(Valenciennes)
1. Distinctive characters of early developmental stages
(a) Eggs
Arius subrostratus 1; Arius subrostratus 2
The fertilized eggs receive paternal care through incubation in the oro-buccal cavity of the males. The size of the fertilized eggs range from 10 to 12.7 mm in diameter and weigh around 0.9 to 1.1 g each. Atretic eggs not observed along with the normal eggs. Yolk is yellow in colour. The embryo wriggles over the yolk in the egg. The embryo has elongated snont. Authentic identification of egg is mainly based on the parental fish from where the specimens are collected.
(b) Alevins
Not yet collected from the mangrove waterways.
(c) Early juveniles and juveniles
Arius subrostratus 3
Snout relatively longer and pointed (than Arius maculatus ). Maxillary barbels (one pair) reach up to posterior part of eye. No molar-like teeth on the roof of the mouth. Both premaxillary and palatine teeth are villiform. Paired oval shaped palative tooth patches are very small (when compar ing A. maculatus ) and are more than the size of eye (Fischer and Bianchi, 1984).
2. Salient biological characteristics
(a) Maximum size
Up to 395 mm in the mangroves of southeast Indian coast (Jeyaseelan, 1981).
(b) Fecundity
25 to 35 eggs per spawn.
(c) spawning season
Females with ripe gonad occur in the southeast Indian mangroves during January - April and September - October. On the contrary, based on recruitment of early developmental stages, the species seems to breed anytime between May and December in different years according to prevailing hydrobiological and climatological conditions. Detailed studies concerning the reproductive biology of this species are lacking, probably due to sporadic occurrence in the commercial catch.
(d) Food and feeding habits
The early juveniles and adults in the mangrove waterways are feeding principally on benthic fauna. The food items in descending order of importance include: tanaids, gammarids, detritus, polychaetes, mysids, benthic copepods, algal weeds, benthic diatoms and cumaceans (Jeyaseelan, 1981).
3. Salient ecological information
(a) Habitat
Mostly in estuaries, mangroves, tidal rivers and at times in inshore waters less than 20 m. depth. It prefers brackish waters with muddy bottom.
(b) Geographic distribution
From Pakistan, through east and west coasts of India, Indo-Malayan archipelago and up to the Philippines.
(c) Distribution within the mangroves
It occurs in waters with mixo-mesohaline and mixo-polyhaline conditions of salinity in the upper, middle and lower reaches of mangroves. It occurs up to moderate turbid waters (upper limit of 400 g/m^3 seston content).
(d) Behaviour
It is a demersal fish feeding on benthic organisms. It seems to exhibit burrowing behaviours in soft mud of mangrove waterways.
4. Capture fisheries
Often caught in handlines in the middle reaches of mangroves by using gobioids as bait fish.