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Fish culture and irrigation reservoir; oxygen dynamics; primary production
Abstract:
Common carp (Cyprinus carpio ) grew at about 6 g/day and tilapia (Oreochromis ) at 3.7 g/day during the intensive growing period (May-August). Significant differences between months, hours and depths of temperature, oxygen concentration and saturation, chlorophyll and total suspended solids occurred. Heat transport from surface to bottom occurs during all the day hours, and DO and chlorophyll transport in the same direction by the end of the day. Oxygen production compensated oxygen consumption at three times the Secchi disk depth. Compensation depth in the reservoir (generally about 1 m depth) was higher than the reported 40-70 cm in shallow fish ponds. Gross primary production in surface waters ranged from 2.4 to 3.3 mg DO/l/hour, lower than in shallow fish ponds in the same area. Since the euphotic layer is thicker in the reservoir, gross primary production per unit area results the same in both systems (between 1.3 and 1.9 g DO/m super(2)/h).
