Sexual Dimorphism and Gonadal Development of Anabas testudineus, Reared in Captive Condition

Sexual dimorphism and gonad cycle of Anabas testudineus reared in captive condition (from January to December 2005) was ascertained based on their external morphological characters, such as, colour of body, black spots seen at the base of the caudal fin, bulgingness of belly and modification of vent as well as development of gonadal materials indicating change in gonad size. In captive condition, both the sexes (male and female) of Anabas exhibited change in sexual characters morphologically particularly during breeding season (June to September). These characters became more prominent during peak breeding season (July and August). Based on modification of colour on the body surface male could not be differentiated from the female during this period. But, it could differentiate mature fishes from immature one in breeding season. Remaining three characters (black spots seen at the base of the caudal fin, bulgingness of belly and modification of vent) are found very much useful for the identification of male and female fish during breeding season. The gonad increased its size (length, weight and volume) during onset of breeding season (June to September), reached to its optimum level on peak breeding season (July and August) and became spent after October.