"The End of Fish" was how Daniel Pauly, professor of fisheries at the University of British Columbia, referred to sobering research showing that--without swift action--populations of all major commercial fish species could collapse by 2048. A lesson on the decline of global fisheries can address many state and national science standards. Using an interactive role-play activity is especially effective for enhancing students' scientific discourse and argumentation skills. This article explains how this can be accomplished.