Longnose Dace

Longnose dace can be mistaken for suckers because of their subterminal "sucker-like" mouth. However, longnose dace (like all members of the family Cyprinidae) lack small fleshy projections, called papillae, on their mouths.

Juveniles have a black lateral line that extends from the beginning of the eye to the caudal fin that fades as the fish matures. The lateral line in juveniles is not present in all populations. In adults, the dorsal side is dark green to black, the lateral side is darkish to silvery with mottling often present, and the ventral side is pearly.

Longnose dace have the widest distribution of any cyprinid in North America, with a range reaching as far south as the Rocky Mountains in northern New Mexico and as far north as the Mackenzie River near the Arctic Circle and across the continent from the Pacific to Atlantic coast. Multiple refugia during the most recent glacial maximum may explain the broad geographic distribution of longnose dace. There were up to three possible glacial refuges during Pleistocene glaciations: the Pacific, the Mississippi and the Atlantic. Longnose dace on the Quebec peninsula likely originated only from the Atlantic refuge, in contrast to other fish species on the peninsula that originated from multiple refugia. Longnose dace in northwestern North America originated from a Pacific refuge.

Longnose dace occur in moderately cool water streams, rivers and lakes with temperatures up to 22 °C (72 °F). Longnose dace are benthic and preferentially occupy rock and gravel substrate. During the day longnose dace hide under rocks. Longnose dace prefer shallow, fast-moving riffles in streams and rivers and the turbulent, near-shore region of lakes.

Longnose dace are opportunistic foragers. Small longnose dace (≤ 50 mm (2.0 in)) primarily consume algae and benthic invertebrates dace (> 50 mm (2.0 in)) feed on fish scales, fish eggs, terrestrial insects, and aquatic benthic macroinvertebrates, although diet varies seasonally. They are nocturnal feeders, possibly to avoid predation and/or salmonid competitors.

Longnose dace have small home ranges and high site fidelity, however there is evidence that a small proportion are able to disperse distances greater than 500 km (310 mi).