. The Canadian field-naturalist. 180 The Canadian Field-Naturalist Vol. 105. FlGl ki 1. Rhinichthys falcatus (58 mm SL, UBC 56-573) from Nazko River, Fraser River Drainage. Drawn by Karen Uldall-Ekman. around the caudal peduncle (average 32 to 36 in R. umatilla). Many R. falcatus have white tubercles on the head or near the tip of each scale giving an appearance of there being regular rows of tubercles along the back. Such tubercles were not observed on other species of dace that we studied. Distribution Rhinichthys falcatus inhabits the Columbia and Fraser systems. Distributional records are
. The Canadian field-naturalist. 180 The Canadian Field-Naturalist Vol. 105. FlGl ki 1. Rhinichthys falcatus (58 mm SL, UBC 56-573) from Nazko River, Fraser River Drainage. Drawn by Karen Uldall-Ekman. around the caudal peduncle (average 32 to 36 in R. umatilla). Many R. falcatus have white tubercles on the head or near the tip of each scale giving an appearance of there being regular rows of tubercles along the back. Such tubercles were not observed on other species of dace that we studied. Distribution Rhinichthys falcatus inhabits the Columbia and Fraser systems. Distributional records are indicated in Figures 2 and 3. United Stales Washington, Oregon and Idaho: Rhinichthys falcatus inhabits the main stem of the Columbia drainages including the full length of the Columbia River from its estuary to the Canadian border. This includes lower reaches of the Snake, Willamette, Umatilla, John Day, Malhuer, Clearwater, Payette, Boise, Bruneau and Similka- meen rivers. Simpson and Wallace ( 197X) and Lea ct al. (19X0) describe waterfall barriers { Shoshone Falls, Spokane Falls) which prevent dispersal into upstream portions ol the Columbia Riser Basin. Present day construction ol dams would appear to further restrict genetic inter- change between tributary drainages and prevent natural restocking ol lost populations. I here ate ords from the Cowlitz, Yakima and Walla Walla met systems (records from upstream drainages ol the Deschutes Rivei need 1.' ation). I he Similkameen Rivei population ol Washing- ton ma) in- oi majoi significance to Canadian populations because the species occurs in large numbers immediately below the Canadian bordei ami ma) aet as a genetic reservoii foi immigrants into ( anada(Hughes and Peden l(>xv Peden and Hughes I«>xk) Presently, this population is isolated from downstream populations b) a dam .mil waterfall above Orville, Washington British Columbia Columbia System: Rhinichthys falcatus is known from four areas within the Columbia
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