Resumo

TORRES-MESA, Ana C; TOVAR-BOHORQUEZ, Mario O; HURTADO-GIRALDO, Hernán  e  GOMEZ-RAMIREZ, Edwin. Total ammonia nitrogen excretion at different Cyprinus carpio sowing densities in aboratory conditions. Orinoquia [online]. 2015, vol.19, n.1, pp.19-26. ISSN 0121-3709.

Total ammonia-nitrogen (TAN) excretion from aquaculture systems is determined by several biological and physicochemical parameters, such as sowing density. If TAN is not suitably controlled, food consumption and growth will become reduced, eventually leading to death. The relationship between sowing density and TAN excretion rate must thus be defined for establishing suitable conditions for fish growth. The common carp (Cyprinus carpio) was used as experimental model in this work. Two treatments were evaluated (T1 involved 30 individuals and T2 60 individuals per experimental unit in 40 l aquariums) with three repeats; this involved measuring weight and total and standard length at the start of the experiment and every 14 days thereafter. Weekly follow-up was made regarding water pH, temperature and carbonate and overall hardness. Samples were taken every four days for recording TAN and dissolved oxygen. The TAN excretion rate was calculated for 14 day periods. TAN excretion rate result on day 14 for T1 was 0.69±0.009 µg g^-1 hour^-1 with 18.33±0.13 g biomass and 0.40±0.02 µg g^-1 hour^-1 with 34.66±0.33 g biomass for T2; on day 28 T1 gave 0.53±0.02 µg g^-1 hour^-1 with 24.8±0.3 g biomass and 0.28±0.03 µg g^-1 hour^-1 and 48.99±2.58 g biomass for T2; on day 42 T1 = 0.47±0.02 µg g^-1 hour^-1 with 32.3±1.7 g biomass and T2 = 0.26±0.02 µg g^-1 hour^-1 with 69.81±7.04 g biomass. Such results led to concluding that the total ammonia excretion per gram rate decreased with higher sowing density.

Palavras-chave : Water quality; osmoregulation; biomass; excretion mechanism.

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