(Forsskål)
1. Distinctive characteristics of early developmental stages
(a) Eggs and larvae
Not yet reported from the mangrove waters.
(b) Early juveniles (description based on 30 mm T.L. specimens)
Epinephelus tauvina 1
The body is brownish with dark vertical oblique bands. The cross bands located posteriorly usually split near the ventral side of the body. Reddish brown spots are normally absent in early juveniles, whereas they are present in juveniles and small adults and again disappear in large adults. The upper part of the spinous dorsal fin has a dark pigmented band. The eye rings are not yet pigmented. The maxillary has yet to reach beyond the border of the eyes (it reaches far beyond the eyes in adults). The operculum has 3 spines and the middle spine is closer to the lower one. Serrations on the upper edge of the preoperculum and spines on the lower angles of the preoperculum are yet to develop. The caudal fin is round. The dorsal fin has 11 spines and 15 rays. The third and last dorsal spines are equal in length. There is no black blotch at the base of the 8th-11th spines of the dorsal fin (certain characteristics encountered in the above described species overlap with E. malabaricus (Fischer and Bianchi, 1984). However, after tracing the growth in natural and mangrove waters from early juveniles to young ones of 34 cm in size in the present study, the above species is accommodated under E. tauvina ).
2. Distinguishing characteristics of early developmental stages in similar species occurring in the mangroves
(a) Early juveniles of Promicrops lanceolatus
The length of the dorsal spines increases gradually from the 1st to the 11th.
(b) Early juveniles of Epinephelus malabaricus
The head and body are covered with small orange spots. Three dark blotches are present on the interoperculum. Oblique and irregular broad dark bars which are distinct and ventrally bifurcated are absent (of the 5 dark bars, the last three are bifurcated ventrally in E. tauvina ). The lower part of the first gill arch has 13-16 gill rakers (17-20 gill rakers in E. tauvina – excluding the rudiments on the anterior region of lower limb).
3. Distinguishing characteristics of early developmental stages in similar species occurring in the adjacent coastal waters
(a) Juveniles of Epinephelus rivulatus
Pectoral fin base has a dark red semi-circular blotch.
4. Salient biological characteristics (after Selvaraj and Rajagopalan, 1973; Anon, 1962; Jeyaseelan, 1981)
The maximum length and weight recorded were 2,130 mm and 265 kg respectively. The maximum weight of the testis and ovary recorded was 15 kg and 17 kg respectively. The calculated fecundity from the largest female so far recorded was over 340 million per individual. Ova diameter studies revealed the occurrence of only one dominant mode of maturing ova, thus supporting the restricted duration of spawning in this species. The spherical and translucent advanced ova with a granulated yolk and without any oil globule measured between 0.37 mm and 0.63 in stage IV ovary. The early developing ova which are small in size (less than 0.075 mm in diameter) occur in greater number in the anterior part of the ovary, whereas the ova in advanced mode are distributed almost equally throughout the ovary. It spawns during the northwest monsoon season, October to December on the Southwest coast of India, and in the post northwest monsoon season, January to February, on the Southeast coast of India. The early juveniles and juveniles enter from the coastal waters to the mangroves during the later part of the post northwest monsoon (March) in the Southeast Indian region. It is a carnivore, feeding on bottom living crustaceans and fishes. In the mangroves, the juveniles prefer shrimps as food.
5. Salient ecological information
Early juveniles and juveniles enter the mangrove waters to obtain rich food. The shallow mangroves also protect these juveniles from predation by other larger carnivores, which are abundant in the clear coastal waters. It is distributed throughout the Indo-Pacific region. In the mangroves, the juveniles often concentrate near to the oyster bed reefs, whereas the adults dwell in a marine environment often associated with coral reefs.
6. Capture fisheries
The adults are caught in the marine environment by long lines, hand lines and bottom trawls (Fischer and Whitehead, 1974). In the mangrove waters, the juveniles are subjected to undersized fishing by drag-nets and cast-nets in a sporadic manner. Larger specimens of over 150 kg in weight were caught from depths of 35-45 m in the Southwest coast of India.
7. Culture fisheries
It is a hardy carnivorous fish with excellent growth potential. Cage culture of this species is attempted in certain Southeast Asian countries. According to March 1993 prices in certain Southeast Asian markets (Singapore), this species fetches around US$20 per kilogram (equivalent to over Rs.600 per kg), whereas in South Indian markets, the sporadic marine catch fetches just less than Rs.50 per kg probably due to lack of awareness among exporters and inconsistent catch, hampering regular marketing and sustained export. If the export value of this produce is not affected much by supply and demand and if the producers are assured a minimum acceptable price by the consumers/importers, there are tremendous prospects for developing the aquaculture production of this species in two phases, as follows: Phase I: the small-scale coastal aquaculture of this species in cages, abandoned shrimp farms and coastal ponds by using wild hatchlings/undersized fish collected from the mangroves and coastal waters, and Phase II: sorting out problems associated with the hatchery production of hatchlings of this gigantic species for large-scale and long-term aquaculture production through intensive cage culture/growout pond culture, etc.