(Bloch)
1. Distinctive characteristics of early developmental stages
(a) Eggs
No information from the mangroves (in general, Silverbellies breed only in a marine environment).
(b) Early juveniles (description based on 19 mm T.L. specimens)
Secutor insidiator 1
The mouth is protruding upwards The body is somewhat elongated and relatively smaller in depth when compared to the S. ruconius. The lateral lines are yet to form fully. Larval preoperculum spines have not yet vanished completely.
2. Salient biological characteristics
(a) Maximum size (James, 1984)
Secutor insidiator – 105 mm
(b) Food habit
In the marine environment, it feeds on small crustaceans (James, 1984).
3. Salient ecological information
In general, leiognathids are demersal fishes. Species of the Leiognathus genus encountered in the mangroves feed both on benthic and planktonic organisms, while the Secutor species seem to feed only on planktonic organisms. The position of the protrusive mouth could be attributed to such feeding types in these juveniles. Among the above mentioned (5 spp.) leiognathids, besides the post-larvae, early juveniles and juveniles, the adults of L. equulus were also recorded from the mangrove waters. Species belonging to all the three genera of the Leiognathidae family occur in the mangroves (Gazza , Leiognathus and Secutor ) of which Leiognathus spp. dominated the other two genera, both in species richness and abundance.
4. Capture fisheries and utilization
Silver bellies constitute the bulk of the demersal fishery resources/trawl fishery/ trash fish fisheries. They are one among the main source of fish for the fish meal industry. The sun-dried fish reach the interior markets and cater for the animal protein needs of the rural poor. The low price of the commodity readily fits the rural economy. Moreover, silver bellies are noted for their medicinal value also – the rich bone content and lean flesh provide calcium and protein nutrition respectively.
Nowadays, the tremendously expanding shrimp farming industry creates a higher demand for trash fish for their fish meal/fish feed plant. As a result, silver-bellies which hitherto served as the major marine protein source to the poor inland rural community may not reach them any longer, but are diverted to the shrimp feed industry to earn foreign exchange at the cost of hampered human resources development.
The fixed stake-nets which are under operation in the mangrove waters of Southeast India indiscriminately catch undersized fish during the northeast monsoon and post- monsoon seasons. Since many species of the Leiognathidae family use mangroves as a nursery ground, safeguarding the nursery environment will improve the marine catch and largely benefit the demersal fishery resources.