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Major goals and objectives: Our three
major objectives are to: (1) determine the potential competitive interactions between
exotic Eurasian ruffe and native yellow perch in Lake Michigan and throughout the Great
Lakes, through new knowledge of their preferences for prey and habitat, (2) determine how
predators (e.g., pike) and another exotic animal, zebra mussels, might affect the success
of ruffe and their interactions with yellow perch in the Great Lakes, and (3) determine
the current composition of benthic macroinvertebrates in Lake Michigan to generate a
baseline prior to the anticipated invasion by ruffe.
Summary of progress: We have completed our
3rd year of research as part of this project, which has been extended for a 4th
and final year with a no-cost extension. This project is a collaborative effort among four
Sea Grant programs (Minnesota, Michigan, Ohio, and Illinois-Indiana) to assess the
potential environmental consequences of the invasion of the Great Lakes by Eurasian ruffe
(Gymnocephalus cernuus). The Illinois-Indiana component of this integrated project
has focused on using laboratory experiments to assess the interactions among ruffe, yellow
perch (Perca flavescens), potential fish predators, and zebra mussels during an
invasion scenario such as might occur in southern Lake Michigan. We have completed the
perch-ruffe competition study (objective 1 above), which has resulted in a published
manuscript in a special issue of the Journal of Great Lakes Research devoted to
ruffe (Fullerton et al. 1998), and we are currently preparing two more manuscripts for
submission (see citations below). We have also conducted ancillary work on round gobies in
Lake Michigan, and have a paper in press (Benning and Berg, in press). We have addressed
objective 2 with laboratory experiments, and a manuscript is being prepared on ruffe
– zebra mussel interactions. We are midway through our experiments on predator-prey
relationships. A field survey of benthic macroinvertebrates in southern Lake Michigan
(objective 3) was repeated in 1998 to establish the baseline prior to ruffe invasion.
Results from the 1997 survey were published in Fullerton et al. 1998.
Accomplishments: This project is providing
basic information relevant to the management of Eurasian ruffe as they extend their range
within Lake Superior and possibly into the other Great Lakes. A paper in a widely read
journal (Journal of Great Lakes Research) has been published and several other
papers are in varying stages of preparation for publication (2 papers should be submitted
before the end of 1998). In 1998, we also presented our results at the annual meeting of
the North American Benthological Society (including within the Presidential Address
by Gary Lamberti) and at the joint meeting of the Ecological Society of America and
American Society of Limnology and Oceanography. An update on our research will be
presented at the forthcoming International Conference on Zebra Mussels and Aquatic
Nuisance Species in Duluth, Minnesota, in April 1999. Our work was also highlighted in
a report by The Science Coalition to the U.S. Congress entitled "Great
Advances in Scientific Discovery" as one of the 162 significant scientific
breakthroughs of 1998 (see attachment). All of these venues provide important information
for management decisions with regard to the ruffe invasion.
Benefits: Many state and federal agencies
are responsible for the management of fisheries and water resources within the Great
Lakes. Nominally, these include the U.S. Fish and Wildlife Service, U.S. Environmental
Protections Agency, Great Lakes Fishery Commission, U.S. Army Corps of Engineers, and the
Departments of Natural Resources or Environmental Management for the various states
bordering the Great Lakes. All of these agencies will be able to use our findings to
better manage Eurasian ruffe in the Great Lakes and their inflowing rivers. Because our
research was highlighted in the report to Congress, this should emphasize the threat of
exotic species at the national level while providing visible benefits to Sea Grant. Our
research has also been highlighted in local news stories, thereby informing the public of
the threats of exotic species. News stories also inform the public of the relevance of our
work and the importance of supporting basic research.
Narrative Report:
Overall Summary: A major issue in the management
of the Eurasian ruffe invasion is whether ruffe will compete with native yellow perch, an
important commercial and sport fishery in lakes Michigan and Erie and an important forage
fish for large predators (e.g., walleye, pike, lake trout). We have found that ruffe will
consume similar food as perch, and share habitat with perch, and thus will potentially
compete with yellow perch where they coexist. Both species, however, suffer from reduced
growth rates when they coexist in laboratory tanks at fairly high densities with limited
food. It is also possible that another exotic species, zebra mussels, will modify habitat
sufficiently to alter the interaction of ruffe and yellow perch. Zebra mussels provide
refuge for invertebrates, thereby making them less accessible to fish. We are also
examining whether large predators (e.g., walleye, northern pike) will feed on ruffe,
thereby slowing invasion rates or using ruffe as an alternate food source. These
experiments are ongoing, but it appears that predators show large individual variation in
their predation on ruffe. The baseline study of Lake Michigan invertebrates continues to
show that prey items suitable for ruffe are abundant in the western and southern portions
of the lake.
Abstracts of Papers in Preparation (see citation below):
INFLUENCE OF HABITAT AND FOOD ON INTERACTIONS OF
EURASIAN RUFFE AND YELLOW PERCH
The exotic Eurasian ruffe (Gymnocephalus cernuus) is
invading areas of the Great Lakes currently occupied by native yellow perch (Perca
flavescens) where they may compete interspecifically for habitat or food resources.
