Fish Metabolism Fundamentals

Because fish are ectothermic, their metabolic rate is roughly one-tenth of a same-sized mammal at rest. Cold water slows metabolism further - Arctic fish process food over weeks, not days. Metabolism is measured as oxygen consumption; fisheries use metabolic scope (max rate minus resting rate) as the foundation of aerobic capacity models.

A Greenland shark digests a meal over weeks; a warm-water bass processes the same amount in a day. The Q10 effect - metabolic doubling per 10 C - explains most of the difference.