Updated July 2019. Fishes of the genus Cottus –the sculpins— have long been a challenge for fish managers and ichthyologists in the West. They share streams, rivers, and lakes with trout and salmon, and depend on the same kinds of habitats with relatively cold, clean water. Yet we don’t know how many kinds of sculpins there are. The morphological differences between species are so subtle that even experts are occasionally baffled. Thus, it seems likely that the biodiversity of sculpins in the West is underestimated and unappreciated.