Environmental factors controlling crayfish Procambarus clarkii activity in the Donana National Park freshwater marsh (SW-Spain)

We investigated how environmental factors control crayfish (Piocambarus clarkii) activity in Donana National Park freshwater marsh where this species was introduced in 1974. In order to extrapolate data to different ecosystems of the freshwater marsh, a pond called Lucio El Palacio was used as an experimental site and flooded artificially to simulate natural different flooding patterns of the freshwater marsh. Measurements were taken in situ during 24 h while also recording habitat conditions. We measured crayfrsh Q(O2) (mg g(-1) h(-1)), reproductive stage, sex and stomach filling content, and habitat d(O2), and temperature. There were no significant differences in activity patterns of crayfish between different hydrological conditions, but there were differences in levels of oxygen consumption (P > 0.05). Photoperiod and oxygen availability had a large effect on activity, with the highest levels of oxygen consumption occurring at nightfall. P. clarkii act as oxygen-conformer species until O-2 availability in medium was 5 mg l(-1); when O-2 availability is higher than 5 mg l(-1), animals behave like oxygen-regulator species. Mature animals had higher metabolic rates than immatures. Males were more active than females. The effect of temperature is confounded with that of time and does not seem to be important since its variations within each season is very low and does not reach the physiological extremes of this species.