The rising incidence of invasive species displacing endemics and altering water chemistry and local foodwebs increasingly affects freshwater systems and should be considered a water quality problem (Carr and Neary 2008). Aquatic species have in many cases been introduced deliberately into distant ecosystems for recreational, economic, or other purposes. In many instances, these introductions have decimated endemic fish and other aquatic organisms, and they can also degrade local watersheds. Other species have invaded inadvertently, transported on the hulls of recreational watercraft or in the bilgewater of commercial boat traffic. For example, invasive species such as zebra (Dreissena polymorpha) and quagga.
