(Valenciennes)
1. Distinctive characters of early developmental stages
(a) Eggs and prolarvae (Not collected from the mangroves)
Diameter of egg varies from 1.4 to 1.53 mm with yolky part around 0.8 mm. A single oil globule with about 0.1 mm diameter and at times a small second oil globule is seen. Perivitelline space is large. Prolarva just hatched measure 2.5 mm in length (Ball and Rao, 1990).
(b) Postlarvae (Characters based on 20-22 mm specimens) (After Bensam, 1983)
Sardinella fimbriata 1
Body elongate. Dorsal fin is located above 21st to 30th of pre-anal myomeres and possesses 18 to 19 rays. Anal fin has 18 to 21 rays and caudal fin 28 rays. Pre-anal myomere count varies from 30 to 32 and post-anal myomere count 12 to 13. Pre-anal length is around 20% and predorsal length is around 50% of the total length of the larvae.
(c) Early Juveniles (Based on 45 mm specimen) (after Termvidchakorn, 1989)
Sardinella fimbriata 2
About 15 black spots on the dorsal side of the body, of which half the quantity line the base of dorsal fin and the rest are situated anteriorly before dorsal fin origin. (In adults black dots and blotches are restricted to base of anterior rays of dorsal fin only). Scales start forming and look somewhat irregular. Preventral and postventral scutes count 18 and 12 in numbers respectively.
2. Distinguishing characters of the larvae of related species occurring in the mangroves
(a) Sardinella sp.: Type - I (Based on 15.9 mm Larva)
Sardinella sp. Type I
Body slender and elongate. Maxillary and mandibular bones and pectoral fins well developed. Pectorals occupy about half the depth of larva. Dorsal fin with about 17 soft rays. Ventral fins start developing. Transverse folds in the inner wall of the posterior part of gut are prominent.
3. Distinguishing characters of the larvae of related species occurring in the marine environment
(a) Sardinella longiceps (Based on 18 mm larva) (After Nair, 1959; Kuthalingam, 1960; Lazarus, 1985)
Sardinella longiceps
Body slender and elongate. Mouth is terminal. Pelvic fin has net yet attached its full triangular shape. Dorsal fin is located closer to tail than to the head. Dorsal fin has 16 to 18 soft rays and anal fin 14 to 16 rays. Anal is situated far behind, nearer to caudal. Prepelvic length shorter than postpelvic length. Throat pigmentation well developed on the ventral side of the head around the bottom of eyes and on the anterior and posterior parts of pectoral fin base. Paired prepelvic segments almost like continuous line and postpelvic pigments look like broken line. A total of 47 myomeres are present of which 38 are located in pre-anal region and the rest in post-anal region.
4. Salient biological characteristics
(a) Size
Maximum length 18 cm.
(b) Food and feeding habitats of juveniles and adults in the marine environment
Juveniles predominantly feed on phytoplankton. Adults feed both on phytoplankton and zooplankton.
(c) Reproductive biology
This species spawns during December - March in Gulf of Mannar; October - November in Tuticorin Bay and April - June in Kerala coast. Length at first maturity varied in different locations from 10 cm to 16 cm in Indian waters. (Bal and Rao, 1990; Radhakrishnan, 1964).
5. Salient ecological information
(a) Habitat
Eggs and prolarvae occur only in marine environment. Certain post larval and early juvenile stages occur occasionally in the lower reaches of the mangrove estuaries. Juveniles not yet recorded from south Indian mangroves but reported from mangroves of Singapore and Thailand. (Gomez, 1980; Macintosh, 1991). Adults are principally marine, constituting important pelagic fishery in coastal waters. Indigenous crafts and gill-nets are engaged in coastal environment to tap this seasonally abundant species in Indian region.
(b) Geographic distribution of the species
Throughout Indo West Pacific.
(c) Behaviour
The juveniles and adults of this species exhibit shoaling behaviour for effective feeding of plankton and for escaping from predators. The body shape of this pelagic fish helps to lead a fast swimming nektonic life.