Direct and indirect effects of carp (Cyprinus carpio L.) on macrophyte andbenthic communities in experimental shallow ponds in central Mexico

An experiment was conducted for 11 months in five controlled small ponds (a pproximate to 0.05 ha) to determine the effects of common carp on water tur bidity, and macrophyte and benthic communities in subtropical shallow syste ms. By using exclosures in ponds, we also looked for carp direct effects (b y predation disturbance) and indirect effects (by increasing turbidity, and decreasing refuge sites) on rooted macrophyte and benthic communities. Res ults showed that at densities equal or higher than 0.8 ind. m(-2) carp suff ers from intraspecific competition. At the same densities, carp produces an increment of water turbidity, but the relation is non-linear, suggesting a switch effect, from a clear-water-system to a turbid-water-system. We also found that a direct effect of carp on macrophytes depends on the susceptib ility of each species. Carp affects benthic abundance directly by predation , but its indirect effects on it remain unknown.