(Cuvier, 1829)
1. Distinctive characteristics of early developmental stages
(a) Eggs and Larvae
No information from the mangroves.
(b) Early juveniles: (Based on 45 mm T.L. specimens)
Sphyraena jello 1
The body is elongated and cylindrical. The head is proportionately larger in early juveniles than in adults.
The snout is pointed, the lower jaw longer than the upper jaw, and the upper jaw does not reach the level of eye. The angle of the preoperculum is round. The pectoral fin is proportionately larger at this stage than in adults. In the first spinous dorsal fin, the first spine is the shortest (in adults, the last spine is the shortest). The posterior edge of the forked caudal fin is ‘v’ shaped ( ‘w’ shaped in adults). Vertical bars (around 6 in number) of assorted size and shape are distributed throughout the entire length of the body of which certain bars occupy the entire depth of the body (in adults up to 20 vertical dark patterns of serpentine bars are present which extend a little below the lateral line). There are no inky blotches between the anal base and lateral line.
2. Distinguishing characteristics of early developmental stages in similar species occurring in the mangrove environment
(a) Early juveniles and juveniles of S. barracuda
The maxilla reaches up to the level of eye (not so in S. jello ). Vertical bars do not reach below the lateral line (vertical bars reach a little below the lateral fine in S. jello ). S. barracuda is a well recognized species which uses the mangroves as a nursery ground (vide Fischer and Bianchi, 1984 for further details).
(b) Juveniles of S. obtusata
The preoperculum angle is rectangular in shape (round in the case of S. jello ). Vertical bars are absent (vertical bars present in S. jello ). Early juveniles of S. obtusata have not been reported from the mangroves, whilst the juveniles ranging from 77-160 mm were recorded from the mangroves of Southeast India (Jeyaseelan, 1981).
3. Salient biological characteristics
This species grows to a maximum size of 1500 mm in length in the marine environment. It is a carnivore predator on fish and squids in the marine environment. In mangrove waters, the juveniles feed on small fish and shrimps.
4. Salient ecological and evolution related information
It is an epipelagic species, actively preying on fish and other organisms during day time. The body shape aids faster movement in the water to capture the prey organisms. The mouth and teeth patterns help to capture the prey effectively. Old fish are solitary, while the young ones form small schools. This species inhabits reefs and shallow banks, while the juveniles use mangroves, brackish waters and backwaters as a nursery ground.
Among the Mugiliformes order, three families have evolved with distinct feeding behaviour. They include Atherinidae-plankton feeding fishes; Mugilidae – principally detritus feeders and sphyraenidae – with carnivorous feeding behaviour. S. jello belongs to Sphyraenidae which is a voracious carnivore.
5. Capture fisheries and utilization
In the marine environment, it is caught by trolling by traditional and sport fishermen. It is also captured by trawling – but in smaller numbers, and marketed in fresh, dried and salted conditions. Ciguatera poisoning reported from this species is attributable to unreliable identification (poisoning has been reported from an allied species – S. barracuda which has vertical bands similar to S. jello ) (Fischer and Bianchi, 1984).