This paper seeks to identify the biomarker response to oxidative stress in Astyanax bimaculatus, a freshwater fish, collected from the Una River and its associated water bodies. The fish were collected using fishing nets at three different points on the river basin, namely Fazenda Piloto (FP), Ipiranga (IP) and Remédios (RM), during the period from December 2013 to March 2014. Physical and chemical analyses of the water at the sample locations indicate that IP and RM possibly have larger concentration of either natural or anthropic pollutants as compared to FP. FP can therefore be considered as the point less impacted by pollutants than other points. Hepatic activity of antioxidant stress enzymes, superoxide dismutase (SOD) and catalase (CAT), were measured in the specimens. The levels of SOD were reduced at RM while they were elevated in fish collected at IP. The CAT levels for the fish at RM and IP were about 148.9% and 202.4% above the values at FP, respectively. These results suggest that antioxidant enzymes could be used as biomarkers to measure oxidative stress caused by pollutants in the Una River Basin.

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Fish spend their whole life cycle in water and receive the influence of its physico-chemical and biological components over time. The activities of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) of aquatic organisms can be altered by pollutants in the water. The aim of this study was to determine whether the activities of LDH and MDH in the gills and liver of Astyanax bimaculatus (lambari do rabo amarelo or Two Spots Astyanax in English), can be used as biomarkers of environmental impact in the Una River (SP) Basin. The lambaris for these studies were collected from three water bodies of this basin designated as p1 (Itaim River), p2 (stream by the road to the Municipality of Remédios) and p3 (lake on the road to the Municipality of Dr. José Luiz Cembranelli). The gills and liver were homogenized and this material was then centrifuged and the supernatant was used for LDH and MDH activity assays using the spectrophotometric method, which determined oxidation rate of NADH. The activities of hepatic LDH and MDH and gill MDH were not statistically different in the lambaris collected at the three sites. In the gill tissue, LDH activity of lambaris from p3 was lower than that from p1.This inhibition of LDH in lambaris from p3, as well as the inferior quality of water there, suggest the occurrence of pollutants in this water. It is concluded that the LDH of lambari gills has potential for use as a biochemical marker of environmental impact in the Una River.