Hydrology is among the most important environmental factors influencing the ecology of riverine organisms; altering existing habitats; affecting the availability of riparian habitats; and affecting organism dispersal, spawning location and frequency.  Dams, urbanization, riparian development, stream diversions and other anthropogenic factors alter flows in manners that affect many species and can result in changes in species assemblages.   The success of aquatic nonnative species, including undesirable exotic organisms, is also affected by hydrologic factors, but because individual species have different needs and preferences, nonnative species may be affected differently, either aided or hindered, by the extant hydrologic regime.  For example, Asian carps are thought to be highly dependent on hydrograph peaks for spawning, on current and turbulence for survival of the eggs, and on access to low velocity shallow areas for nursery habitats.  Flooding can provide pathways for nuisance species to disperse to new habitats simply by inundation of the intervening terrestrial areas.  Alternatively, flooding can be an important means to flush nuisance nonnative species from canyon-bound systems in Western streams, while having little effect on native species adapted to high-flow events.

The goal of this symposium is to provide an opportunity to explore the effects of hydrograph on the success of nonnative species and to examine where understanding these relationships is useful in risk assessment, and where manipulation of hydrograph or other hydrologic variables might be useful in nuisance non-native aquatic species control.