I got this two images of a Eagle Ray for photo ID. The person who sent me this images gave me the following information: off Marve, Malad-Mumbai, size is around 20-22 inches, in a fisherman's net, tail cut-off, he assumed it could be a species of Aetomylaeus.
I think it is Aetobatus flagellum (BLOCH & SCHNEIDER, 1801) because
-the pectoral fin is seperate from the rostral lobe,
-the pectoral fin joining the head at level of the eye
-the snouth with a single convex rostral lobe
-broad and short disc
-dorsal surface brownish to greenish without any markings
-large spiracles
What is your opinion?
It certainly looks like to be Aetobatus flagellum. The site of collection falls within the natural habitat and migratory paths of the longheaded eagle ray and is endangered but the colour of the dorsal surface, greenish grey with brownish patches, is more akin to A. narutobiei which happens to be a NW Pacific species.
Following White et al. 2013 the two species can distinguish based on the following characters. I agree with you that it could be A. narutobiei too, because the following characters couldn't correctly identified.
1. larger maximum size (1500 mm DW in A. narutobiei vs. 900 mm DW in A. flagellum)
2. larger size at maturity (males become mature between 759 and 800 mm DW vs. between 446 and 543 mm DW)
3. larger size at birth (free swimming at 352 vs. 233 mm DW)
4. rostral lobe of adult males narrowly parabolic and tapering evenly to tip (vs. not tapering posteriorly then abruptly tapering to tip near apex)
5. possibly greater number of tooth series (upper jaw 13 vs. 6
6. lower jaw 18 vs. 13 [NB based on only a single jaw in each species])
7. more metapterygial pectoral-fin rays (55–58 vs. 48–54) and total, excluding propterygial rays anterior to eyes, pectoral-fin rays (100– 104 vs. 89–96)
8. more pelvic-fin rays (1+17–18 vs. 1+14–16)
9. dorsal fin less raked back with posterior margin almost perpendicular to tail or slanting slightly posteroventrally from apex, its anterior margin length 4.9–5.8% DW (vs. more raked back with posterior margin mostly slanting slightly anteroventrally from apex, anterior margin length 5.6–7.9% DW)
10. slightly greater width across pelvicfin bases, i.e. 12.1–15.7 vs. 9.7–12.8% DW
11. lower half of orbit around eye mostly whitish, sometimes greenish to brownish ventrally but whitish between this and the darker upper margin (vs. orbit with brownish margin around entire eye)
12. Aetobatus narutobiei also appears to have a much longer lower tooth band than A. flagellum, but this is based on only a single specimen of each species and thus intraspecific differences cannot be adequately ascertained.
A close up of the snout with dentition and size scale could have been of more help. The whole specimen would have eased the process of identification also. The tail being severed prior to the photograph did not help either.
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