The lake chub (Couesius plumbeus) is a freshwater cyprinid fish found in Canada and in parts of the United States.

The back is olive-brown or dark brown, and the sides are leaden silver, hence the word plumbeus, referring to lead, in the scientific name of this fish.

The scales are small but well visible, and some may be black and form isolated dark spots on the lower sides.

Some scattered populations are also present in the northern United States, more precisely in New England, Michigan, Iowa, Wisconsin, Minnesota, the Dakotas, Montana, Wyoming, Colorado, Washington, Idaho and Utah.

Its range also includes Lake Michigan in Illinois and the Platte River system in Wyoming.

[3] Migrating chubs leave their lakes and rivers to ascend tributary streams, in which they mate (by day or night) and release their eggs over gravel or rocks.

[3] In the laboratory, lake chubs have expressed free-running circadian rhythms that are among the most precise of the few fish species studied to date.

[8] The lake chub has large optic lobes in its brain and is therefore presumed to be a good sight feeder.

[10] Comparisons with other freshwater fishes such as stickleback, northern pike, sculpin, and burbot have revealed that it has a superior hearing capacity.