The report presents the content of presentations and discussions held over 2 1/2 days in a plenary session and in working groups at the Environmental Protection Agency's Introduced Species Workshop held in Saginaw, Michigan on Sept. 26-28, 1990. The purpose of the workshop was to review and evaluate existing information on the ecology and management of introduced aquatic nuisance species, with a particular emphasis on the zebra mussel (Dreissena polymorpha), and make recommendations on how to extend our knowledge and understanding in critical areas. Speakers were asked to provide extended abstracts of their presentations, which are included here in Appendix A. Two of the speakers, from the Soviet Union, submitted their entire manuscripts. The discussions from each working group are presented in the relevant sections. Recommendations are presented in the introductory section.

Shipping list no.: 91-0327-P. "EPA/600/3-91/003." "December, 1990." "February 1991." Includes bibliographical references.

Introduction and summary -- Ecological effects of the zebra mussel -- Rate and extent of spread of the zebra mussel -- Control of established species -- Prevention of new introductions -- Appendices. Zebra mussels (Dreissena polymorpha) are a new invading species in North America with such an enormous feeding and reproductive capacity that they are spreading in epidemic fashion throughout the Great Lakes. Although the mussels are of immediate economic concern because they clog water intake pipes, the greatest concern is the possibility of catastrophic changes in the ecology of the Great Lakes. Zebra mussels can strongly outcompete other indigenous benthic organisms in many temperate aquatic habitats. The success of this mussel will have severe and dramatic consequences on the ecological integrity of surface waters due to major shifts in trophic interactions, the movement of nutrients and toxic materials, and competition with native species.