Physiology of Finfish and Shellfish (2+1)

4.1.6. Oxygen Effects

Over a broad range of dissolved oxygen (DO) concentrations at a given temperature and activity level, a fish has a constant metabolic rate. There is a critical point of DO, however, below which a fish cannot extract enough oxygen from the water to support its metabolic rate. At this point, a fish begins to accumulate oxygen debt. That is, it must generate some of its ATP from anaerobic sources (glycolysis) and lactate, which it cannot further oxidize, accumulates in the tissues. A fish cannot live indefinitely below the critical point. At some point, as DO continue to fall, the fish is unable to sustain life anaerobicly and death from asphyxiation occurs.