The tools of molecular biology provide a rich platform for teaching the scientific process, as interesting questions pertaining to fields such as evolution and ecology can be pursued on short time scales. In this inquiry-based laboratory project, students investigate the authenticity of fish products purchased in local markets and restaurants by DNA sequence analysis of a segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. In the course of their investigation, students are exposed to fundamental molecular biology techniques such as DNA isolation, agarose gel electrophoresis, polymerase chain reaction, DNA sequencing mechanisms, and DNA database analysis. In addition, students will observe how the evolutionary relatedness of species is reflected in the genetic code, and consider how the ecology of fish species influences their product distribution and environmental impact. This project is suitable for advanced high school or undergraduate students.