Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 February 2023 | 15(2): 22749–22751
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.7985.15.2.22749-22751
#7985 | Received 24
April 2022 | Final received 29 November 2022 | Finally accepted 18 December
2022
Photographic record of the
butterfly ray Gymnura cf. poecilura (Myliobatiformes: Gymnuridae) from the Bhagirathi-Hooghly River in West
Bengal, eastern India
Priyankar Chakraborty
Sundarban Tiger Widow Welfare Society
(STWWS), Arampur, Gosaba,
West Bengal 743370, India.
Editor: Simon Weigmann,
Elasmobranch Research Laboratory, Hamburg, Germany. Date of publication: 26 February 2023 (online &
print)
Citation: Chakraborty, P. (2023). Photographic record
of the butterfly ray Gymnura cf. poecilura (Myliobatiformes: Gymnuridae) from the Bhagirathi-Hooghly River in West
Bengal, eastern India. Journal of Threatened Taxa 15(2): 22749–22751. https://doi.org/10.11609/jott.7985.15.2.22749-22751
Copyright: © Chakraborty 2023. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: The author has received no financial support for the research, authorship, or publication of this article.
Competing interests: The author declares no competing interests.
Acknowledgements: I would like to thank the fisher
who provided me with valuable information and gave me permission to use this
information together with the photographs. I would also like to thank the
reviewers and editors for their careful review of my manuscript and their
insightful remarks and suggestions.
Most elasmobranchs are marine,
but some (euryhaline) species occur regularly in estuaries and lower reaches of
rivers, and some are obligate freshwater species (Lucifora
et al. 2015). Stingrays (some species of Dasyatidae
and most of Potamotrygonidae) have been recorded in
freshwater habitats (Compagno & Roberts 1982; Weigmann 2016).
Butterfly rays, family Gymnuridae, comprise a single genus Gymnura
van Hasselt, 1823 and are generally marine, although sometimes found in
brackish water areas (McEachran & Carvalho 2002).
It includes 12 valid species found in the Indo-Pacific and the Atlantic Oceans
(Yokota et al. 2016). Globally, three Gymnura
species are marginal, and one is brackish marginal (Martin 2005).
Records of elasmobranchs from the
freshwater reaches of the Ganges go back centuries. Hamilton (1822) described
rays (called “skates”) occurring far away from the tidal reaches of the river.
At present, rays are a rare bycatch in parts of the freshwater reaches of the
Ganges in West Bengal (author pers. obs. 14.vi.2012; 7.i.2018; 22.i.2022).
During a pilot survey of riverine
elasmobranchs in West Bengal, eastern India, a fisher showed photographs of a
“Shankar Maach” (local name for stingray) that he had
caught in a set net. He said he had caught the fish in April 2019 from the
Bhagirathi-Hooghly River, a tributary of the Ganga (22.3110N, 88.0940E)
near Barkolia village in Howrah district of West Bengal
(Figure 1). He stated that the fish weighed about 8.5 kg and had a disc width
of about 90 cm (Image 1). The fish was subsequently identified from the
photographs as a gymnurid ray based on its unique body shape with a strongly
depressed body and pectoral fins extending into a “lozenge-shaped” disc, and as
Gymnura cf. poecilura
(Shaw, 1804) based on its long tail with 13 black bands and lack of a dorsal
fin (Yokota et al. 2016). The fisher stated that he and his family had eaten
the fish. As the species was only recognised from
photographs, the specific name is preceded by the qualifier ‘cf’.
The nearest marine environment
from which gymnurids have been reported is over 100 km away in Digha (Yennawar et al. 2017), and
they have also been listed in the mangrove-lined brackish waters of the
Sundarbans in southeast West Bengal (Mishra et al. 2019), which is also a
considerable distance from the capture site of this study. Therefore, this
study reports the first occurrence of Gymnuridae,
i.e. Gymnura cf. poecilura,
from the Bhagirathi-Hooghly River in West Bengal and India’s first Gymnuridae so far inland. A separate species of Gymnura, also referred to as G. cf. poecilura, occurs in the northern Arabian Sea (Muktha et al. 2016). However, it is unlikely that the
specimen in this study is G. cf. poecilura
(sensu Muktha et al. 2016),
as it was captured from a tributary of the Ganga that flows into the western
Bay of Bengal.
