Maturation and Fecundity of Large Freshwater Prawn Macrobrachium malcolmsonii and Macrobrachium gangeticum in the Ganga River System in India

摘要

The Ganga is the largest perennial river in India. The prawns’ fishery resources are declining in middle stretch of the river Ganga near Patna. The present paper deals with the maturation and fecundity of large size Macrobrachium species like Macrobrachium gangeticum (Bate) and Macrobrachium malcolmsonii ( Edwards) were estimated for the period of two years.? Maturity and fecundity of prawn were evaluated according to the size of prawn, ovary and breeding frequency. The initial stage developing ovaries of M. gangeticum were observed smallandlight yellowish green colour but at stage II to mature gonad of M.? gangeticum were found deep yellow green mass in the carapace, whereas in M. malcolmsonii the developing stage of ovaries was observed large yellowish in colour and matured female gonad were found comparatively in large and deep yellow in the carapace. The gravid females observed long setae at the base of genital aperture and 1- 4 pleopodes in both species. After mating, eggs were transferred by both the female prawn from ovary to brood pouch. Berried prawn M. gangeticum one week old fertilized eggs were looked as yellowish green finally brawn color. Whereas, in M. malcolmsonii , one week fertilized eggs were looked as yellowish-grey then finally changed deep gray. M. gangeticum and M. malcolmsonii female releases of eggs, her ovaries displayed either stage resting or zero characteristics. The species of M. gangeticum possess minimum of 8000 eggs with size 75 mm and the maximum 76,240 eggs with respective size 190 mm, whereas M. malcolmsonii the minimum fecundity observed 8100 eggs with size 75 mm and the maximum fecundity was 81,200 eggs of 190 mm size. The total weights of the eggs per female prawn as well as the mean number of eggs were improved with cumulative length and weight. The breeding frequency of both species were found four times and in first breeding the number of eggs was found slight, but it increased? comparatively in second and third breeding and got decreased? again in fourth breeding.