Abstract
Work on short-term consumer dynamics in open ecosystems (e.g. stream living mayflies) suggest that resource supply determine consumer abundance. However, our field data indicate that the abundance of long-lived omnivores (signal crayfish) is regulated by trout predation or substrate availability (i.e. cannibalism), but that crayfish size is regulated by resource supply. The aim of this project is to test how multiple factors simultaneously influence the recruitment and growth of stream-dwelling signal crayfish. The knowledge gained from this project will increase our ability to optimize crayfish production in different types of streams. The knowledge gained is also of general interest since we investigate the mechanisms influencing consumer dynamics in open systems dominated by larg-bodied and cannibalistic omnivores. Three stream channel experiments will test the following hypotheses: 1) Recruitment of juvenile crayfish in streams with a low density of trout is regulated by adult crayfish and substrate size. 2) Recruitment of juvenile crayfish in streams with a high density of trout is regulated by predation, but only when the input of terrestrial drift-food for trout is low. 3) Growth of juvenile crayfish is regulated by resource supply. 4) Adult crayfish induce emigration of other invertebrates and influence resource supply (detritus) and have significant effects on juvenile survival and growth in detritus based systems.
Sweden