In the eighteenth century, the underwater world became a site of increased investigation. Naturalists produced sumptuously illustrated books and manuscripts that captured its dazzling diversity on paper. By drawing on unique and previously unexplored visual and textual materials from libraries, archives and museums, Fish on Paper offers – for the first time – a history of how the study of fish developed into a distinct field of knowledge, ichthyology. This book shows how ichthyologists established themselves as authoritative knowers of fish through the rise of the classificatory method, defining the very category of ‘fish’ along the way. At the core of such avid attempts to chart living nature were epistemological discussions about how to best preserve fish as specimens, as well as in texts and images. The epilogue reflects on how such historical sources of past species occurrence can inform ecological research in the present.