decreased mitochondriai oxygen consumption Asustained swimming session d muscie in vitro exercise used here was perhaps but increased Ros production in both eel stages. The swimming intense to induce a stimulation of mitochondrial function or biogenesis even when antioxidant enzyme activities were unchanged. idantlantioxidant imbalance by lipid peroxidation increased in yellow but significantly decreased in silver eels.The silvering process therefore appears to allow a pre-adaptation of red muscle radical metabolism to the demands ofspawning migration.