No abstract

Oxygen uptake (M O 2 ) and critical oxygen tension (P crit ) were measured in resting perch Perca fluviatilis that were either fasting or digesting. Digestion caused M O 2 to double (from 61 to 117 mg O 2 kg −1 h −1 ) and was associated with a rise in P crit (from 3·4 to 4·9 kPa), showing that the animal's digestive state must be considered when assessing the effect of hypoxia in natural conditions, and when defining optimal oxygen conditions in aquaculture.