Some aspects on the feeding of Gerres oblongus (Cuvier, 1830) dwelling from the Jaffna lagoon

A total of 179 fishes of Gerres oblongus (Cuvier, 1830) ranging in standard length 40 to 169 mm were collected in the morning from four collection sites in the Jaffna lagoon. The stomach contents were assessed qualitatively and quantitatively. The fishes were placed in 19 mm size class intervals and the food analysis were done both by qualitatively and quantitatively. Variation of food with respect to month was also determined. The analysis of gut contents of G. oblongus showed that it is an omnivore and the preference to animal diet is higher than the vegetable matter. The presence of molluscs, soil particles and polychaetes indicated that it is a substratum feeder or feed largely on attached surfaces. Feeding intensity was high during February which has been reflected by the satiation index (8.3) in the same period. At the same time coefficient of condition has been fluctuated in between 2.2-3.7 except in May (4.4) indicated that it has slow growth rate. The mean relative gut length showed a positive increase with the body length. The value for the relationship between the mean relative gut length to body length further confirms that it is omnivorous in feeding habit.