DOI: 10.36347/sajb.2013.v01i04.001

Pages: 104-107

Aggression is a key component of the behavioral repertoire of animals that impacts on their Darwinian fitness. Anabantid fishes are excellent model for comparative ethological studies for several physiological and behavioral reasons. We tested the effect of isolation period on the aggressiveness of an anabantid fish Trichogaster lalius. A pair of male fishes were placed in an aquarium (12 ̋x 9 ̋x 9 ̋), isolated by a removable opaque partition. The fishes were of comparable size and weight (varying not more than 10 % in weight). Chemical conditions of all aquaria were similar (temperature 30-32oC; pH 6.8-7.1; dissolved oxygen content 5.5-6.2 ppm). After 5, 10, 15 and 20 days the opaque partition was removed and the fishes were left to interact for 30 minutes. The aggressive drive was analyzed by different agonistic display. Total duration, latency of orientation and mouth biting increased with the increased period of isolation. But lateral spread, circling, chasing and air gulping decreased with the increased period of isolation. This study showed that long-term social isolation though increased total duration of aggressiveness but except mouth biting all other aggressive motor patterns decreased in Trichogaster lalius.