Feeding habits of the crayfish Austropotamobius pallipes (Decapoda, Astacidae) in a brook in Latium (central Italy)

The several studies regarding the feeding habits of freshwater decapods have provided a few detailed descriptions of their natural diets and have seldom analysed variations in their feeding habits due to season, size, age, and changes in their physiological state. This situation led us to analyse the stomach content of different age classes of the crayfish Austropotamobius pallipes, in order to increase the knowledge available on this species' diet. Ingestion index, vacuity frequency, and occurrence frequency were calculated; then, a graphical representation was carried out only for the animal component (mainly insect larvae) observed within the stomach. The results show A. pallipes to be an omnivorous and opportunistic animal. Its diet includes the exploitation of more easily accessible vegetal and detritus resources, which are the main sources of energy and proteins in freshwater ecosystems. Invertebrates are very important for the crayfish diet; in fact, the animal component, and in particular Tricoptera, Diptera, and shellfish, plays a very important role for juveniles and adult females. Feeding strategies might reduce competition between sexes, satisfying their energetic and nutritional needs. The acquired knowledge of the crayfish trophic niche may be used, for example, to improve the diet of animals kept in captivity.