Exchange and aeration of pond water are common practices in semi-intensive freshwater prawn culture, but there is lack of scientifically based information on the results. We evaluated the effects of water flow through the ponds and mechanical aeration in semi-intensive cultures of Macrobrachium amazonicum. A total of 40 juveniles/m 2 were stocked for 4 mo in 12 earthen ponds. Four randomly assigned treatments were applied: no aeration + no water exchange (NN), diurnal aeration + no water exchange (DA), nocturnal aeration + no water exchange (NA), and continuous water flow (CF). Temperature, pH, total suspended solids, and soluble orthophosphate in the water column did not differ among treatments. Dissolved oxygen (DO) concentrations in ponds with nocturnal aeration were significantly higher than in other treatments. The concentration of inorganic nitrogen was significantly higher in the CF treatment, whereas organic nitrogen was higher in treatments NN, DA, and NA. This suggests that primary production is higher in static ponds. Thermal stratification started at 0900 h, and the maximum difference between surface and bottom temperature varied from 1.5 (CF) to 2.8 C (NN). The difference between DO levels in the surface and bottom water of the ponds began to appear at 0800 h and varied from 0.50 (CF) to 5.23 mg/L (NN). Diurnal aeration and high continuous water flow were efficient in disrupting the stratification. No significant difference was found for survival, mean weight, apparent feed conversion rate, and productivity among treatments. Thus, disrupting water stratification, aerating ponds at night, or exchanging the pond water are ineffective in Amazon River prawn farming in semi-intensive systems, at least for stocking densities lower than 40 individuals/m 2 . About 1000 kg of Amazon River prawn can be produced in static ponds with no aeration in approximately 4 mo. This management strategy saves water and energy and reduces production costs.
Trabalhar boas práticas ambientais é muito importante para que ocorra o desenvolvimento de uma responsabilidade e sensibilização com o meio, impulsionando a mudança de valores e comportamentos que busquem soluções para os problemas nos espaços naturais. Este estudo teve como objetivo fazer um diagnóstico sobre os problemas ambientais causados pelo lixo e como estudantes do Ensino Médio percebem os resíduos sólidos produzidos na cidade de Alegre-ES. Para tal a metodologia aplicada teve uma abordagem quali-quantitativa, os métodos de coleta de dados foram observação, questionário estruturados, palestras e campanhas educativas aplicados em uma escola estadual da cidade de Alegre-ES. A averiguação dos dados dos questionários foi feita com a porcentagem da freqüência das respostas obtidas, como ferramenta estatística e análise de conteúdo das palestras e participação dos sujeitos. Com os questionários foi possível expor os problemas do gerenciamento dos resíduos sólidos em Alegre-ES como a não preocupação com o descarte de lixo (90%), desconhecimento dos PEVs (73%), da diferenciação dos materiais recicláveis e do descarte correto dos resíduos perigosos, onde 67% dos respondentes utilizam a coleta regular. Com este estudo, junto as ações de educação ambiental na escola trouxe uma compreensão por parte dos alunos da importância da atuação dos catadores de materiais reutilizáveis e recicláveis, onde estes alunos poderão atuar como disseminadores e sensibilizadores do programa de coleta, contribuindo de forma significativa com a participação da sociedade na reciclagem.
Effluent discharges from aquaculture can reduce water quality in receiving water bodies and that strategies or practices to reduce this are necessary. One possibility is to reduce, or eliminate, water renewal in grow‐out ponds. In this study, we eliminated water renewal in grow‐out ponds associated with the culture of 40 individuals m−2 of Amazon river prawn (Macrobrachium amazonicum). At the end of the culture period it was, however, necessary to drain the pond to harvest the prawns. An experiment was performed in triplicate, in which the water supply characteristics and harvest water characteristics of ponds were evaluated. To reduce these concentrations of total N and P, an aquatic macrophyte (Eichhornia crassipes, water hyacinth) treatment system (CWs) was adopted. The water characteristics in the CWs were evaluated after 1, 3, 7, 14 and 21 days. The water supply of ponds presented the average concentrations of 0.67 ± 0.32 mg L−1 and 17.4 ± 14.7 μg L−1 of total‐N and total‐P respectively. The harvest effluent of ponds had elevated concentrations of different forms of nitrogen (4.44 mg L−1 of total‐N) and phosphorous (100.9 μg L−1 of total‐P). After 1 day of the experiment we found the following reductions in key nutrients in treatment system containing E. crassipes: 90%, 78% and 45% reductions in the concentrations of particulate matter, orthophosphates and nitrates respectively. We noted that after 3 days the nitrates had been reduced by 53%. We concluded that 3 days of this treatment was sufficient for the removal of the additional nutrients that had accumulated in the Amazon river prawn ponds.
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