The fish assemblage of the Canadian River in Texas historically was dominat
ed by Hybognathus placitus and Notropis girardi. These species represented
> 90% of fishes collected from the Canadian River in 1954-1955. Constructio
n of two reservoirs on the Canadian River in the 1960s (Ute Reservoir, New
Mexico, 1962; Lake Meredith, Texas, 1965) altered hydrologic conditions in
the river and affected the fish assemblage. Downstream from Ute Reservoir,
mean annual discharge decreased by about 38% after impoundment, but N. plac
itus, N. girardi, and other mainstem species still dominate the assemblage.
Downstream from Lake Meredith, mean annual discharge decreased by 76% and
the historic mainstem fish assemblage has been almost completely replaced b
y species that formerly were restricted to tributary streams. The magnitude
of post-impoundment changes in the fish assemblage of the Canadian River a
ppears to be related to the degree that discharge has declined, especially
during the spawning season.