Study on the Effect of Isolation Period in the Aggressive Behavior of Trichogaster fasciata

We tested the effect of isolation period on the aggressiveness of an anabantid fish Trichogaster fasciata. 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 30-32C; pH 6.8-7.1; dissolved oxygen content 5.8-6.4 ppm). After 5, 10, 15 and 20 days the opaque partition was removed and the fish were left to interact for 30 minutes. The aggressive drive was analyzed by different agonistic behavior. 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 fasciata.