Freshwater Fishes of the Columbia Basin Return to Table of Contents

The Columbia River Basin in British Columbia

From the Source
Located in southeastern British Columbia, the Columbia River Basin drains over 100,000 square kilometres and ranks as B.C.'s third largest river drainage behind the MacKenzie and Fraser river systems. The source of the Columbia River, at Columbia Lake, is hemmed high inland among mountains characteristic of the western North American Cordillera. From its origin the Columbia River flows north along the Rocky Mountain trench, fed by the Spillimacheen and Kicking Horse rivers until arching around the northern tip of the Selkirk Mountains in a large bend near Mica Creek. From Mica Creek the Columbia River continues south past Revelstoke, B.C. and moves into the Arrow lakes chain. At Castlegar, B.C., the Columbia widens as it is met by the Kootenay River and continues south until crossing into Washington State near Trail, B.C.

Major Tributaries (Regions)
The Canadian portion of the Columbia Basin can be divided into eight regions based on watersheds and fish assemblages (McPhail and Carveth 1994). The regions are: the upper Columbia, lower Columbia, upper Kootenay, lower Kootenay, Similkameen, Okanagan, Kettle and the Flathead.

Major tributaries and regions of the Columbia Basin in British Columbia

The upper Columbia and upper Kootenay rivers are fed from the cold, turbid, glacier fed tributaries of the Rocky Mountains. The fish fauna of these regions is largely limited to species well adapted to cold water environments such as char, trout, whitefish, and some sculpins. The upper Columbia region extends from the river's source at Columbia Lake, past Mica Creek, through to the northern end of the Arrow lakes. The upper Kootenay River runs south through Canal Flats, B.C. and passes a mere 2 km from the headwaters of the upper Columbia River at Columbia Lake. From its highland headwaters the upper Kootenay River flows due south until crossing into the U.S.A. near Creston, B.C., where the name changes to Kootenai.

The lower Columbia and lower Kootenay regions are warmer, slower waters than the upper reaches, and they consequently support a more diverse fish fauna including: sturgeon, suckers, minnows as well as char, trout, whitefish and a variety of sculpins. The major feature associated with both the lower Columbia and lower Kootenay regions are two large lakes (Arrow lakes, Kootenay Lake). The lower Columbia River moves south through the Arrow lakes and gains speed at the lake outlet near Castlegar, B.C. From Castlegar, the lower Columbia continues south, fed by the Pend D' Oreille River at the site of Waneta Dam before crossing into the U.S.A. The lower Kootenay region extends from the point where the Kootenay (Kootenai) River re-enters Canada near Creston, B.C., through Kootenay Lake's west arm, to the river's confluence with the lower Columbia River at Castlegar, B.C.

Many of the high gradient tributaries of the Columbia and Kootenay rivers contain natural escarpments and ancient volcanic terrain that act as fish-proof distribution barriers (Daly 1912). The fish fauna associated with these isolated regions commonly contain unique forms of char, trout, sturgeon and sculpins that have remained reproductively isolated from the main rivers since the Columbia Basin was repopulated with fish postglacially approximately 9,000-13,000 BP. Bonnington Falls (now the site of Bonnington Dam), escarpments along the steeper tributaries of the lower Columbia, and the Pend D' Oreille Gorge (now flooded by Waneta Dam) are some examples of geologic features that have steered the distribution of Columbia Basin fish species.

Waterfall barrier isolating fish populations on Pass Creek at Robson, B.C.

Regions west of the mainstem Columbia River, include the Similkameen, Okanagan and Kettle river systems. These systems have a native fish fauna similar to that of the lower Columbia River, but have been heavily impacted by the introduction of exotic, non-native species since the turn of the 20th C. These drainages empty the southern Interior Plateau and Monashee Mountains, and eventually meet the mainstem Columbia River south of the 49th parallel in Washington State. A natural velocity barrier on the Kettle River at Cascade, B.C., has prevented the upstream dispersal of several endemic species, and a similar distribution pattern is observed in the Okanagan River below the barrier at Okanagan Falls.

The Flathead River region is an isolated watershed located east of the Rocky Mountain trench in the extreme southeastern corner of B.C. The Flathead system is a cool headwater tributary of the Pend D' Oreille River system and contains a sparse, cold-water fish fauna -- the origins of which are complex and poorly known. Although the Flathead region is meager in terms of the number of species it contains, it does, however, contain a community of sculpins that has proven very puzzling to taxonomists. The geologic and glacial history, and the faunal assemblage of the Flathead River suggest that the Flathead Valley shared historical connections to the Missouri River drainage and Great Basin of the Mississippi River east of the Rocky Mountain Divide (Daly 1912; Dowling 1917; MacKenzie 1916; Stewart and Lindsey 1983).

The Origin and Nature of the Columbia Basin Fish Fauna
The fish fauna of the Columbia Basin is one of the most distinct in North America. In B.C., the Columbia Basin houses 43 fish species from 11 families, of which 27 are native species and 16 are introduced species (McPhail and Carveth 1992). Nine of the native species are endemic to the Columbia Basin, and it is these species that set the fish fauna of the Columbia Basin apart from those beyond the North American Cordillera.

It is widely accepted that the present distribution of freshwater fish in British Columbia is a function of historic, repeated, large-scale glacial events that successively swept B.C. clean of its fish fauna. The most recent glacial period (Wisconsin) is believed to have advanced approximately 50,000 BP, and began withdrawing from the Pacific Coast and southern extents nearly 10,000 BP. During the Wisconsin glacial period the majority of British Columbia was covered by the Cordilleran ice sheet and the biota was either destroyed or pushed into ice-free refuges that lay beyond the ice mantles. Evidence suggests that at least two areas along the B.C. coast remained ice free, but the majority of ice-free refuges lay outside B.C. borders (McPhail and Lindsey 1970; Hebda and Haggarty 1997).

The maximum extent of the Wisconsin glacial period saw the Cordilleran ice mantle reach the northern edge of the Columbia Plateau, and several ice-lobes had isolated portions of the Columbia River Basin. These ice dams impounded large portions of the Columbia River into a series of vast lakes that were formed and emptied in a number of catastrophic floods that swept across eastern Washington State (Allen et al. 1986). The recolonization of fish held in refugial areas south of the ice sheets (Columbia Refuge) began about 13,000 BP, with the retreat of the ice mantle in the lower Kootenay region (McPhail and Carveth 1992). By about 11,000 BP the remaining fronts of the Cordilleran ice-sheet began to withdraw, and British Columbia was repopulated by fish species native to the southern Columbia Basin. The Columbia Refuge fish immigrants would eventually spread through a series of ephemeral connections into the upper Fraser, Peace River and Mackenzie River drainages as the slabs of continental ice continued to retreat (McPhail and Lindsey 1970). The historic connections of the Columbia Basin with the Fraser River and Peace River drainages make the fishes of the Columbia Basin the single most important representation of B.C.'s freshwater fish diversity.