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

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White Sucker
Catostomus commersoni

What do they look like?

A large-scaled sucker with 10-13 (usually 11-12) dorsal rays. In profile, the body tapers gradually back from the dorsal fin to the relatively deep caudal peduncle; the caudal peduncle depth is usually more than half the width of the dorsal fin base. The snout is short, blunt and, when viewed from below, scarcely projects beyond the upper lip. In profile, the hind margins of the lower lip barely reach the front half of the nostril and the head is cone-shaped. In B.C., spawning white suckers lack conspicuous lateral bands.

Where do they live?

In B.C., white suckers occur in both rivers and lakes, although west of the Rocky Mountains they are relatively uncommon in large rivers. Information on habitat use by adult white suckers in both lakes and rivers is scarce in British Columbia. In the upper Peace system (Parsnip River) adults are found over mud-silt substrates in low gradient sections of the main river during the summer. At about the same time, adults move downstream into the lower reaches of the Parsnip River near Williston Reservoir.

In upper Peace lakes (Crooked River system) juvenile white suckers are associated with shallow water and weedy areas during summer. In the Parsnip River system juveniles are reported to concentrate in the lower reaches of tributary (presumed spawning) streams and in marshes associated with small lakes.

During the summer, in the Crooked River system, white sucker fry (35-45 mm in total length) are abundant in the littoral zones of many of the warmer lakes. Here, they are associated with the shallow weedy regions. In summer, white sucker fry are uncommon in large rivers but, where they occur, they are again associated with shallow weedy areas and soft substrate.

What is their life like?

In B.C., white suckers spawn in the spring (mid-May to mid-June), usually after water temperatures reach about 10 to 12 °C. Apparently, white suckers return repeatedly to specific spawning streams and this suggests homing behaviour. In the outlet to Summit Lake (Crooked River) white suckers were observed spawning in early June (water temperature 15°C). Most lacustrine populations spawn in streams (usually inlet streams) but lake spawning is also common.

In streams and rivers, spawning usually occurs on shallow riffles (<1 m deep) adjacent to deeper areas. Apparently, substrate size is important and typically consists of coarse gravel rather than sand. In lakes, spawning also occurs over gravel (submerged stream deltas, and shallow gravel shoals). White suckers spawn mainly at night. There is no site preparation, the substrate is often cleaned by the thrashing of spawning fish. In B.C., white sucker fecundity varies roughly between 10,000 and 50,000 eggs. The eggs are adhesive. Some stick to the gravel surface but the current carries others into crevices among and beneath rocks. Development rate is temperature dependent, and hatching occurs in about a week at 16 °C and at about 21 days at 10 °C. The newly hatched larvae are approximately 9 mm in total length. Feeding starts at 12 to 13 mm and the mouth becomes ventral at roughly 20 mm.

Growth rates are variable in white suckers and probably constrained by both population density and food supply. In B.C., the largest young-of-the-year reach a length of slightly over 60 mm by the end of their first summer. Age at maturity is dependent on early growth rate. Minimum ages at sexual maturity in B.C. are 3+ for males and 4+ for females. Little age data in BC exists for white suckers, but the maximum age for a Missouri population was 18 years.

What do they eat?

As adults, white suckers are benthivores but like many fishes they begin life as planktivores. Early in life the mouth is terminal but slowly shifts to a ventral position and is clearly subterminal by about 20 mm. When the mouth is terminal the larvae feed primarily on water column prey (cladocerans and rotifers), but as the mouth shifts to a ventral position their diet becomes more diverse as algae, ostracods, and the larvae and pupae of aquatic insects (especially chironomids) are added to the diet. Adults feed on a wide variety of aquatic insects. However, chironomids usually remain the dominant food item.

What is their distribution? The white sucker is a widespread eastern North American species that crossed the Continental Divide into central British Columbia some time during deglaciation. East of the Rocky Mountains the white sucker ranges from the lower Mackenzie River south across the Great Plains to New Mexico and Oklahoma, east to Labrador and Nova Scotia in the north, and south to Georgia. In B.C., white suckers are widespread and common in the northeastern portion of the province (e.g., upper and lower Peace system and lower Liard system). White suckers also occur in the upper Liard (above the Grand Canyon). White suckers are also abundant in the Fraser system (lakes and rivers) in the Prince George and Quesnel regions. From the upper Fraser white suckers apparently spread into the Skeena system where they are now common.

View Peace Williston distribution map.