Feeding preference of the red swamp crayfish Procambarus clarkii (Girard) on living macrophytes in a Spanish wetland

Abstract

We carried out field studies and laboratory experiments to investigate (1) the possible feeding preference of the red swamp crayfish Procambarus clarkii on living macrophytes, and (2) the influence that such a feeding preference can cause on the distribution and bundance of P. clarkii in wetland systems. Field studies, at two sampling areas of the Spanish wetland Tablas de Daimiel National Park (TDNP), showed that P. clarkii had significantly higher mean values of density and biomass at S-2 (with Char a hispida as the dominant macrophyte) than at S-1 (with Ceratophyllum submersum as the dominant macrophyte). Laboratory experiments showed that P. clarkii had a significant feeding preference for C. hispida versus C. submersum. Analyses of the biochemical composition of each macrophyte species showed that the unpreferred macrophyte (C. submersum) had higher amounts (per unit of biomass) of total protein, nitrogen, phosphorus, sodium, potassium, magnesium and phenolic compounds than the preferred macrophyte (C. hispida). By contrast, C. hispida had more calcium per unit of biomass than C. submersum. Overall, we conclude that the presence of higher amounts of phenolic compounds in C. submersum might be the foremost factor responsible for the observed feeding preference of P. clarkii on living macrophytes in TDNP.