Reproductive biology of Macrobrachium lar in Andaman Islands

Abstract

Reproductive biology of the Monkey river prawn (Macrobrachium lar) was studied in the Rangat river, Andaman Islands, during 2007 to 2009, with the aim of determining the male: female ratio, maturity cycle, spawning seasons and the fecundity in those ecosystems. During 18 months period, 2078 individuals were collected, with a male: female ratio (M/F) of 1: 2.84. Total number of individuals caught per month ranged 65-172. Males were generally larger than females. Percentage occurrence of reproducing and non-reproducing females, ovigerous females, seasonal occurrence of maturity stages, and maturity indices (GSI and HSI) exhibited that M. lar breeds twice in a year with two breeding peaks (June and November) every year. Highest reproduction indices (GSI) in female were observed in November (4.0 ± 0.07), December (3.88 ± 0.28), May (3.63 ± 0.08), and June (3.88 ± 0.16). In both the sexes, HSI showed inversely proportional relationships with GSI. With respect to average fecundity (F) by length classes, the lowest and highest number of eggs observed was 3090 and 8177, respectively. As for fecundity by weight classes, the lowest number of eggs observed was 4069 and the highest, 8543. Overall mean fecundity irrespective of the length and weight classes was 5402 (± 772.35) eggs per female. Diameter of non-eyed and eyed eggs ranged between 0.32 mm to 0.50 mm and 0.52 mm to 0.68 mm respectively.