Growth performance of pengba, Osteobrama belangeri (Valenciennes, 1844) and water quality changes during fingerling rearing with varied stocking density in large outdoor concrete tanks

Abstract

Fingerling rearing of pengba, Osteobrama belangeri, was conducted at varied densi-ties for 90 days in 12 outdoor concrete tanks (10 m × 5 m × 1 m). The tanks, grouped into four triplicated treatments, were stocked with fry at 20, 30, 40 and 50 fry m-3; and designated as control, T-1, T-2 and T-3 respectively. Tanks were filled up to 90 cm depth. Evaporation loss compensated fortnightly. Fish sampling and monitoring of water quality parameters done at fortnight intervals. Survival varied between 71.5% and 84.0% in treatments. Both survival and total length significantly reduced with increasing densities from control to T-2 (p < .05), while no differences were observed between T-2 and T-3 (p > .05). Similarly, significant reductions in final body weight and specific growth rate were observed with increased densities and these values further reduced in T-3 than T-2 (p < .05). Such results corroborated the inverse relationship between stocking density and growth. Gross biomass yields in two higher densities (T-2 and T-3), despite their lower survivals, were significantly higher than the two lower densities. The numbers of fingerlings harvested were 35, 74 and 112% higher than the control in T-1, T-2 and T-3 respectively. The lowest size obtained even at the highest density (T-3) was of 7.0 ± 1.0 cm and 3.99 ± 0.17 g, which can be considered as ideal grow-out stocking size of pengba. Therefore, the study showed feasibility of stocking up to 50 fry m-3 for rearing from fry to fingerling stage. However, the other lower densities may be used in case of requirement of larger fingerlings.