Reproductive biology of Amblypharyngodon mola (Hamilton Buchanan,1822) in pond ecosystem in Assam, North-east India

Abstract

Reproductive biology of Amblypharyngodon mola was studied in Assam during the year 2009-2011. No significant difference was observed in the external morphology between sexes, except during breeding season when the distended and bulging abdomen was vivid in mature female. Gonadosomatic index (GSI) of female A. mola showed three peaks in a year, once during March (15.57), second in June (18.74) and the third during September (17.84). In males, GSI was much lower compared to females; with three peaks in a year, during March (1.422), June (1.49) and September (1.398). Higher values of ova diameter was recorded thrice in a year in March (0.68 mm), June (0.748 mm) and September (0.762 mm), indicating that the spawning season of A. mola commences during these months. Males attained maturity for the first time in the size group 41-45 mm, while females attained first maturity in the size group 46-50 mm. Length at which 50% of the population mature (M50), was estimated as 53 mm in male and 61 mm in female. Females showed dominance over males all throughout the year with average sex ratio of 1: 1.953 (χ2 = 173.069, p< 0.05, N=1660). Absolute fecundity of A. mola varied from 485 (total length 54.4 mm, body weight 1.51 g and ovary weight 0.061 g) to 15786 (total length 91.3 mm, body weight 9.78 g and ovary weight 1.99 g).