Diet of the red swamp crayfish Procambarus clarkii in natural ecosystems of the Donana National Park temporary fresh-water marsh (Spain)

As a result of the introduction of the crayfish Procambarus clarkii, the functioning and structure of the fresh-water marsh in the Donana National park have been dramatically altered. Because those changes have been attributed mostly to trophic interactions between the crayfish and existing food webs. the aim of this study was to explore the diet of this species in natural ecosystems in this park. A total of 502 stomachs was analyzed from 3 sites on 2 dates (March and May). The stomach contents were classified into 13 food categories. The most frequent food item in the population was non-green plants (80% occurrence in the pooled data), followed by rhizomes of Scirpus sp. (50%), green plants (36.8%), and organic sediment (30.1%). Animal food items were represented mainly by insects (24.9%), which included a wide variety of aquatic larvae. cladocerans (16%), and Gambusia holbrooki (14%). Both immature and adult size-classes of this crayfish ingested mainly plants and organic detritus, but a higher proportion of food of animal origin has been found in young (<30-mm carapace length) compared to adult crayfish. The mean number of food categories per stomach varied between 2 and 3, and no significant differences were found between seasons, sexes, and size classes (ANOVA, P > 0.05), except for March when we found lower means in the Manecorro and La Rocina stations than during May, The trophic index calculated was D = 25.3. Thus, the diet of P. clarkii indicates that this crayfish is a polytrophic species.