Although the identification of
the species is based on only two photographs, this evidence is crucial as G.
poecilura is listed as Vulnerable by the
International Union for the Conservation of Nature (IUCN) Red List, and its
current population trend is reported to be in decline (Sherman et al. 2021).
This study shows how fishers’ knowledge can help fill information gaps about
rare riverine elasmobranchs.
Thus, this study helps direct
future research to document the diversity of elasmobranchs in Indian rivers and
to understand how they use their non-marine habitats. It is also important to
study the impact of fishing on elasmobranch populations in rivers. This will
help to detect any population declines.
For figure &
image - - click here for full PDF
References
Compagno, L.J.V. & T.R. Roberts
(1982). Freshwater
Stingrays (Dasyatidae) of Southeast Asia and
New Guinea, with description of a new species of Himantura and
reports of unidentified species. Environmental Biology of Fishes
7(4): 321–339. https://doi.org/10.1007/BF00005567
Hamilton, F.
(1822). An
Account of the Fishes Found in the River Ganges and its Branches. Archibald
Constable, Edinburgh and Hurst, Robinson, London, 405 pp.
Lucifora, L.O., M.R. de Carvalho, P.M. Kyne & W.T. White (2015). Freshwater sharks and rays. Current
Biology 25(20): R971–R973. https://doi.org/10.1016/j.cub.2015.06.051
Martin, R.A.
(2005). Conservation
of freshwater and euryhaline elasmobranchs: a review. JMBA-Journal of
the Marine Biological Association of the United Kingdom 85(5):
1049–1073.
McEachran, J.D. & M.R. de Carvalho
(2002). Gymnuridae: Butterfly rays, pp. 575–577. In:
Carpenter, K.E. (ed.). The Living Marine Resources of the Western Central
Atlantic. Volume 1: Introduction, Mollusks, Crustaceans, Hagfishes, Sharks,
Batoid fishes and Chimaeras. FAO, Rome, 599 pp.
Mishra, S.S.,
K.C. Gopi, L. Kosygin & P.T. Rajan (2019). Ichthyofauna-Fishes, pp.
539–586. In: Chandra, K., K.C. Gopi, S.S. Mishra & C. Raghunathan (eds.). Faunal
Diversity of Mangrove Ecosystem in India. Zoological Survey of India,
India, 735 pp.
Muktha, M., K.V. Akhilesh, S. Sandhya,
F. Jasmin, M.A. Jishnudev & S.J. Kizhakudan (2016). Re-description of the longtail
butterfly ray, Gymnura poecilura
(Shaw, 1804) (Gymnuridae: Myliobatiformes)
from Bay of Bengal with a neotype designation. Marine Biodiversity 48(2):
1085–1096. https://doi:10.1007/s12526-016-0552-8
Sherman,
C.S., K.V. Akhilesh, A.B. Ali, K.K. Bineesh, D.
Derrick, Dharmadi, D.A. Ebert, Fahmi,
D. Fernando, A.B. Haque, A. Maung,
L. Seyha, D. Tanay, D. Tesfamichael, J.A.T. Utzurrum, T.
Valinassab, V.Q. Vo & R.R. Yuneni
(2021). Gymnura poecilura. The IUCN Red List of Threatened
Species 2021: e.T60117A124440205. https://doi.org/10.2305/IUCN.UK.2021-1.RLTS.T60117A124440205.en
Accessed on 02 March 2022.
Weigmann, S. (2016). Annotated checklist of the
living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a
focus on biogeographical diversity. Journal of Fish Biology 88(3):
837–1037. https://doi.org/10.1111/jfb.12874
Yennawar, P., A. Mohapatra & P.C. Tudu (2017). An account of Ichthyofauna of Digha
coast, West Bengal. Records of the Zoological Survey of India 117(1):
4–21. https://doi.org/10.26515/rzsi/v117/i1/2017/117289
Yokota, L., W.T. White & M.R.
de Carvalho (2016). Butterfly Rays: Family Gymnuridae, pp.
511–521. In: Last, P.R., W.T. White, M.R. de Carvalho, B. Séret,
M.F.W. Stehmann & G.J.P. Naylor (eds.). Rays
of the World. CSIRO Publishing, Australia, 790 pp.