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Fertilization of aquaculture ponds has been pointed out as an efficient practice to improve fish feed conversion and growth performance. In this way, the present study aimed to assess the effect of pond fertilization on the growth performance, body composition, and water quality of juvenile pirarucu Arapaima gigas reared in earthen ponds (600 m²) during the grow-out phase. Two fertilized and two non-fertilized ponds were stocked with 208 juvenile pirarucus (19.9 ± 3.6 g and 15.0 ± 0.9 cm) and reared for 100 days. All four ponds were limed before the study. Ponds were fertilized before fish were stocked and weekly until the end of the experiment, and fish offered feed until apparent satiation. Pirarucu reared in fertilized ponds presented higher final weight (20%) and biomass (19%), further to lower feed intake and feed conversion rate (1.31) than fish reared in non-fertilized ponds (1.61). Pond fertilization did not affect the fish coefficient of variation, which was reduced over the culture cycle. The body composition of fish reared in fertilized ponds presented higher water content, protein, and energy retention rates and lowered crude fat and energy. Fertilized ponds presented lower transparency levels and higher pH from the 50th day of culture, whereas ammonia concentration was higher in the fertilized ponds in the first 25 days. Therefore, pond fertilization is a recommended practice for pirarucu during the grow-out phase. [ABSTRACT FROM AUTHOR]

The effects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low-cost cage-cum-pond integrated system for production of Oreochromis niloticus (L.). Hand-sexed male fingerlings averaging 19±0.39 and 32±0.69 g were stocked in cages and open ponds at 150 fish cage−1 and 2 fish m−2 respectively. Fish were cultured for 114 days in five triplicate treatments. Cages were installed into ponds and caged fish were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day−1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged fish, which were fed 6% BWD for the first 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open-pond fish fed. Feeding rate and pond fertilization significantly ( P<0.05) affected fish growth, profitability and water quality among treatments. Fish growth, feed utilization, fish yield, water quality and profits were significantly ( P<0.05) better in T3 than the other treatments. It was concluded that fish production and economic returns were optimized at 6% BWD in fertilized ponds. [ABSTRACT FROM AUTHOR]

The effects of open-water and caged fish density on growth, feed utilization, water quality and profitability were investigated to assess the feasibility of a small-scale rotational system for production of Oreochromis niloticus (L.) in fertilized ponds. Hand-sexed male fingerlings averaging 18.6 and 29.9 g were stocked in open water and cages, respectively in four treatments with open-pond:caged tilapia ratios of 300:0 (control), 150:150 (L), 300:150 (H1) and 300:300 (H2). The ponds in L and H1 contained one cage, two cages in H2, and the control ponds had no cages. Each cage contained 150 fish, which were fed daily at 1.5% body weight for 125 days. All fish in the open water except the control fish were not fed. Growth of open water tilapia was significantly ( P<0.05) higher in L than in control. Feed utilization, dawn DO and economic returns were significantly better ( P<0.05) in caged than control ponds. Growth of tilapia in L was significantly lower ( P<0.05) in cages than in open water. Fingerling production was significantly lower ( P<0.05) in L than in other treatments. In conclusion, cage-cum-open-pond integrated treatment (L) was optimal for O. niloticus production in fertilized ponds. However, the system could not rotate and needed further fine-tuning to rotate. [ABSTRACT FROM AUTHOR]