Description: Introduced to Lake Superior in the 1980s in the ballast water of a transatlantic ship.
Identification: Green-brown above, many small dark blotches on light brown sides, yellow below and clear to pink pectoral fins. Body is similar shape and size to a perch. Two large dorsal fins joined together; forward fin as spiny rays, rear fin has soft rays. Dorsal and caudal fins have many small black spots. On average between 5 to 10 inches.
Habitat: Prefer lakes or quiet pools and margins of streams. Tolerant to a wide range of ecological and environmental conditions including fresh and brackish waters as well as turbid or polluted waters.
Reproduction: Females can start reproducing at 2 years and males at just 1 year. Ruffe can spawn in a wide range of habitats and temperatures. The eggs hatch in 5 to 12 days.
Impact and Damage: Ruffes compete with native fishes for food and space; they also eat the eggs of native fishes, which can cause a decline in affected populations. Ruffes' ability to reproduce rapidly and adapt to a variety of habitats and environments allow them to quickly dominate an area.
Similar species: Yellow perch (Perca flavescens), Trout-perch (Percopsis omiscomaycus) and Walleye (Stizostedion vitreum), which all can be distinguished by their slightly downturned mouth, large and spiny dorsal fin and lack of scales on their head.
Monitoring and rapid response: Control methods for ruffes include the use of alarm pheromones to exclude them from particular areas, the use of a sex pheromone to assist in trapping them and the use of a sperm antibody to assist in the disruption of the reproductive process. Improved ballast water management and prohibiting transport of ruffes for live bait are also encouraged practices to limit spread. Lampricide use has also been an effective method of eliminating invasive ruffe populations with minimal nontarget mortality.
Credits: The information contained in this factsheet was provided by the Shedd Aquarium.