Aquatic Nuisance Species: A multi-stage approach to understanding the invasion ecology of exotic crayfish in Northern and Southern California

Biological invasions are widely thought to have major negative impacts on native communities and ecosystems (Vitousek et al. 1996; Parker et al. 1999; Mack et al. 2000). Exotic species are the second most important cause of species extinctions (after habitat destruction) in the United States (Enserink 1999) and an important cause of losses in biodiversity worldwide (Sala et al. 2000). From an economic, resource management view, exotic species can have major direct and indirect impacts on commercially-important natural resources – e.g., fisheries, crops (Pimentel et al. 2000). Although exotic species can impact native species via various mechanisms (e.g., competition, spread of disease, hybridization), for aquatic animals, a key mechanism is clearly predation (Moyle and Light 1996; Gamradt and Kats 1996; Knapp et al. 2001). Thus an important goal on the interface between basic and applied ecology is to understand the ecology of potentially damaging invasive predators (including omnivores), in order to minimize their negative impacts