A fish wheel, also known as a salmon wheel, is a device situated in rivers to catch fish which looks and operates like a watermill. However, in addition to paddles, a fish wheel is outfitted with wire baskets designed to catch and carry fish from the water and into a nearby holding tank. The current of the river presses against the submerged paddles and rotates the wheel, passing the baskets through the water where they intercept fish that are swimming or drifting. Naturally, a strong current is most effective in spinning the wheel, so fish wheels are typically situated in shallow rivers with brisk currents, close to rapids, or waterfalls. The baskets are built at an outward-facing slant with an open end so the fish slide out of the opening and into the holding tank where they await collection. Yield is increased if fish swimming upstream are channeled toward the wheel by weirs.
Fish wheels were used on the Columbia River in Oregon by large commercial operations in the early twentieth century until they were banned by the U.S. government for their contribution to destroying the salmon population (see below). The wheel's prevalent use in catching salmon, (in particular, salmon species Chinook, chum, coho, sockeye, and pink) and other anadromous species of fish, has given fish wheels their second name as salmon wheels. Although salmon were prioritized by commercial fishers and Indigenous peoples (albeit for different reasons,) other fish such as steelhead trout (Oncorhynchus mykiss irideus), ooligan (Thaleichthys pacificus), and Pacific lamprey (Entosphenus tridentatus) were also considered valuable catch. While the fish wheel is best known for its presence on the northwestern coast of North America, there is debate whether the technology arrived via Asian migrants who had come to labor in the gold fields, by Scottish and Russian migrants, or was a potentially Scandinavian invention sometime during the turn of the twentieth century.