LAUSR

Abstract The maintenance of quality parameters in fish farming is fundamental to the success of production systems. Ammonia is toxic when present in high concentrations, causing inadequate development, loss of growth, and mortality in fish. Temperature can also cause biochemical and physiological changes in organisms and cause mortality. Curimbata Prochilodus spp. have the potential to be used in fish farming in polycultures in Brazil. However, few studies have been carried out regarding adequate water quality parameters for the production of Curimbata. Thus, the present study determined the lower and upper lethal temperatures (LT50), as well as the lethal concentration (LC50), and sublethal and toxic effects of ammonia on juveniles of Curimbata Prochilodus lineatus through tests of acute exposure for 96 h. In the lethal temperature test, the fish were subjected to treatments of 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, and 40 °C. Temperatures of 10 °C and 40 °C were lethal at 36 and 24 h, respectively. The lower and upper LT50 were 13.8 ± 1.14 and 39.7 ± 1.59 °C at 36 and 12 h, respectively. For the determination of lethal and sublethal concentrations of ammonia (NH3), the fish were subjected to treatments 0.00, 0.75, 1.14, 1.47, 1.82, and 2.21 (mg/L NH3). The LC50 determined for 96 h was 0.62 mg/L and the LC10 for 24 h was 0.93 mg/L. In addition, histopathological evaluation of the gills was adequate to observe the effects of acute ammonia concentrations. Ammonia concentrations above 0.75 mg/L caused irreversible histological changes. The results of the study indicates that the ideal temperature range for breeding Curimbata is 25 °C to 30 °C, since this variation did not influence fish survival. In addition, Curimbata should be grown in water with concentrations below 0.75 mg/L of ammonia.