(Bleeker, 1851)
1. Distinctive characters of early developmental stages
(a) Eggs
Not yet recorded from the mangroves.
(b) Larvae (Based on 16 mm T.L. specimen)
Strongylura leiura 1
The upper and lower jaws mildly elongated to form beak-like structure. Lower jaw is slightly longer than upper jaw. Minute teeth are seen on both jaws. Dorsal and anal fins are located at the posterior part of the body. Dorsal fin has 18 rays whereas the anal fin has 24 rays. Dorsal fin originates above 6th anal fin ray. Caudal fin subtruncate/emarginate. Pre-anal fin fold is present. Pectoral fins possess 10 rays. Ventral fin buds emerge mid way between the eye and caudal base. Prominent longitudinal rows of pigments (five to eight in number in different vertical section of the body) are present.
2. Distinguishing characters of early developmental stages in similar species occurring in the mangroves and adjacent coastal waters
(a) Post larvae and early juveniles of Strongylura strongylura
Dorsal fin has 12-15 rays (17-21 in Strongylura leiura ). Anal fin has 15-18 rays (23-25 in S. leiura ). Post larvae at certain advanced stage possess symmetrically arranged spiny dermal projections on the head (Nair, 1952b). Caudal fin round (subtruncate in S. leiura ). Early juveniles, juveniles and adults possess a black spot at base of caudal fin. (No black spot at caudal base in S. leiura ). Less number of vertebrae (59-65) in alizarin prepared advanced post larvae and early juveniles. (Relatively more number of vertebrae - around 88 in S. leiura ).
(b) Post larvae and early juveniles of Tylosurus crocodilus crocodilus
Postlarvae of around 20 mm size show relatively lesser prolongation of upper and lower jaws (when comparing those of S. strongylura and S. leiura ). (After Masurekar, 1967 and Nair, 1952b). Relatively more number of rays (22-24) in dorsal fin (lesser number of dorsal rays - 17-21 in S. leiura ). Relatively lesser number of rays (19-22) in anal fin (relatively more number of anal rays - 23-25 in S. leiura ). Shape of caudal fin round first, then truncate and ultimately forked during the larval development. (Generally sub-truncate/emerginate in S. leiura ). Darkly pigmented small lateral keel is present on the caudal peduncle of early juveniles, juveniles and adults. (No lateral keel in the species of the genus Strongylura ).
3. Salient biological characteristics
Maximum size: 1200 mm in total length (Munro, 1955). Egg mass possesses numerous (thousands of) filamentous eggs. Filaments aid in attachment of eggs with seaweeds/algalweeds to avoid drifting by currents. This species is a carnivore feeding mainly on fishes and crustaceans.
4. Salient ecological information
This species inhabits coastal waters, estuaries and brackish water mangroves. Adults are never reported from mangroves (though another counterpart, S. strongylura is reported to breed in brackish water/estuaries (Anon, 1962)).
5. Geographic distribution
East coast of Africa, the Gulf coast, Pakistan, India, Sri Lanka, South East Asia, Papua New Guinea, Australia and the Philippines.
6. Fishing ground (After Collette, 1984a)
West coast of India including Veraval, Karwar and Cochin.