Bioenergetics of juveniles of red swamp crayfish (Procambarus clarkii).

Procambarus clarkii is an endemic North American crayfish species that was introduced into Spain in 1973 for aquacultural and fishing purposes. Although P. clarkii is a well-studied species for commercial production, there is a great gap in the knowledge of the bioenergetics of juveniles. The aims of this study were to quantify the elements of the energy flow for juveniles of P. clarkii when fed in the laboratory on four different diets. The diets used were: (1) trade commercial feed; (2) various dried algal species; (3) dried Gammarus pulex; and (4) an equal mixture of algal species and G. pulex. The best energetic balance was obtained with diet 3 (greatest energy directed to production P=57%; least energetic investment in respiration R=31%, excretion U=9%, but highest energy loss via faeces F=4%). The poorest energetic balance was observed with diet 4 (P=26.3%; R=55.5%; U=14.7%, but lower energy loss in faeces F=3.5%). The mean O:N relationship was 1.37+/-2.15, implying marked protein catabolism. The utility of studying the bioenergetics of juvenile P. clarkii in laboratory conditions results in the formulation of testable hypotheses about ecological facts and the provision of new insights into the management of their populations in natural environments.