the Middle East, Southeast Asia, China, Vietnam, and Laos (Nelson et al., 2016; Yuan et al., 2020). Gurung et al. (2013) recognized two genera of spiny eels (Macrognathus and Mastacemblus) from Bhutan.

Based on current records only three species of spiny eels, namely Macrognathus morehensisArunkumar & Singh, 2000, Macrognathus pancalus Hamilton, 1822, and Mastacembelus armatus Lacepède, 1800 are found in inland aquatic habitats of Bhutan (Gurung & Thoni, 2015; NRDCR & LF, 2020). Arunkumar (2016, 2020) recognized the presence of other species of Macrognathus including Macrognathus aral Schneider and Bloach 1801 from transboundary river drainages of Bhutan. However, M. aral has not been reported from Bhutan, but the authors have recorded a single specimen from Aiechu-kalikhola tributary of Maukhola river at Gelephu town under Sarpang district. Apart from the description of the new record, the authors have also developed a comprehensive key to identify species under Mastacembelidae of Bhutan by examining specimens present in the Ichthyology Laboratory, College of Natural Resources (CNR), Royal University of Bhutan (RUB) and comparing pertinent literature (Jayaram, 2010).

Materials and Methods

Specimen collection and preservation

A single specimen of M. aral was collected using Electro shocker (Honda GCV 160cc, Honda, Tokyo, Japan) from 26°53.314’ N, 90°31.187’ E on 16 October, 2022. General water parameters were recorded on site using HACH kit (HQ40d, Hach, Loveland, CO, USA) and riparian vegetation was noted. Additionally, other species associated with M. aral in the tributary was also examined. Following Arunkumar (2020) the color of the specimen was noted while it was fresh and euthanized using 0.2 mL of clove oil per 500 mL of water and treated with 10% formalin (Fernandes et al., 2017). The fixed specimen was preserved in 70% ethyl alcohol and catalogued at the Ichthyology Laboratory, CNR, RUB (RUB/CNR/Fish sample/Aiechu-kalikhola/16.10.2022/223).

Species identification and measurement

Identification of the species by comparing it with existing species from Bhutan and adjacent areas was carried out following ; Arunkumar (2020); Biswas et al. (2007); Gurung & Thoni (2015); Jayaram (2010) ; NRDCR & LF (2020); Shrestha (2008); Vishwanath et al. (2007). Methods followed are those of Jayaram (2010). All the measurements were made with digital caliper to nearest 0.1 mm and expressed as percentage of standard length (SL) (Arunkumar, 2020; Duong et al., 2020). Additionally, for diagnostic, spines and fin rays were counted using microscope (Nikon SMZ445, Nikon, Tokyo, Japan). Standard practices of Jayaram (2010); Ng & Tan (2020); Roberts (1980, 1986) were referred.


Scientific history

The initial documentation of a spiny eel, identified as Rhynchobdella aral, originated from Tranquebar, Tamil Nadu, India (Talwar & Jhingran 1991). The species under genera Macroganthus found in the Indian subcontinent has been consistently referred to as M. aculeatus by nearly all authors (Roberts, 1980). However, there are no type specimens for M. aral (Roberts, 1980). Rhynchobdella ocellata was described from Pondicherry, India which was later considered as secondary junior homonym of M. ocellatus (Kottelat, 2013). Subsequently, a new species of spiny eel (R. ocillata) was described from Tenasseri, Myanmar but was considered incorrect subsequent spelling of M. ocellatus (Kottelat, 2013). Hora (1921) reported a new species of Mastacemblid (R. dhanashorii) from Manipur, India, with the only known holotype which was later declared as an ambiguous synonym of M. aral. Malhotra & Dutta (1975) reported a new species of spiny eel (M. jammuensis) from Jammu, India but was declared as a synonym of M. aral (Talwar & Jhingran, 1991). The current status of the species is valid as M. aral (Arunkumar, 2020).

Diagnostic character

Body elongated eel like, presence of paired tooth plates along the concave ventral surface of rostrum, snout trilobed, rim of anterior nostril with six finger like fimbriae, gape of mouth narrow, jaws with small pointed teeth, pre-orbital and pre-opercular spines absent or smooth, a distinct band on either side of the body above lateral line which becomes obscure in the post-anal region, presence of depressible dorsal spines, anal fin with three spines, caudal fin rounded, the dorsal fin originate much posterior to the pictorial fin, soft dorsal and soft anal fin partially separated by a notch from rounded caudal fin, presence of four ocelli at dorsal fin base, ocellus at base of caudal fin absent. Body count and measurements are shown in Tables 1 and 2 respectively.

