Organic and conventional agriculture: Conventional rice farming causes biochemical changes in Astyanax lacustris

World food production is directly related to human population growth. Chemicals are constantly applied to pest control in crops to increase productivity. Therefore, sustainable alternatives are needed to reduce environmental impacts. The biochemical responses in liver and muscle of Astyanax lacustris collected in different rice planting systems were analysed. Ten fish were collected in organic rice cultivation systems and conventional as well as water and sediment for pesticide analysis. In water from conventional system, bentazon (56.1 μg L^-1), fipronil (0.226 μg L^-1) and propoxur (0.141 μg L^-1) were found, while azoxystrobin and quinclorac were below the limit of quantification (LOQ). There were no pesticides in the sediment from the conventional system. In the water of the organic system, only propoxur (below the LOQ) was registered. Metalaxil (0.025 μg kg^-1) were verified in the sediment, while diphenoconazole, dinoxifene and tebuconazole were below the LOQ. The presence of these pesticides in crops with an organic production system may be related to proximity to crops to conventional production systems. Besides this, the amount is very low as compared with conventional system. Muscle glycogen, protein and amino acid levels were higher in fish collected in organic ponds. Lactate and ammonia levels were higher in conventional cultures. Lipids and proteins had greater oxidative damage in both tissues in the conventional system. Although pesticides were detected in organic sediments, the parameters of metabolic and oxidative damage were probably related by exposure to higher concentrations of pesticide in the water or by the lower oxygen content of conventional systems. However, fish mortality was not observed during collections. Despite being an anthropic environment, areas of organic cultivation seem to present better conditions for the survival of A. lacustris.