Nictemeral Variations for Pacu Caranha, Piaractus mesopotamicus (Holmberg, 1887) Culture in Single - Phase

Studies related to nictemeral variation were executed in a fish growing pond, during all the seasons of the year, collecting data for dissolved oxygen; temperature; pH and electrical conductivity at the feeding channel on pond's surface, bottom and at streamlet bed. The results showed that Autumn was the season which had the lowest values of water temperature, the interval points, during Spring time, had superior average values of temperature when compared to the ones that were observed at external points. The lowest and highest index of pH were during Autumn season. The electrical conductivity didn't show significant differences during Autumn season. The samples obtained from the streamlet had very high significant differences with the samples of fish pond inner part, showing that there was an influence on external environment from the effluent which came from the inner part of the fish pond on limnology variables.