GROWTH PERFORMANCE OF PENGBA Osteobrama belangeri UNDER VARIED STOCKING DENSITY DURING FINGERLING REARING IN LARGE CONCRETE TANKS

Pengba, Osteobrama belangeri has been declared as the State Fish of Manipur in 2007 due to its vulnerability and importance. Popularity of this fish is increasing in recent years and has created interest among the farmers in plane area. Development of protocol for the fry and fingerling production would facilitate adoption of the species in grow-out systems in the plane. The present experiment was carried out in this context to standardise the ideal stocking density during fingerling production. The study was conducted for 90 days in a set of twelve large concrete tanks (10 m x 5 m x 1 m) grouped into four triplicated treatments. The treatments were stocked with different densities of pengba fry at 20, 30, 40 50 fry/m³ and designated as control, T-1, T-2 and T-3, respectively. Tanks were filled up to 90 cm depth and evaporation loss was compensated at week intervals. Sampling of fish and important water quality parameters (pH, total alkalinity, total hardness, dissolved oxygen, total ammonium nitrogen, nitrite, nitrate and phosphate) were carried out at fortnight intervals.   The survival varied in a range of 71.5-84.0% among the treatments. Both survival and total length reduced significantly with increasing densities from control to T-2 (P<0.05), while no differences were observed between T-2 and T-3 (P>0.05). Similar significant reduction in final body weight as well as specific growth rate (SGR) was also observed with increased densities and in these cases, T-3 was also significantly lower than T-2 (P<0.05) (Table 1). Such results corroborate the inverse relationship between stocking density and growth performance in this species, as also reported in other carps in fingerling rearing system. The gross biomass yield in the two higher densities (40 and 50 /m³), despite their lower survival, were significantly higher than the two lower densities. But the number of fingerlings harvested were 35, 74 and 112% higher in T-1, T-2 and T-3, respectively, over the control. The lowest size obtained in this study even with the highest density (T-4) was of 7.0±1.0 cm and 3.99±0.17 g, which can be considered as an ideal size for grow-out stocking for pengba. Therefore, the present study revealed feasibility of rearing the species from fry to fingerling stage using density up to 50/m³ density.  However, the other lower densities may be used in case of requirement of larger fingerlings accordingly.