Since the 1800’s, over 136 species of exotic algae, fish, invertebrates, and plants have become established in the Great Lakes. As human activity has increased in the region, particularly with the opening of the St. Lawrence Seaway, the rate of successful introduction of exotic species has surged. More than 1/3 of these invasive organisms were introduced since the 1960s and many now dominate the aquatic community in both numbers and biomass. The most problematic invasive species include alewife, common carp, Eurasian ruffe, Eurasian water milfoil, purple loosestrife, quagga mussel, rainbow smelt, round goby, rusty crayfish, sea lamprey, spiny waterflea, and the zebra mussel. These species alone have contributed to massive extinctions of native fauna, severe alterations in local food webs, and the zebra mussel alone has resulted in millions of dollars of damage to local water users such as municipalities and industries. While many of these exotics have been in the Great Lakes for over a decade, recent increases in disease outbreaks (e.g., botulism and thiamine deficiency syndrome); blue-green algal blooms; loss of key invertebrates such as Diporeia in lakes Michigan, Ontario, and Huron; decline in recruitment and body condition of important native fish such as lake whitefish in Lake Huron; and an expansion of the “dead zone” in Lake Erie, indicate severe ongoing ecosystem oscillations in many parts of the Great Lakes.

Exotic species in the Great Lakes are a concern to other watersheds in North America due to the interconnectivity of these waters through canals, commercial and private boat traffic, and recreational practices. A prime example of rapid expansion from a regional to a national issue can be seen with the invasion of the zebra mussel. Zebra mussels were first introduced into the Great Lakes around 1986. In less than 10 years, they have spread throughout the Great Lakes, into many small inland lakes and rivers in most of the states bordering the Great Lakes, and have moved into the Mississippi River and can be found all the way down to New Orleans. A second exotic species, the round goby, is poised to repeat this invasion pattern. There are also three exotic Asian carp species (bighead, black, and silver) poised to enter the Great Lakes watershed from the Mississippi River.

Once exotics become established, management efforts to limit expansion are generally costly and rarely successful. Prevention is the best management strategy. Targeted research on impact, prevention, and control strategies, and dissemination of this information to managers and resource users in a timely manner is needed. There a numerous other exotic species poised to enter the Great Lakes, and only rigorous prevention programs will prevent further damage to Great Lakes water resources. The Great Lakes Science Center, through its many partnerships with state, tribal, and U.S. and Canadian agencies, is critical to the efforts to increase the region’s understanding of the impact of exotic species.

The Great Lakes Science Center’s exotic species research program is a well-balanced mixture of prevention, control, monitoring, and impact studies that vary in geographic scale and complexity depending on the species, region, and resource need. However, much of the research is integrated into ongoing Status and Trends or Fisheries programs, or through the Sea Lamprey program; very few studies are funded directly through the Invasive Species Program. The Center’s sea lamprey program, based at Hammond Bay, is unique in its structure and function. This is the oldest collaborative exotic species program in the Great Lakes and is also the only one that deals with eradication, as well as population monitoring and basic biology. Through substantial efforts of all partners, sea lamprey populations have been drastically reduced throughout the Great Lakes. This program is discussed in detail separately.

Research on other exotic species is more regionally based and tends to focus on basic information rather than eradication. The problem facing this research program is the large number of new invaders that have become established over the past 5-15 years, and species continue to be introduced. During the early years of an invasion, resource managers, user groups, and regulatory agencies need data on geographic distribution, population dynamics, basic biology, and predicted impact on native communities. The Center’s long-term deep-water data sets have been instrumental in providing this key information on new invaders across much of the Great Lakes. This research is funded primarily under Status and Trends or Fisheries programs. As needed, additional research studies have been undertaken to address specific resource questions. This included work on population dynamics of European ruffe in Lake Superior, use of soft sediments as habitat by dreissenids in lakes Erie and Ontario, characterizing the “dead zone” in Lake Erie, displacement of native benthic fish from spawning grounds by round gobies, predation on lake sturgeon eggs by round gobies, competitive interactions between different exotic species, and movement of round gobies and dreissenids into deeper waters of Lakes Michigan and Huron. Some of this research has been funded through the Invasive Species Program; most have been funded through outside funding sources.

The Center has also provided critical research to support the control and prevention of exotic fish and invertebrates, though not to the degree seen with sea lamprey. Center biologists were instrumental in testing the electric barrier installed in the Illinois Waterway canal system to prevent movement of round gobies from the Great Lakes into the Mississippi River drainage. Research has also investigated the impact of zebra mussels on native unionids in enhanced or native refugia. Center biologists also assist partners such as the National Park Service in developing and implementing aquatic exotic species prevention programs, serve on national and international panels, and participate in regional, national, and international workshops.

Through its partnerships and research capabilities, the GLSC is well positioned to continue to play an important role in exotic species research. This must remain a multi-layered, multi-disciplined program due to the fact that exotic species continue to enter and become established in the Great Lakes. Great Lakes managers and resource users will continue to need information on all aspects of new and existing exotic species, including basic biology, geographic distribution, and potential impact on existing biota. However, the ability to respond effectively to exotic species would be enhanced if the Center’s research contained both proactive and ecosystem process components.

A proactive approach to exotic species would require development of predictive models capable of forecasting the next likely invader, vectors of invasion, primary points of entry, probable geographic spread, and risk to the existing community. Such a modeling program would enable strategies to be developed for research, containment and control, refugia for native species, etc., before the arrival of the next invader rather than after. The Center’s extensive network with state, federal, Canadian, and tribal entities will enhance the efficacy of this type of program. At current funding and staffing levels, a proactive status will be difficult to achieve since the Center must continue to provide the basic information on current and new exotic species as needed by the regional resource managers and users.

More research into ecosystem processes and linkages is needed if the Center is to provide accurate information on the impact of an exotic species once it becomes established in the Great Lakes, particularly those occupying lower trophic levels. To date, the major portion of the Center’s invasive species work has been a sideline of ongoing community status and trends research, which is usually regionally limited and/or focused on response of top predator fish stocks or changes in prey fish. This research focus provides sufficient data for changes in the top fish community and their prey fish, but not data on other changes in the lower trophic levels. GLSC is best situated to provide data on deepwater/nearshore ecosystem linkages and the changes brought about by the continued invasion of exotic species across all trophic levels. Additions to the long-term status and trends work will provide substantial information of critical need to the Great Lakes community. Such integrated ecosystem research is already ongoing in Lake Ontario and is proposed for other areas.

Continuing invasions of exotic species heightens the need for the development of better tools than what currently exists for preventing, controlling, and mitigating the impact these invasives have on the Great Lakes. A prime example of technology innovation and development is the work on non-chemical control of sea lamprey. The Center’s work on the electric barrier in the Illinois Waterway canal system is also a good example of the type of cooperative effort in technology and partnerships needed to minimize inland spread. However, additional techniques are needed to prevent the initial establishment of invasive species. Further work in this area is critical for the continued survival of native fish and invertebrate communities within the Great Lakes.

For more information on exotic species in your area, please refer to the Nonindigenous Aquatic Species Program hosted by the Eastern Region of the US Geological Survey.