Introduction
Fishes of the family Exocoetidae are commonly known as flying fishes due to the presence of elongated pectoral fins, sometimes pelvic fins and larger lower lobe of the caudal fin in individuals, which provide a wide range of gliding and aerial escapes from predators (Breder, Reference Breder1930; Lewallen, Reference Lewallen2012). Exocoetidae is a monophyletic group under the order Beloniformes, that represents an epipelagic fish community that inhabits mainly in neritic and oceanic waters of tropical and subtropical seas throughout the world (Barman and Mishra, Reference Barman and Mishra2006; Lewallen et al., Reference Lewallen, van Wijnen, Bonin and Lovejoy2018). Members of this family comprise of 80 species under seven genera (Fricke et al., Reference Fricke, Eschmeyer and Fong2024a). From Indian waters, a total of 24 species of flying fish are enlisted in six genera (Jayakumar et al., Reference Jayakumar, Shakhovskoy, Prasoon, Kathirvelpandian, Ajith and Lal2019).
During the local survey around the Petuaghat fishing harbour (21°47′4.05″ N; 87°52′5.99″ E) of West Bengal (north-east coast of India), the authors collected two flying fishes and identified them as Cheilopogon arcticeps (Günther, Reference Günther1866), which was previously reported only from the Western Pacific Ocean (Parin, Reference Parin1999; Froese and Pauly, Reference Froese and Pauly2024; Fricke et al., Reference Fricke, Eschmeyer and Van der Laan2024b). The present manuscript provides material evidence of the species for the first time from the Indian Ocean along the Bay of Bengal as well as Indian waters with a westward extension of its distributional range.
Materials and methods
Two specimens of an interesting flying fish (Figure 1) were collected from the Petuaghat fishing harbour of West Bengal, India on 12 October 2019 during the local survey of the West Bengal coast. Measurements of the specimens were done by the aid of digital callipers with an accuracy of 0.1 mm. Photographs were taken with a Nikon Z30 digital camera. Digital radiography was used to capture an X-ray image of the fish's vertebrae, allowing for precise counting and analysis. Species identifications were done following Parin (Reference Parin1999) and Barman and Mishra (Reference Barman and Mishra2006). The species was found to be C. arcticeps (Günther, Reference Günther1866) and the specimens of it were deposited in the museum of the Estuarine Biology Regional Centre, Zoological Survey of India, Gopalpur-on-Sea, Odisha in 10% formaldehyde solution. Abbreviations used: D – dorsal fin; A – anal fin; P – pectoral fin; V – pelvic fin; LL – lateral line scales; SL – standard length; and GR – gill rakers.
Figure 1. Cheilopogon arcticeps (Günther, Reference Günther1866) – F-13087.
Results
Diagnostic specific characters along with morphological characters of the specimens are expressed hereunder.
Characters
D 11–12; A 8–9; P 15; V 6; GR 17; LL 49. Body cylindrical and elongated covered with large cycloid scales. Head short, 4.28–4.49 of SL and scaleless; scales present on dorsal surface starting behind the supraoccipital process; snout short and more or less pointed, 3.82–4.05 in HL. Eye larger than snout, its diameter 2.85–3.20 in HL. Interorbital space flat, 2.80–2.86 in HL. Small, non-protrusible mouth with lower jaw slightly longer than upper jaw; numerous villiform teeth present on jaws. Palatine teeth are absent. Dorsal fin is moderately low with the longest ray about 10.5 times in standard length. Predorsal length 1.45–1.46 of SL; origin of anal fin 4–5 rays behind origin of dorsal fin, preanal length 1.42–1.48 of SL; pectoral fins very long, its length 1.63–1.64 of SL, reaching till the end of anal fin base; only the first pectoral-fin rays unbranched; pelvic fins long, its length 3.4–3.6 in SL, reaching well beyond anal-fin origin, inserted nearer to anal-fin origin than to pectoral-fin insertion, but nearer to head than to lower caudal fin origin; caudal fin forked, lower lobe much longer than upper lobe; spine absent in fins. Lateral line scales 36–37, predorsal scales 27–28, prepelvic scales 17–19, transverse scale rows 7–8 present between dorsal fin origin and lateral line scales; vertebrae: 43 (Fig. 2); gill rakers on lower limb of first gill arch 17. Barbels absent. Details of morphometric measurement and meristic count are represented in Table 1.
