We propose to evaluate application of ammonium chloride for the purpose of removing invasive Northern crayfish (Faxonius virilis, formerly Orconectes virilis) and Red swamp crayfish (Procambarus clarkii) from aquatic systems. Adding small amounts of ammonium chloride to aquatic systems may be a cost-effective and low-impact way to eradicate invasive crayfish and support conservation of native aquatic species. We will first evaluate dosages and concentrations in the laboratory and then utilize the information derived from those laboratory studies to conduct removal of crayfish from small stock ponds in the field. A minimum of two treatment ponds will be evaluated over a season to evaluate effectiveness. This project will provide necessary information for potential licensing and registration of an ammonia-based chemical tool for management of invasive crayfish. New tools are desperately needed for control of invasive crayfish in stream systems, but toxicity trials and methodology must first be established in more controlled laboratory and pond settings.