The common rudd (Scardinius erythrophthalmus) is a bentho-pelagic freshwater fish, widely spread in Europe and central Asia, around the basins of the North, Baltic, Black, Caspian and Aral seas.

[3] It has been artificially introduced to Ireland, United States, Morocco, Madagascar, Norway, Tunisia, New Zealand, Canada, and Spain.

[4] Rudd have been found in the US states of Alabama, Arkansas, Colorado, Connecticut, Georgia, Illinois, Indiana, Kansas, Massachusetts, Maine, Missouri, Nebraska, New Jersey, New York, Oklahoma, Pennsylvania, South Dakota, Texas, Vermont, Virginia, West Virginia, and Wisconsin.

[9] No person, firm, corporation, partnership nor association shall possess, sell, offer for sale, import, bring, release or cause to be brought or imported into the State of Alabama any species of fish "rudd" (Scardinius erythrophthalmus) or "roach" (Rutilus rutilus) nor any hybrids of either species.

[11] It prefers shallow weedy areas in lakes and river backwaters, where mature females lay up to 200,000 eggs on submerged vegetation.

Young rudd eat zooplankton, aquatic insects, and occasionally other small fish.

The rudd can consume up to 40% of their body weight in vegetation per day, as much as 80% of which is discharged as waste, releasing nutrients into the water column.

In the laboratory rudd readily hybridize with the U.S. golden shiner (Notemigonus crysoleucas).