Table 1. Meristic characters of the new record (Macrognathus aral) compared with reference data and spiny eels reported from Bhutan
M. aral Macrognathus pancalus Macrognathus morehensis Mastacembelus armatus
Present study Jayaram (2010) Gurung & Thoni (2015) NRDCR & LF (2020) Gurung & Thoni (2015)
Dorsal fin rays XIX, 47 XVI–XXIII, 47–48 XXIV–XXVI, 30–42 XI–XVI, 39–51 XXXIII–XXXX, 67–82
Anal fin rays III, 52 II–III, 44–52 III, 31–46 III, 40–54 III, 67–83
Pectoral fin rays 19 19 17–19 15–20 23
Caudal fin rays 15 15 11–13 11–14 14–17
Rostral plates 28 14–28 Absent 8–11 Devoid
Download Excel Table
Table 2. Morphometric measurements of Macrognathus aral recorded in the present study and compared with reference data
Present study (cm) % of SL Das et al. (2023) (cm)
Total length 23.7 15.7–32.5
Standard length 22.1 14.7–27.2
Head length 3.6 16.5 2.5–4.5
Pre-pectoral length 4.1 18.5 2.7–5.0
Pre-dorsal length 7.5 34.0 5.9–11.0
Pre-anal length 12.9 58.6 9.7–17.9
Base of pectoral length 0.5 2.5 0.3–0.6
Base of dorsal length 8.0 36.2 8.4–15.6
Base of anal length 7.9 36.0 4.8–8.9
Pectoral fin length 1.3 6.2 0.9–1.6
Dorsal fin length 0.9 4.2 0.5–1.0
Anal fin length 0.6 2.8 0.4–0.7
Caudal fin length 1.6 5.2 1.0–1.8
Body depth 2.6 11.7 1.7–3.5
Pre-orbital length 1.9 5.3 1.1–2.0
Post-orbital length 2.1 9.6 1.2–2.2
Eye diameter 0.3 1.3 0.2–0.3

SL, standard length.

Download Excel Table

Fin formula: D. XIX, 47; P. 19; A. III, 52; C. 15 (23.71 cm TL, 22.13 cm SL)

Coloring pattern

Body brownish or greenish, yellowish along the abdomen which becomes lighter below, black shades of caudal, soft dorsal and soft anal fins (Fig. 1).

Fig. 1. Macrognathus aral (Bloch & Schneider, 1801), 22.13 cm SL, caught by electro shocker, 16 October 2022, Aiechu-Kalikhola, Sarpang, Bhutan.
Download Original Figure
Distribution in Bhutan

Currently known to occur only in Aiechu-Kalikhola tributary of Maukhola river under Sarpang district.

Water parameters and habitat type of Aiechu-Kalikhola tributary

Seven water parameters (Table 3) were recorded from the point where the specimen was found. Water temperature (℃), dissolved oxygen (DO) (mg/L), conductivity (S/m), total dissolved solids (mg/L), pH, and salinity (g/kg) were recorded onsite while ammonia (µmol/L) was tested at the Soil Water and Air Testing (SWAT) laboratory, CNR, RUB. The habitat was predominantly subtropical with following floras; Senegalia catechu, Ficus semicordata, Toona ciliate, Bombax ceiba, Ficus racemose, Murraya paniculate, Lantana camara, Urena lobata, Solanum viarum, Chromolaena odorata, Sida acuta, Oxalis corniculate, Borreria latifolia, Piper sp., Synedrella nodiflora, and Cyanotis vaga.

Table 3. Water parameters from the point where new record of Macrognathus aral was found
n Highest Lowest Mean SD
Ammonia (µmol/L) 4 0.0 0.0 0.0 0.0
Conductivity (S/m) 4 226 170 187.5 12.9
DO (mg/L) 4 8.5 7.3 8.1 0.5
pH 4 8.1 7.4 7.7 0.1
Salinity (g/kg) 4 0.1 0.08 0.09 0.007
TDS (mg/L) 4 105.5 78.1 86.8 6.3
Temperature (℃) 4 28.5 25.7 26.7 1.2

n, number of samples; DO, dissolved oxygen; TDS, total dissolved solids.

