Abstract
To develop quality broodstock of freshwater prawn Macrobrachium rosenbergii in captive condition, experiments were carried out up to F2 generations at Southern Agro Fisheries and Allied Limited (SAFAL), Subarnachar, Noakhali. Initially 1080 prawn juveniles were collected from the Bulla river, Noakhali and 180 juveniles were stocked in each of 6 ponds (600 m2 each) at a stocking density of 0.3/m2 maintaining 1:1 male-female ratio. The juveniles were reared with three different feeds named as Mega feed (37% protein), Quality feed (26% protein) and Own formulated feed (32% protein) under three treatments designated as MF, QF and OF respectively having two replicates each. Berried females of OF were designated as 'Own developed broods' (OB) and were transferred to Upakul Freshwater Prawn Hatchery (UFWPH), Sonapur, Noakhali for assessing breeding performances along with two other female broodstocks of the Halda river (HB) and Gher (GB). F1 PL produced from these three broodstocks were reared for 56 days in the ponds used earlier at a stocking density of 25/m2 supplemented with nursery CP feed under three treatments designated as F1 PL of HB, F1 PL of OB and F1 PL of GB. Similarly F2 PL produced from F1 broods of Halda and Own developed were reared under the treatments designated as 'F2 PL of HB' and 'F2 PL of OB'. F2 PL of GB could not be produced due to outbreak of disease causing total mortality of F2 larvae of GB. Juveniles of F1 and F2 generations produced from nursery phases were reared for 240 days in the same ponds at a stocking density of 1/m2 supplemented with Own formulated feed. Female broods of F1 and F2 generations produced from grow-out phase were used in UFWPH under the treatments designated as F1HB'; 'FOB'; F1GB and 'F2HB'; 'F2OB'. In feeding experiment (Experiment 01), the highest growth was observed in MF (SGR 0.4 %g/day) but OF showed early gonadal maturation. The highest survival rate and net production were found in OF (49.5% and 133.5 kg/ha respectively) followed by MF (37.8% and 114.2 kg/ha respectively) and QF (34.5% and 83.6 kg/ha respectively). In nursery phase, PL to juvenile conversion rate of HB and OB in Fi generations (64.9% and 60.9% respectively) were not significantly different (P>0.05) from each other and were higher than those of GB (35.3%). The PL to juvenile conversion rate of HB and OB in F2 generations (86% and 71% respectively) also showed no significant difference (P>0.05) but were higher than those of their F1 generations. In grow-out phase, the growth of females in Fi generations in terms of weight gain and SGR was the best in OB (1978.0% and 0.6%g/d respectively). Survival and active female broods in HB (72% and 48%) and OB (69.3% and 40%) in Fi generation were higher than those of GB (35.3% and 12% respectively). In F2 generation, growth in terms of weight gain and SGR in females of HB (1295.2% and 0.5% g/d respectively) and OB (1300.3% and 0.5% g/d) were lower than those of their Fi generation. In F2 generation survival rates of HB (68.2%) and OB (67.7%) were similar to those of their F1 generations but average weight of berried females decreased from F1 to F2 generations in HB (67.9 g to 51.4 g) and OB (69.9 g to 51.5 g). In breeding trial, fecundity of HB and OB was not significantly different (92,418 and 92,784 respectively) and in their F1 generations (77,867 and 69,244 respectively) but were higher than those of GB and F1GB (15,908 and 30,310 respectively). In F2 generation fecundity of broods originated from HB and OB dramatically decreased to 29,006 and 31,398 respectively. Hatching rate of eggs in HB, F1HB and F2HB increased gradually (47 to 50 and 70% respectively). Similar was the case in OB, F1OB and F2OB (43 to 50 and 68% respectively). PL conversion rates also gradually increased in HB, F1HB and F2HB (23.1 to 43.7 and 40.8% respectively) and in OB, FOB and FOB (20.1 to 40.3 and 43.5% respectively). Though egg hatching rate and PL conversion rate of HB and OB increased in the following generations, egg production capacity was seriously affected in F2 broods. The results revealed that F1 generations of HB and OB of M. rosenbergii reared in captivity with proper diet had the best growth and breeding performances. The study suggested that quality broodstock of M. rosenbergii can be developed in ponds/captivity by rearing PL or juveniles collected from wild sources with formulated feed containing 32% protein and proper water management.