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

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Pygmy Whitefish (Non-Game Fish)
Prosopium coulterii

What do they look like?

A large-scaled whitefish that is dark brown on top, silvery on the side, and whitish below. The body (generally less than 120 mm) is round in cross section and the snout usually is blunt and rounded when viewed from above. It has a small adipose fin (its base is about equal to the eye diameter). Its eyes are situated slightly higher up on top of its head when compared to other whitefish. Adult pygmy whitefish are easily confused with juvenile mountain whitefish. Usually, dorsal fin ray numbers will separate the species: 9 or 10 in pygmy whitefish and 11 - 15 rays in mountain whitefish. Juveniles and most adult pygmy whitefish have well-developed parr marks.

Where do they live?

Relatively little is known about habitat use by pygmy whitefish in British Columbia. They are mainly a coldwater species (usually found in water < 10 °C) that occurs in lakes and rivers. In the south and central parts of the province they are restricted to relatively deep lakes and there is probably little gene flow between populations. However, glacial rivers in the southeastern portion of the province contain fluvial populations (Kicking Horse River). In the northern parts of the province both lacustrine and fluvial populations are relatively common. Sometimes, they are found in shallow water and a number of factors may affect their inter lake distribution. The use of deep water in lakes is not obligatory but depends on what other fish species (predators or competitors) are present. In rivers, pygmy whitefish are found in both turbid and clear waters with moderate to swift current and, usually, over gravel or cobble substrates. In flowing water, no observations are available on the habitats used by either young-of-the-year or juvenile pygmy whitefish.

What is their life like ?

Pygmy whitefish spawn in late autumn or early winter usually when water temperature is less than 5 °C. There is no detailed description of either spawning sites or spawning behaviour. Nonetheless, schools of pygmy whitefish have been observed in lakes holding near the mouths of inlet streams and in rivers holding in pools just below riffles. Circumstantial evidence suggests pygmy whitefish also spawn in lakes. Like most fish, fecundity increases with body size and ranges from as low as 100 to over 1,100 eggs. The incubation time is unknown but, presumably, they incubate over winter and the fry emerge in the spring or early summer.

Young-of-the-year growth descriptions are rare and descriptions of growth usually begin with fish in their second growing season during which average size varies dramatically among lakes. The smallest described adults are about 65 mm and the largest known adults average about 250 mm (Maclure Lake, B.C.). The oldest pygmy whitefish recorded in the upper Peace system was in its seventeenth year, but in most populations, fish older than 9+ years are rare.

What do they eat?

Most studies indicate that pygmy whitefish are predominately benthic foragers with lake-dwelling populations feeding on chironomid larvae and pupae, Chaoborus, cladocerans, small mollusks, ostracods, and amphipods. In some cases, however, they also forage on zooplankton in the pelagic zone. Fluvial populations feed heavily on chironomid larvae and pupae but also include the nymphs of other aquatic insects in their diet.

What is their distribution? In the past, pygmy whitefish were thought to be confined to North America but, recently, they were discovered in three lakes in the Amguem River system on the Chukotsk Peninsula, Siberia. In North America pygmy whitefish can be found east of the Continental Divide but are uncommon. West of the Continental Divide, they are more common and widely distributed where they occur from the Columbia River system (northern Washington, Idaho, and inter-mountain Montana) to the Bristol Bay region of Alaska. In the Williston Watershed, these fish are known to inhabit Williston Reservoir along with 18 other surrounding lakes.

View Peace Williston distribution map.