Effects of acute temperature change on the metabolism and swimming ability of juvenile sterlet sturgeon ( Acipenser ruthenus , Linnaeus 1758)

Summary The objective of this study was to provide information on changes in the metabolism and swimming ability of juvenile sterlet sturgeon, Acipenser ruthenus , caused by acutely low or high temperatures. Changes in critical swimming speed ( U crit ), oxygen consumption rate ( MO 2 ), tail beat frequency ( TBF ) and tail beat amplitude ( TBA ) were observed with a Steffensen‐type swimming respirometer, an oxygen electrode and a camera at different swimming speeds at three temperatures: 5°C, 15°C, and 25°C. Fish tested at 5°C and 25°C were maintained at 15°C (near optimal) for one week to simulate conditions below a dam. The U crit value decreased significantly during acute temperature changes at 5°C and 25°C; U crit was highest near the optimal temperature. Oxygen consumption rate ( MO 2 ) increased with the swimming speed at 15°C; however, at 25°C and 5°C, the MO 2 decreased with the swimming speed. Both TBA and TBF decreased at 5°C and 25°C compared to values at 15°C. The slopes of the regression lines ( TBF /U) at 5°C and 25°C seemed lower compared to 15°C.