Effects of exercise and temperature on geosmin excretion by European eel (Anguilla anguilla)

The presence of geosmin in fish products causes an earthy or musty off-flavour. To avoid economic damage resulting from market entrance of off-flavoured fish products, fish farmers utilize the reversibility of geosmin uptake to depurate the off-flavours from their fish crops by holding them in clean water just before harvest. To improve this process, effects of exercise and temperature on the excretion of geosmin by European eel (Anguilla anguilla) were assessed. Fish loaded with geosmin were depurated for 23 h during which they were subjected to combinations of exercise (spontaneous swimming activity at 0.05 m s- 1 or forced swimming at optimal swimming speed of 0.55 m s- 1) and temperature (15 °C or 25 °C) treatments. Oxygen consumption was measured during depuration. Whole body geosmin concentrations were measured in samples collected at t = 0 and t = 23 h to assess geosmin excretion. Geosmin excretion by European eel was clearly enhanced by exercise, but temperature had no statistically significant effect. Exercise increased oxygen consumption, which in turn showed a positive linear relation with geosmin excretion. These findings support the idea that the physiological responses aimed at increasing oxygen uptake also affect the branchial exchange of lipophilic xenobiotic chemicals between the fish and its surroundings. Exercise can be used to reduce the time required to depurate off-flavours from fish. These findings are relevant for aquaculture industries confronted with off-flavoured fish crops