Comparative study on the reproductive potential of male morphotypes of <i>Macrobrachium rosenbergii</i> (de Man) in broodstock rearing and larval production

Abstract

Maintenance of appropriate sex ratio is a critical factor in the broodstock development of <i>Macrobrachium rosenbergii</i>. This study is aimed at delineating the reproductive activity of three male morphotypes of M. rosenbergii viz. blue clawed males, (BC), orange clawed males (OC) and small males (SM) and also at optimising the sex ratio in broodstock rearing. Best result yielded in respect of oviposition, hatchability of eggs and survival of larvae in trials conducted with BC males when the ratio was maintained at 1 male: 4 females. On the contrary percentage of oviposition was the least in the case of OC males while SM showed intermediary performance at lower ratios. In trials with BC males, extrusion of eggs could be noticed within 16 days and the period of incubation lasted for 15 to 19 days. When BC males were kept in a sex ratio 1:4, the average prezoea produced and the larval survival worked out to be 62,000/100 g body weight and 35% respectively, this is comparatively superior not only among the various ratios studied in BC male combinations but also among various male morphotypes of M. rosenbergii and therefore recommended for broodstock development under captive conditions. The success achieved in oviposition and viability of egg in various stocking ratios tested has been analysed statistically and discussed.