Download Excel Table
Associated species

A total of 21 species under 10 families (Table 4) were recorded in the Aiechu-Kalikhola tributary where M. aral was found. The most abundant species was Copper mahseer (Neolissochilus hexagonolepis McClelland, 1839) (N = 12), followed by Hamilton’s barila (Opsarius bendelisis Hamilton, 1807) (N = 8) and Giant Daino (Devario aequipinnatus McClelland, 1839) (N = 7) while Glyptothorax botius (Hamilton, 1822) and Golden mahseer (Tor putitora, Hamilton 1822) were the least abundant species (N = 1 each).

Table 4. Associated species with Macrognathus aral in Aiechu- Kalikhola tributary
Species Family N IUCN status
Badis badis Nandidae 3 Least concern
Balitora brucei Balitoridae 2 Near threatened
Batasio batasio Bagridae 2 Least concern
Cyprinion semiplotum Cyprinidae 4 Vulnerable
Danio dangila Danionidae 4 Least concern
Danio rerio Danionidae 2 Least concern
Devario aequipinnatus Danionidae 7 Least concern
Esomus danrica Danionidae 4 Least concern
Garra arupi Cyprinidae 4 Data deficient
Garra birostris Cyprinidae 3 Data deficient
Glyptothorax botius Sisoridae 1 Least concern
Lepidocephalichthys guntea Cobitidae 2 Least concern
Neolissochilus hexagonolepis Cyprinidae 12 Near threatened
Opsarius barna Cyprinidae 5 Least concern
Opsarius bendelisis Cyprinidae 8 Least concern
Paracanthocobitis botia Nemacheilidae 3 Least concern
Pethia conchonius Cyprinidae 6 Least concern
Psilorhynchus homaloptera Psilorhynchidae 2 Least concern
Schistura savona Nemacheilidae 2 Least concern
Tor putitora Cyprinidae 1 Endangered
Xenentodon cancila Belonidae 2 Least concern

IUCN, international union for conservation of nature.

Download Excel Table



The native range of M. aral includes lowland habitats of Indian subcontinent including, Bangladesh, Pakistan, Sri Lanka, Nepal, and Myanmar (Talwar & Jhingran, 1991). In the Indian subcontinent M. aral is uniformly distributed where it holds high significance as food and ornamental fish and is widely used in aquarium trade due to its slender body, attractive color pattern, and playful nature (Abujam et al., 2013; Gupta, 2016). Studies have recognized the presence of M. aral from Northeast India including Assam (Arunkumar, 2016; Dhanze et al., 2018; Gupta, 2016) which shares a close boarder with the current study area making the presence of M. aral highly probable. The preliminary checklist of fishes of Bhutan (Gurung & Thoni, 2015) and fishes of Eastern Bhutan (NRDCR & LF, 2020) have reported M. pancalus and M. morehensis respectively, from the same tributary (Aiechu-Kalikhola). However, there was no confirmation of M. aral from Aiechu-Kalilhola. This study confirms the presence and distribution of M. aral in Aiechu-Kalikhola tributary of Maukhola river in Sarpang district. Additionally, pertinent published literatures have reported the co-occurrence of M. aral and M. pancalus in single river system and basins (Arunkumar, 2020; Talwar & Jhingran, 1991).

Macrognathus aral differs from M. pancalus in a number of features. The most distinguishable taxonomic feature includes the presence of rostral tooth plates in M. aral (Fig. 2) which are absent in M. pancalus (Arunkumar & Singh, 2000), lesser dorsal spines (16–23 vs. 24–26), more soft dorsal fin rays (47–48 vs. 30–42) (Jayaram, 2010), preopercular and pre-orbital spines (absent vs. present) (Talwar & Jhingran, 1991). Similarly, M. aral differs from M. morehensis in many significant taxonomic characters. Data of Arunkumar & Singh (2000) for M. morehensis were used for comparison. It can be easily distinguished from M. morehensis by presence of more rostral plates (14–28 vs. 8–11), more dorsal spines (16–23 vs. 11–16), more caudal fin rays (15 vs. 11–14), pattern of band (longitudinal stripes along entire length vs. 20–25 transverse dark band), and ocellus at the base of caudal fin (absent vs. present).

