The recent development of coalbed natural gas (CBNG) resources has created a need for scientifically sound information by agency, tribal, and industry resource managers in Montana and Wyoming regarding its potential effects on fish assemblages in nearby streams.  Because CBNG development involves production and disposal of coalbed groundwater (often containing high concentrations of dissolved ions, with elevated sodium adsorption ratios and electrical conductivity), as well as surface environment modifications, potential exists for substantial effects on aquatic environments and fauna.  Little research has been conducted on the effects of CBNG development on fish assemblages.  Our objectives are to conduct a comprehensive literature review summarizing all available published and unpublished research on the effects of CBNG development and discharge of coalbed groundwater on fish assemblages and to develop a study plan and proposal to conduct a multi-year research project on the effects of CBNG development on fish assemblages in streams in Montana and Wyoming.