A few comments. Someone mentioned temperments. In my experience Western Blacknose Dace are more aggressive than Eastern. As for different face shapes. Rhinicthys seem to do that. One population of Blacknose Dace me and Mike found had a more sloped body and pointy face that looked almost Longnose like.
The western Nooksack subspecies of Longnose dace has a more bulgy snout than the other varieties, etc.