Fig. 2. Dorsal and ventral visualizations of rostrum in Macrognathus aral. Adapted from Jayaram (2010) with permission of Narendra Publishing House.
Download Original Figure
Identification key to Mastacembelidae of Bhutan
Key to genera

Dorsal fin spines less than 33 (11–26), snout trilobed, ventral surface of rostrum with tooth plates. Rim of anterior tubular nostril with six finger-like projection (Fig. 3A)………………………………………………Macrognathus

Dorsal fin spines 33 or more, no tooth plats in rostrum. Rim of anterior tubular nostrils with two broad-based flaps (Fig. 3B)…..………………………………………….Mastacembelus

Fig. 3. Distinctive nasal structure in Macrognathus and Matacembelus. (A) Rim of anterior nostril with six finger-like projection in Macrognathus; (B) two broad-based flaps in Mastacembelus. Adapted from Jayaram (2010) with permission of Narendra Publishing House.
Download Original Figure
Key to species of Genus Macrognathus

1. Concave ventral surface of rostrum with paired tooth plates………………….………………………………………2

Rostrum globous, without tooth plates………………………3

2. Rostral tooth plates 8–11, Dorsal fin spines 11–16………………………………………….……………………M. morehensis

Rostral tooth plates 14–28, Dorsal fin spines 19–23…………………….…………………………………………………M. aral

3. Caudal fin with 11–13 rays...…………………………………4

4. Dorsal fin spines 24–26 and 30–42 soft rays………M. pancalus

Key to species of Genus Mastacembelus

1. Caudal fin homocercal, confluent with the dorsal and anal fins.

Caudal fin rays 14–16…………………….…………M. armatus

Competing interests

No potential conflict of interest relevant to this article was reported.

Funding sources

Not applicable.


The authors would like to thank Department of Forest and Park Services for granting clearance to collect samples and conduct the study. We would like to thank senior lab in-charges Mr. Sonam Moktan and Mr. Ugyen Tenzin for their assistance during specimen identification. We remain grateful to Mr. Kinga as well, fisherman Gelephu, Sarpang, Bhutan for all the technical and logistic support.

Availability of data and materials

Upon reasonable request, the datasets of this study can be available from the corresponding author.

Ethics approval and consent to participate

This study conformed to the guidance of animal ethical treatment for the care and use of experimental animals.



Abujam SS, Shah RK, Singh SJ, Biswas SP. Food and feeding habit of spiny eel Macrognathus aral (Bloch and Schneider) from upper Assam. J Fish Sci. 2013; 7:360-73


Arunkumar L. Macrognathus siangensis, a new spiny eel from Brahmaputra basin, Arunachal Pradesh, Northeast India (Teleostei: Synbranchiformes). J Res Biol. 2016; 6:2003-12.


Arunkumar L. Review of the spiny eels of Northeast India with description of Macrognathus dhanzei sp. nov. (Teleostei: Synbranchiformes: Mastacembelidae). Int J Fish Aquat Stud. 2020; 8:44-50.


Arunkumar L, Singh HT. Spiny eels of the genus Macrognathuslacepede from Manipur, with description of a new species. J Bombay Nat Hist Soc. 2000; 97:117-22.


Biswas SP, Das JN, Sarkar UK, Lakra WS. Ornamental fishes of North East India: an atlast. Lucknow: National Bureau of Fish Genetic Resources. 2007.


Caspari T, Bäumler R, Norbu C, Tshering K, Baillie I. Geochemical investigation of soils developed in different lithologies in Bhutan, Eastern Himalayas. Geoderma. 2006; 136:436-58


Das M, Mandal S, Bhanja A, Manda B. Morphomeristic characteristics, length-weight relationship, and condition factors of one stripe spiny eel, Macrognathus aral (Bloch and J.G. Schneider, 1801). Res J Agric Sci. 2023; 14:131-8.


Dhanze R, Debbarma P, Debbarma A, Dhanze JR. Biosystematics and distributional status of spiny eel fish species of the genus Macrognathus Lacepede, (Synbranchiformes: Mastacembelidae) from Northeastern region of India. J Entomol Zool Stud. 2018; 6:369-78.


