| Summary: | Background. Ventilation volume is a parameter used mainly for determining oxygen consumption of fish. The aim of the present work was to determine the ventilation volume of carp, under conditions of pure, aerated water. Materials and methods. Stroke volume and breathing rate of carp representing three size groups (258.7 ± 40.1 g, 449.3 ± 39.6 g, and 663.2 ± 32.3 g) were studied within the temperature range of 10-25°C. Results. At 10°C the stroke volume of carp weighing 200–300 g was on average 2.25 ± 0.63 ml per 1 breath. This parameter in fish weighing 400–500 g was 2.70 ± 0.12 ml·per 1 breath, while in fish attaining 600–700 g it amounted to 3.22 ± 0.41 ml·per 1 breath. The breathing rate of all size groups ranged from 46.2 to 47.4 ± 8.51 cycles per min. A statistically significant increase of the stroke volume was recorded in all size groups at 15°C. At 20°C the increased stroke volume was accompanied by accelerated breathing rate. The temperature increase from 20 to 25°C did not cause any further increase of either breathing rate or stroke volume. Conclusion. The temperature-related regulation of the ventilation volume in carp is a two-step process. At 10-15°C the increased water volume pumped through the gills was achieved by an increased breathing depth (stroke volume). A further increase of the ventilation volume at 15-25°C resulted from acceleration of the breathing rate.
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