Abstract

The physiological and ecological adjustments of Procambarus clarkii in different seasons at Doñana's freshwater marsh are described. Doñana National Park (DNP) has been the focus of considerable attention in large scale conservation since the 1980s. Efforts to restore DNP’s freshwater marsh have intensified as a consequence of an exotic crayfish (Procambarus clarkii) introduction. However, data from ecophysiological studies conducted after 1994 allowed the assessment and prediction of environmental impact by this species. This North American astacid has caused a substantial reduction of submergent aquatic macrophyte prairies due to its broad trophic spectrum and feeding habits, which changed the environmental frame from a clear water equilibrium to a turbid water balance. Studies of the aerobic, excretory metabolisms and population dynamics of crayfish belonging to several ecosystems along three complete hydrological cycles were made. Physiology in situ was studied as well as laboratory experiments to determine oxygen and nitrogen excretion rates by using several environmental conditions (temperature, water regime, environmental oxygen concentration and photoperiod). Data readings were taken every 6 h for 24 h while also recording habitat conditions. Metabolic tests were conducted to evaluate population energy requirements to maintain optimum growth and reproduction at different seasons of the year. Analysis suggested that several factors influence the metabolism of the animals, specially their spawning. The major factor was water regime. Temperature does not seem to be important since its variations within each season does not reach the physiological extremes of this clinocynetic species.

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