Experimental studies on thermal behaviour and diurnal activity rhythms of juvenile European sturgeon (Acipenser sturio)

Experiments were performed to determine the temperature preference of juven ile sturgeons. The biorhythms of activity and the location of fish in a the rmal gradient of an electronic shuttlebox were registered. The fish showed dominant 24 h activity rhythms with its maximum at the nighttime. A tempera ture preference range or an active thermoregulatory behavior could not be d emonstrated by our experiments. The behavior of sturgeons was influenced by temperature: activity and swimming speed were positively correlated to ris ing temperatures. There are indications that the fish could have been attra cted by low light intensities at night.