Abstract
An experiment to observe the effect of different levels of mineral phosphorus with and without nitrogen on the dry
weight of planktonic biomass, increase in fish production and biomass conversion efficiencies was conducted at
Fisheries Research Farms, University of Agriculture, Faisalabad in nine earthen ponds. The area under each
pond was 30 x 16 x 2m. Fingerlings of Hypophthalmichthys molitrix, Labeo rohita and Cyprinus carpio were
collected from the Govt. Fish Seed Hatchery, Faisalabad and stocked in the experimental ponds with a stocking
density of 251 each pond. The experimental pond 0 served as the control without any additives, whereas the
pond 1, 2, 3, and 4 received mineral fertilizer (triple superphosphate, 46% P2O5) at the rate of 0.06, 0.09, 0.12 and
0.15 percent of wet fish body weight per day, while pond 5, 6, 7 and 8 received phosphorus in the same
ascending order along with nitrogen (urea, 46%) at the constant rate of 0.12% N, of wet fish body weight daily and
the study continued for twelve months. Fortnightly observations on an increase in fish production, dry weight of
planktonic biomass and biomass conversion efficiency ratios were made. The overall range of increase in fish
biomass in 24 fortnights under T1, T2, T3, T4, T5, T6, T7, T8 and T0, were in the tune of 1.64-27.42, 1.65-20.93,
1.92-44.59, 1.46-43.70, 1.48-69.63, 2.65-32.24, 0.89-32.09, 1.45-41.46 and 0.59-3.31 g m-3; while the dry weight
of planktonic biomass throughout the experimental period ranged from 43 to 176, 48 to 215, 42 to 220, 63 to 320,
49 to 327, 58 to 234, 48 to 210, 58 to 234 and 8 to 58 g m-3, respectively. The biomass conversion efficiency
ratios ranged from 0.01 to 0.25, 0.02 to 0.24, 0.02 to 0.55, 0.01 to 0.26, 0.02 to 0.44, 0.02 to 0.30, 0.02 to 0.18,
0.01 to 0.32 and 0.02 to 0.25 in T1, T2, T3, T4, T5, T6, T7, T8 and T0, respectively. Treatment pond, T5 which was
fertilized with 0.06 percent phosphorus plus 0.12 percent nitrogen remained the best treatment in which maximum
net fish production of 462.51 kg pond-1 yr-1 was procured.
