Stocking Density and Male Morphotypes Formation of Prawn (Macrobrachium rosenbergii) in Probiotic Based Culture System

Abstract

Formation of different morphotypes in male galda in culture ponds is a potential drawback in increase of production; the males with blue claws are bigger than either the orange claw males or SM males. The proportion of these morphotypes in cultured population determines the total production obtained and needs to be looked at what trigger the formation of the different morphotypes. With this aim in view the present study was conducted in an on-going experiment based on the impact of two commercial probiotics -- Zymetin (a food related probiotics) and Super PS (a soil related probiotics) on the production of galda, stocked in three densities. Efforts were made to see if the sex ratio in stocked galda and the doses of probiotics used in the culture treatment had role in the formation of different morphotypes with consequent net result in production obtained; more males with BC claws result in higher production. Three stocking densities tested with the two probiotics in the experiment were - 2 juveniles /m² (T₁), 3 juveniles/m² (T₂) and 4 juveniles /m² (T₃). The sex ratios obtained in the final production were found to be 1.08:1(T₁), 1:1.13 (T₂) and 1.78:1 (T₃) and proportions of BC, OC and SM males were obtained to be 57%,35% and 8% (T₁); 64%, 31% and 5% (T₂) and 25%, 44% and 31% (T₃). The highest proportion of BC male (64%) was obtained from T₂ treatment with consequent highest production of 1158kg/ha followed by 57% BC male with total production of 667.87kg/ha in T₁ and 25% BC male with total production of 787.18kg/ha in T₃. Evidently in T₃ the proportion of SM male (31%) led to increase of production than in production obtained in T₁ with next higher proportion of BC male (57%). The results of the experiment suggested that stocking density of 3 juveniles/m² (5g Zymetin with 20g Mutagen/kg feed) and Super PS (15l liter Super PS with 7.5kg sand /ha/week) was the best in galda production with slightly more females in the production ponds leading to higher proportion of BC males. The findings obtained can be regarded as a preliminary one; further researches can be carried out in this regard in future.