Effects of environmental hypoxia on oxygen consumption rate and swimming activity in juvenile white sturgeon, Acipenser transmontanus, in relation to temperature and life intervals

Routine oxygen consumption rates (MO2) and swimming activity rates of juvenile white sturgeon were determined using closed respirometers at life-interval-appropriate temperatures: 10° C (0.2 g mean wet weight), 16° C (1.9 g mean wet weight), and 20° C (63.1 g mean wet weight) under normoxic (PO2 > 140 mmHg) and moderately hypoxic (PO2=80 ± 5.0 mmHg) water conditions. At all temperatures and body sizes, hypoxia significantly depressed (p < 0.05) MO2 (57% mean reduction) and swimming activity (70% mean reduction). Overall mean MO2 was 228 µg O2 g-1 wet weight h-1 (normoxia) and 99 µg O2 g-1 wet weight h-1 (hypoxia). Thus, juvenile white sturgeon appear to decrease overall energy expenditures (hypometabolism) during hypoxia via reductions in spontaneous swimming activity. This is a life style that may increase survival during widespread or prolonged environmental hypoxia.