Figure 2. Vertebrae of Cheilopogon arcticeps (Günther, Reference Günther1866).
Table 1. Morphometric and meristic characters of Cheilopogon arcticeps (Günther, Reference Günther1866) collected during the present study
Colour
Pectoral fins without any dark spot; fin membrane between 2 and 7 pectoral fin rays dark, other rays white. No black blotch on the dorsal fin.
Distribution
Previously, this species was recorded along the coasts of southern China, Indonesia, New Guinea, Solomon Islands, Thailand and Vietnam (Parin, Reference Parin1999), the Philippines (Froese and Pauly, Reference Froese and Pauly2024) and Japan (Fricke et al., Reference Fricke, Eschmeyer and Fong2024a). In this present paper, C. arcticeps (Günther, Reference Günther1866) has been reported as the first distributional record from the Bay of Bengal along the West Bengal coast of India with a range extension from the Western Pacific Ocean to the Eastern Indian Ocean.
Discussions
The genus Cheilopogon Lowe, 1841 stands as the most species-rich and morphologically diverse group within flying fishes, comprising 33 confirmed species till date (Fricke et al., Reference Fricke, Eschmeyer and Van der Laan2024b). Cheilopogon differs from other genera of the family in having a dorsal fin clearly anterior to the anal fin origin, a little longer lower jaw, and juveniles with paired barbels (Parin, Reference Parin1999; Barman and Mishra, Reference Barman and Mishra2006). Cheilopogon arcticeps is known to have a distribution in the Western Pacific Ocean (Parin, Reference Parin1999; Froese and Pauly, Reference Froese and Pauly2024; Fricke et al., Reference Fricke, Eschmeyer and Fong2024a). This species is pelagic in nearshore and neritic surface waters which never spread to open sea (Parin, Reference Parin1999). Jayakumar et al. (Reference Jayakumar, Shakhovskoy, Prasoon, Kathirvelpandian, Ajith and Lal2019) erroneously reported the presence of this species in the waters surrounding the Nicobar and Andaman Islands, referencing the work of Parin (Reference Parin1999). However, Parin's study (Reference Parin1999) did not explicitly confirm the occurrence of C. arcticeps in these waters. Further, Shakhovskoy and Parin, (Reference Shakhovskoy and Parin2019) clearly mentioned that this species is absent in the Western Indian Ocean. Satapoomin (Reference Satapoomin2011) listed C. arcticeps from south-western Thailand, the Andaman Sea with the distribution category as west Pacific. Possibly this was the western limit of this species, it has not yet been recorded from the Nicobar or Andaman waters. Hence, the present report extends its westward range to the northern Bay of Bengal of Indian coast.
The original description (Parin, Reference Parin1961) of C. arcticeps seems insufficient as the brief description mostly contains juvenile characters. Juveniles of C. arcticeps have two short chin barbels, pale proximally and dark distally (Shakhovskoy and Parin, Reference Shakhovskoy and Parin2019). However, based on Parin (Reference Parin1999) it is identified for having following combination of characters: ‘low dorsal fin, rays more than 10 times in SL; lower jaw little longer than the upper; absence of palatine teeth; pelvic fin insertion nearer to head than to lower lobe of caudal fin; no dark spots on pectoral fin; 8 or 9 anal fin rays; predorsal scales 27 or 28; lateral transverse scales between D origin and LL 7 or 8’.
The present study reports two examples of adult C. arcticeps, indicating its occurrence is not restricted to Western Pacific Ocean only. The present report from the West Bengal coast of India extends its range to Bay of Bengal as well as Indian Ocean. More extensive studies are needed for understanding the regional distribution, relative abundance, systematics and biogeography of flying fishes around Indian Ocean.
Acknowledgements
We thank Dr Dhriti Banerjee, Director, Zoological Survey of India for providing working facilities. We thank the reviewers for the critical review and the handling Editor for the completion of the review process in a quick time.
Author contributions
Collection and identification: D. R., T. K. and S. S. M. Data analysis: D. R. and S. R. Manuscript preparation: D. R. and A. M. Manuscript editing and verification: A. M. and S. S. M.
Competing interest
None.
Ethical standards
The IUCN Red List, the Convention on International Trade in Endangered Species of Wild Fauna, and the Government of India's Wildlife Protection Act do not list the fish specimens utilized in the study. The specimens were collected in dead condition from the fish landing Centre.