Duong TY, Tran LVD, Nguyen NTT, Jamaluddin JAF, Azizah MNS. Unravelling taxonomic ambiguity of the Mastacembelidae in the Mekong Delta (Vietnam) through DNA barcoding and morphological approaches. Trop Zool. 2020; 33:63-76


Fernandes IM, Bastos YF, Barreto DS, Lourenço LS, Penha JM. The efficacy of clove oil as an anaesthetic and in euthanasia procedure for small-sized tropical fishes. Braz J Biol. 2017; 77:444-50


Gupta S. A note on feeding and reproductive biology of one-stripe spiny eel, Macrognathus aral (Bloch and Schneider, 1801). Int J Res Fish Aquac. 2016; 6:32-4.


Gurung DB, Dorji S, Tsheringi U, Wangyal JT. An annotated checklist of fishes from Bhutan. J Threat Taxa. 2013; 5:4880-6


Gurung DB, Thoni RJ. Fishes of Bhutan: a preliminary checklist. Punakha: Centre for Rural Development Studies. 2015.


Hora SL. Fish and fisheries of Manipur with some observations on those of the Naga Hills. Rec Indian Mus. 1921; 22:165-214


Jayaram KC. The freshwater fishes of the Indian region. India: Narendra Publishing House. 2010.


Kottelat M. The fishes of the inland waters of Southeast Asia: a catalogue and core bibliography of the fishes known to occur in freshwaters, mangroves and estuaries. Raffles Bull Zool. 2013; 27:1-663.


Kottelat M, Lim KKP. Diagnoses of two new genera and three new species of earthworm eels from the Malay Peninsula and Borneo (Teleostei: Chaudhuriidae). Ichthyol Explor Freshwat. 1994; 5:181-90.


Malhotra YR, Dutta SPS. On two new fish species from Jammu along with the checklist of fishes inhabiting Jammu division of J & K state, India. Proc Natl Acad Sci. 1975; 45:153-62.


Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB, Kent J. Biodiversity hotspots for conservation priorities. Nature. 2000; 403:853-8


Nelson JS, Grande TC, Wilson MVH. Fishes of the world. 5th ed Hoboken, NJ: John Wiley & Sons. 2016


NBC. 2019 citation: NBC. Biodiversity statistics of Bhutan. Bhutan: National Biodiversity Centre. 2019.


Ng HH, Tan HH. A new, uniquely patterned spiny eel (Teleostei: Mastacembelidae) from southern Borneo, Kalimantan Tengah, Indonesia. Zootaxa. 2020; 4819:170-8


Nikam DS, Shaikh AL, Salunkhe PS, Kamble AB, Rao KR. Ichthyofaunal diversity of Ashti lake, Tal. Mohol, Dist. Solapur (MS). Glob J Pharm Res. 2014; 3:4-5.


NRDCR & LF. Fishes of eastern Bhutan: species composition and distribution of fishes in the Aiechu, Manas and Nyera-Amachuriver system. Bhutan: DoL, MoAF. 2020.


Plamoottil M, Abraham NP. Macrognathus albus (order: Synbranchiforme; family: Mastacembelidae), a new fish species from Kerala, India. Int J Pure Appl Zool. 2014; 2:100-5.


Roberts TR. A revision of the Asian mastacembelid fish genus Macrognathus. Copeia. 1980; 1980:385-91


Roberts TR. Systematic review of the mastacembelidae or spiny eels of Burma and Thailand, with description of two new species of Macrognathus. Jpn J Ichthyol. 1986; 33:95-109


Shrestha TK. Ichthyology of Nepal: a study of fishes of the Himalayan waters. Kathmandu, Himalayan Ecosphere. 2008.


Talwar PK, Jhingran AG. Inland fishes of India and adjacent countries. New Delhi: Oxford-IBH. 1991.


Thai BT, Si VN, Phan PD, Austin CM. Phylogenetic evaluation of subfamily classification of the Cyprinidae focusing on Vietnamese species. Aquat Living Resour. 2007; 20:143-53


Vishwanath W, Lakra WS, Sarkar UK. Fishes of Northeast India. Lucknow: National Bureau of Fish Genetic Resources. 2007.


Yuan S, Liu M, Zhao Z. Remarkably low genetic diversity and shallow population structure detected of the spiny eel (Sinobdella sinensis) in Eastern China. Genes Genom. 2020; 42:1251-7