The Peace/Williston Fish and Wildlife Compensation Program (PWFWCP)

View Larger Photo

Longnose Dace
Rhinichthys cataractae

What do they look like?

A ventrally flattened minnow with a long snout (as much as 50% of its head length) that clearly overhangs the mouth. Upper lip firmly attached to the snout; mouth is horizontal and with well developed barbels at the corner of the jaws. Darkish dorsally, darkish to silvery laterally with mottling often present. In specimens less than 100 mm in length usually there is a distinct dark mid-lateral stripe that is constricted at the posterior end and then expands again on the tail as a dark spot.

Where do they live?

There is no published information on lacustrine populations from B.C. but data from Lake Winnipeg and Lake Michigan suggest that the life history of lacustrine longnose dace is basically the same as that of riverine populations. Some observations on habitat use by fluvial longnose dace are available for B.C.

The body shape and fin shapes of longnose dace suggest a fish adapted to fast water and, in B.C., they have been collected from riffles with surface velocities of up to 1.8 m/s. Although associated with fast water, the actual microhabitats used by adults may have much lower water velocities. Typical adult habitats have substrates of loose fist-sized, or larger, rocks. In most of the B.C. Interior, adult longnose dace shift from riffles to slower, deeper water in the winter, but in the lower Fraser Valley they stay on riffles year round. There is some evidence of seasonal movements (presumed migrations) by adults.

As young longnose dace grow, swimbladder growth does not keep pace with the rest of the body. This results in a gradual increase in density. Consequently, during their first winter the juveniles usually become bottom-dwellers and move into riffles where they occupy habitats similar to, but with less overhead turbulence than those used by adults. Field observations suggest that during freshets, yearlings move back into quiet water and seek shelter along river edges.

In small streams, young-of-the-year are found in shallow pools, backwaters and other low velocity areas. Such areas usually have silt or sand substrates and the neutrally buoyant fry swim above the bottom. In large rivers, young-of-the-year often aggregate in quiet midwater areas. In lakes, young-of-the-year longnose dace are also found in quiet water, usually close to shore and in areas where there is cover.

What is their life like?

In B.C., longnose dace begin spawning in the spring when water temperatures rise above 10 °C (May to early July). Spawning occurs on riffles over coarse gravel substrates. Males are territorial and defend a small area of cleaned gravel where females deposit eggs. Females do not deposit all of their eggs in a single spawning and usually spawn with more than one male. Fecundity varies with female size and, in B.C., the smallest mature females are about 55 mm in fork length and produce around 150 eggs while the largest females (over 120 mm) produce in excess of 2,000 eggs. The eggs are adhesive. They are deposited in clumps amongst the gravel within the male's territory.

Depending on temperature, the eggs start to hatch in about a week. Newly hatched fry are about 6 mm in total length and reach about 8 mm before the yolk is absorbed and feeding begins.

At most B.C. sites, young-of-the-year (0+) longnose dace reach a fork length of 20-35 mm by the end of their first growing season. Typically, longnose dace reach sexual maturity at the end of their second summer and spawn for the first time the next spring (2+). Typically, these fish can live up to 5 years old.

What do they eat?

The longnose dace is a bottom living species and, hence, its food habits are directly related to bottom-living organisms. This species forages primarily at night. Longnose dace have well developed maxillary barbels and one study suggests the barbels function in food location.

The diet of fluvial adults consists primarily of the larvae of aquatic insects, especially those associated with riffles. In the fall, however, some terrestrial insects appear in stomach contents. Adults occasionally prey on larval fish. In lacustrine populations the adult diet is similar to that found in flowing water (i.e., primarily the larvae of aquatic insects) but also includes snails, oligochaetes, and pea clams.

Unlike adults and juveniles, young-of-the-year longnose dace forage actively during the day. Their diet consists primarily of chironomid larvae but also includes significant quantities of periphyton (algae and diatoms).

What is their distribution? The longnose dace has the widest distribution of any North American minnow. It occurs across the entire breadth of the Continent (from Labrador to coastal British Columbia) and from the upper Mackenzie Delta to northern Mexico. In B.C., longnose dace are found in suitable habitats from the Columbia and Fraser systems north to the Liard River. It also occurs in coastal drainages that rise on the Interior Plateau and flow west through the Coast Range to the sea, but is absent in most of the short rivers along the British Columbia coast.

View Peace Williston distribution map.