<jats:p>Water temperature exhibits a strong influence on the regional variability in activity of the 7-ethoxyresorufin-O-deethylase (EROD) in the liver of dab (Limanda limanda) from the German Bight during the spawning and postspawning seasons. The relationship between EROD activity and water temperature found in situ was, surprisingly, not masked by migrations of dab. Correlations between EROD activity and temperature could not be explained by a direct temperature effect in terms of temperature compensation. Instead, we suppose that temperature influences EROD activity indirectly via its influence on the duration of the gonadal cycle and thus on the time of spawning, which we assume to be coupled with the seasonal variation in EROD activity. Significant negative correlations between EROD activity and the condition factor, gonadosomatic index, and liver-length index could be attributed to the parallel or opposite temporal changes of these parameters. In the liver of spawning females, no linear relationship was detected between the EROD activity and the concentration of the polychlorinated biphenyls (PCB), which have been previously determined.</jats:p>