Cleaning up the Great Lakes The Voice (7/30) New standards governing the cleaning of ballast water in ocean-going freighters, about to be adopted by the U.S. Coast Guard, should help prevent release of non-native species into the Great Lakes and other threatened U.S. waters.
Luring an invasive fish with pheromones Great Lakes Radio Consortium (1/3) The discovery of a chemical compound that attracts an invasive fish could be a breakthrough in controlling harmful fish populations.
Threat increasing from invasive fish Great Lakes Radio Consortium (9/9) A spiny fish that can hunt in the dark has invaded Lake Michigan. The foreign fish is known as the Eurasian ruffe.
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.