Native and alien crayfish species: do their trophic roles differ?

Abstract

AbstractFreshwater crayfish are regarded as ecosystem engineers and keystone species. They act on various trophic levels and influence plant and animal species, community-level properties, and ecosystem processes. Comparisons of native and alien crayfish suggest greater negative effects of alien than native crayfish, but the species-specific roles of native and alien crayfish remain unclear. We used 2 enclosure experiments in streams to study biomass-related effects of the native Astacus astacus and Austropotamobius torrentium and the alien Pacifastacus leniusculus on available food types and the potential fate of these nutrients in the stream food web. In experiment 1, we compared the effects of crayfish (2 densities and a no-crayfish control) on leaf breakdown, production of leaf fragments, and accumulation of fine particulate matter (FPM). In experiment 2, we investigated predation by individual crayfish on Gammarus, Hydropsyche, and Arctic Char carrion. Pacifastacus leniusculus had stronger effects on...