ruffe

The ruffe (Gymnocephalus cernua) is a freshwater fish in the perch family Percidae. It is native to Europe and parts of Asia and is also known as the common ruffe or Eurasian ruffe. In North America it is notable as an invasive species that established in the Great Lakes basin in the late 20th century.

Description: The ruffe has an elongated, laterally compressed body with two dorsal fins; the first dorsal fin has spines and the second is soft-rayed. It typically grows to about 12–25 cm, with a maximum around 30 cm. Coloration is variable, usually brown or olive with dark vertical bars; juveniles are often more silvery. The mouth is moderately protractile, adapted for bottom feeding.

Habitat and biology: It inhabits lakes, rivers, and reservoirs with clear to moderately turbid water, often on sandy, muddy, or vegetated bottoms. It is a generalist feeder: juveniles feed on zooplankton, while adults consume invertebrates and small fish, and may shift toward plant material or detritus at times.

Ecology and invasiveness in North America: As an introduced species, the ruffe competes with native fishes for food and habitat and can disrupt local food webs, particularly affecting small native fishes and ichthyoplankton. Its cold-water tolerance and relatively high reproductive rate have aided rapid expansion through the Great Lakes and connected systems.

Reproduction: Spawning occurs in spring and early summer; females lay adhesive eggs that attach to vegetation, debris, or substrate. Maturity is typically reached within one to two years, and lifespans can extend a few years in favorable conditions.

Management: Monitoring and prevention of further spread are primary management strategies, as effective eradication in natural systems is challenging.