Longnose dace

Rhinichthys cataractae

Order: Cypriniformes

Family: Cyprinidae

Genus: Rhinichthys

The Longnose dace is a small, hardy minnow known for its distinctive elongated snout and powerful swimming ability. Its body is streamlined and slightly flattened on the underside, typically reaching 6 to 10 centimetres in length, with a few individuals growing slightly larger. The dorsal surface is dark brown or olive, while the belly is pale to whitish. Mottling or speckling helps camouflage it against the gravel and cobble of fast-moving streams.

Its most defining feature is the long, downward-pointing snout that overhangs its small, inferior mouth—an adaptation for bottom-feeding in high-current habitats. Longnose dace are built for life in turbulent waters and are often found in riffles where few other small fish can hold position.

Conservation Status: IUCN

Distribution

Found across Canada and much of the northern United States, including the Great Lakes, St. Lawrence River, Hudson Bay, and Rocky Mountain drainages. Also present in cold, clear tributaries of major river systems like the Mississippi and Missouri.

Habitat

Prefers cool, clear, fast-flowing streams and rivers with gravel or rocky bottoms. Common in riffle zones, where water is well-oxygenated and sediment levels are low. Occasionally found in lakes near inlets or outlets.

Requires healthy riparian zones and undisturbed streambeds for spawning and foraging.

Diet

Omnivorous. Feeds primarily on aquatic insect larvae (e.g. mayflies, caddisflies, and midges), small crustaceans, and algae. Uses its long snout and subterminal mouth to graze food from rocks and substrates in strong currents.

Reproduction

Spawns in late spring to early summer in shallow, gravel-bottomed riffles. Males establish territories and court females. Eggs are broadcast over gravel and left to develop unguarded. Fertilized eggs settle between stones, where they are protected from current and predators. Juveniles grow quickly in warm summer waters.

Adaptation

Elongated snout and downward-facing mouth ideal for benthic foraging
Streamlined body and strong fins allow station-holding in fast currents
Cryptic colouration provides camouflage in rocky substrates
Tolerant of high flow and turbulence, outcompeting other minnows in riffles
Wide thermal and ecological tolerance supports broad geographic range

Threats to Survival

Stream siltation and erosion reduce spawning success and foraging visibility
Culverts, dams, and diversions fragment habitats and disrupt flow
Water pollution from agriculture or urban runoff affects sensitive populations
Climate change may alter stream temperatures and flow regimes

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