Overview of the International Symposium on Eurasian Ruffe ( Gymnocephalus cernuus) Biology, Impacts, and Control

Abstract

This special topic section is dedicated to ruffe (Gymnocephalus cernuus), a small but aggressive fish native to Europe and Asia. Ruffe were introduced into the St. Louis River, the largest U. S. tributary to Lake Superior, in the early 1980s, probably in the freshwater ballast of ocean-going vessels. The port of Duluth-Superior is located in the St. Louis River estuary in western Lake Superior, and is the largest inland port in the United States. At the time of their discovery in 1987, the available literature suggested that ruffe mature quickly, have a high reproductive capacity, spawn over an extended period, and adapt to a wide variety of environments. This potential for rapid population growth, coupled with the threat of competition for food and space with native fishes, and predation on their eggs (Ogle, this volume), was perceived to pose a serious threat to fisheries in the Great Lakes as well as across North America. True to those early predictions, ruffe became the most abundant fish (based on trawl samples) in the 13,000-acre St. Louis River estuary within 5 years (Bronte et al., this volume). They quickly spread on their own nearly 200 miles along the south shore of Lake Superior by 1994. Ruffe were found in Thunder Bay, Ontario in Canadian waters of Lake Superior in 1991 and in Thunder Bay, Lake Huron (near Alpena, Michigan) in 1995, most likely having been transported via ballast water of ships leaving the Port of DuluthSuperior. Populations at both these locations are small but appear to be reproducing. The International Symposium on the Biology and Management of Ruffe was organized to address the potential threats ruffe pose to North American fisheries. Scientists in diverse disciplines from Eurasia and North America were brought together in an attempt to examine all aspects of the North American invasion of ruffe, and to highlight the effects of similar introductions in Europe and Asia.