Abstract
Abstract The effects of water temperature, salinity and pH on non-faecal nitrogen excretion rate in fingerlings of two sturgeon species and two hybrids weighing 5–21 g were investigated. The effect of temperature on ammonia and urea excretion rate was examined in specimens acclimated to 12, 16, 20, 24 and 28°C. Ammonia and urea excretion rate increased following a temperature rise from 12 to 28°C by 2.7 and 2.9 times, respectively. This relationship is described by a linear equation: E = a + bT . During the acclimation to salt water, the ammonia excretion rate decreased while urea excretion increased. Sturgeon fingerlings, under isoosmotic salinity, excreted more urea and less ammonia than under hypoosmotic concentration. Ammonia excretion decreased with an increase of water pH from 4.0 to 9.6; the relationship is described by the equation: E = P b . The exposure to alkaline water (pH = 8.9 and 9.4) caused a rise of the urea share in non-faecal nitrogen excretion to 50%.
Published Version
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