Hypoxia tolerance variance between swimming and resting striped bass Morone saxatilis

Individual striped bass Morone saxatilis were each exposed in random order to aquatic hypoxia (10% air saturation) either while swimming at 50% of their estimated critical swimming speed (Ucrit ) or while at rest until they lost equilibrium. Individuals were always less tolerant of hypoxia when swimming (P < 0.01); the average fish was over five times more tolerant to the same hypoxia exposure when not swimming. There was no relationship between an individual's rank order of hypoxia tolerance (HT) under the two flow regimes, suggesting that different factors determine an individual's HT when at rest than when swimming.