STUDIES ON SEXUAL DIMORPHISM AND GONADAL DEVELOPMENT OF AN INDEGENEOUS ORNAMENTAL FISH TRICHOGASTER LALIUS

Abstract

The reproductive biology of dwarf gourami Trichogaster lalius was studied during 2007-2008 in the laboratory of West Bengal University of Animal and Fishery Sciences. The study reveals that T. laius is very much sexually dimorphotic. Male dwarf gourami is attractive and more colourful than female. However, this colour is more prominent during breeding season from (March-August) than non breeding season (Sep-Feb). Apart from colour some other secondary sexual characteristics like belly structure, dorsal fin structure and genital opening are studied in this species.This external morphology was found useful for sex identification in this species particularly during breeding season. Hence breeding and non breeding seasons were also determined. Gonadal maturation was studied on the basis of GnSI, TI and OI. The highest Gonadosomatic index (GnSI) in male was found to be 0.583±0.043 while in female the highest value of GnSI was recorded during the month of June (6.218±0.956). The average pre-spawning fecundity of T. lalius was 1024 to 1351 in number for the fish average length and weight of 43.6 mm to 46.33 mm and 1.244 g to1.808 g respectively.