Montana Field Guide

Longnose Dace - Rhinichthys cataractae

The longnose dace has the most widespread distribution of all fish in Montana. It is found throughout all three of our major drainages. It is very adaptable, inhabiting almost every conceivable habitat: muddy and warm, clear and cold, streams and lakes. The largest longnose dace are about 6 inches long. They are well-adapted for living on the bottom of fast-flowing streams among the stones. Longnose dace eat mostly immature aquatic insects. They are probably one of the most important forage minnows for Montana's larger predatory game fish.

Back olive to black, shading to white or yellow underneath. Sides may have dark blotches. Breeding males have reddish orange on head and fins. Juveniles have a black midside stripe starting at the tip of the snout and ending at the base of the tail fin. Adults often have a dark stripe ahead of eye. Small barbel at each corner of mouth.

Montana Range

Habitat variable. Found in lakes, streams, springs (Brown 1971). Preferred habitat is riffles with a rocky substrate (Morris et al. 1981, Elser et al. 1980).

Eats mostly immature aquatic insects picked off the rocks. Small amounts of algae and a few fish eggs are also eaten (Brown 1971).

Showed a preference for main channel border habitat type in middle Missouri River study (Gardner and Berg 1980). Have declined after formation of Lake Koocanusa on the Kootenai River (Huston et al. 1983, Huston et al. 1984).

Sexually mature probably in 3 yrs. Spawns late spring or early summer at 53 degrees F. in shallow riffle areas over gravel beds (Brown 1971). Middle Missouri River populations spawn early June to latter part of July. Peak in late June (Berg 1981).