Overview
The ruffe (Gymnocephalus cernuus), a small spiny perch capable of explosive population growth, is one of the latest foreign arrivals threatening the Great Lakes fishery. Native to lakes and rivers in Eurasia, the ruffe was introduced to Duluth Harbor on Lake Superior via ballast water of an ocean going vessel and first collected in fish surveys in 1986.
The ruffe competes with native fish for food and habitat. Its ability to displace other species in newly invaded areas is due to its high reproductive rate, its feeding efficiency across a wide range of environmental conditions, and characterstics that may discourage would-be predators such as walleye and pike.
Ruffe grow rapidly and can reproduce in their first year. In the St. Louis River, near Duluth, Minnesota, females can lay between 45,000 and 90,000 eggs a year. Ruffe are primarily bottom feeders, preferring dark environments where they can hide from predators. Ruffe rarely grow bigger than 5 inches, although the sharp spines on their gill covers, dorsal and anal fins make them difficult for larger fish to eat.
Likely means of spread: Ruffe could be accidentally transported in livewells, bilge water, bait buckets, and in the ballast water of Great Lakes freighters.
Eurasian Ruffe Factsheet U.S. Geological Survey (USGS), Great Lakes Science Center Outlines potential impacts of Eurasian Ruffe in the Great Lakes and how it can be controlled.
Gymnocephalus cernuus U.S. Geological Survey (USGS) Nonindigenous occurrences, map, means of introduction, and impact of the Ruffe.
Ruffe (Gymnocephalus cernuus) Sea Grant Nonindigenous Species Site (SGNIS) Includes scientifically reviewed articles as well as images from Sea Grant researchers.
Ruffe Home Page University of Minnesota This page points to ruffe researchers, news articles and more.
Ruffe ID Card Minnesota Sea Grant Program Informative fact sheet on the ruffe, 1998.