The likelihood of competition for food depends, in part, on whether these fishes overlap
spatially and temporally and on their relative abilities to consume the food types
associated with given habitats. We conducted two sets of laboratory experiments to
quantify habitat (mud, cobble, macrophytes) and food (benthic invertebrates) use. The
first set of experiments examined ruffe and yellow perch habitat preferences, the
influence of fish density and the presence of food on these preferences, and if fishes
competed for habitat space. Ruffe and yellow perch both preferred macrophytes to cobble
and cobble to mud in the light; ruffe increased their use of mud in the dark. Neither fish
density nor the presence of food affected habitat choice, and competition for habitat was
not evident. In the second set of experiments, we quantified the relative abilities of
each fish species to consume invertebrate taxa (chironomids, oligochaetes, and amphipods)
in each of the three habitats. For both fishes, feeding rates were marginally lower in
macrophytes than in cobble and mud. Feeding rates did not differ significantly between
fish species. Although ruffe and yellow perch apparently occupy different habitats in
nature, our experiments suggest that if they are forced to occupy the same habitat (e.g.,
during invasion or because of predation risk), competition for space will be weak, if it
occurs at all. However, competition for food may occur within a shared habitat when
resources are limiting because neither species has a clear advantage in its ability to
consume food taxa in any habitat.
RESOURCE COMPETITION BETWEEN EURASIAN RUFFE AND
YELLOW PERCH
The Eurasian ruffe (Gymnocephalus cernuus), an
exotic percid fish now established in the Great Lakes, is invading areas currently
occupied by native yellow perch (Perca flavescens). We conducted two laboratory
experiments to test whether competition for benthic macroinvertebrate food (the
oligochaete Lumbriculus) may occur, thus resulting in reduced growth of either or
both species. In the first experiment, we compared short-term growth of ruffe and yellow
perch among 6 treatments (1 ruffe or 1 yellow perch alone, 2 ruffe or 2 yellow perch
alone, 1 fish of each species together, and 2 fish of each species together, each
replicated 9 times) at 21 °C over 7 d in 40-L aquaria with mud substrate. Growth was
measured both as change in mass and as RNA levels in white muscle tissue of fish (an index
of short-term growth). We conducted a second, longer-term experiment in 1-m2
tanks at 17 °C for 58 d, using 4 treatments (2 ruffe or 2 yellow perch alone, 1 fish of
each species together, and 2 fish of each species together, each replicated 3 times).
Growth rates of ruffe did not differ from those of yellow perch within a treatment in
either experiment. In both experiments, however, growth of both species was reduced by
about 70% in the high-density treatment (2 ruffe + 2 yellow perch) as compared to
low-density (# 2 fish) treatments. Results of RNA analyses were consistent with change in
mass and represent an alternative approach to assessing growth responses. In
ruffe-yellow
perch interactions in nature, fish density may be more important than species composition
in determining growth rates when food is limiting. Thus, invasions that increase overall
fish density may be detrimental to the growth of both fishes.
International Implications: Range
expansions by ruffe, and their ecological and economic effects, are an international
problem. For example, Canadian provincial and federal agencies, such as the Ministries of
Natural Resources, are involved in addressing and managing the ruffe invasion of the Great
Lakes. The U.S.-Canadian Joint Commission addresses regulatory issues involving shared
lakes and resources. Furthermore, ruffe have invaded most of continental Europe,
Scandinavia, and the British Isles from their origin in the Baltic Sea area, with various
ecological and economic impacts. Thus, ruffe invasions are a global problem and research
on ruffe has global application.
Media coverage: Our research has been
highlighted in a story in the South Bend Tribune, on an internet site of The Science
Coalition (http://www.sciencecoalition.org/), and in a report to Congress (see attached
clippings).
Partnerships with other institutions/individuals:
This project is a unique collaboration among researchers at four Sea Grant programs
(Minnesota, Michigan, Ohio, and Illinois-Indiana) to assess the potential environmental
consequences of the invasion of the Great Lakes by Eurasian ruffe. We are working with
researchers at the University of Minnesota (Duluth and Twin Cities campuses), University
of Michigan, and University of Cincinnati. Other, informal interactions have been
developed with various state and federal agencies, including the Wisconsin Sea Grant
Program, the Biological Resources Division of the U.S.G.S., and the Indiana Department of
Natural Resources.
Publications:
Benning, L.A. and M.B. Berg. In press. Benthic invertebrate
community responses to round goby (Neogobius melanostomus) and zebra mussel (Dreissena
polymorpha) invasion in southern Lake Michigan. Journal of Great Lakes Research.
Fullerton, A.H., G.A. Lamberti, D.M. Lodge, and M.B. Berg.
1998. Prey preferences of Eurasian ruffe and yellow perch: comparison of laboratory
results with composition of Great Lakes benthos. Journal of Great Lakes Research 24:319-328.
Fullerton, A.H., G.A. Lamberti, and D.M. Lodge. In
preparation. Influence of habitat and food on interactions of Eurasian ruffe and yellow
perch. For submission to: Can. J. Fish. Aquat. Sci.
Fullerton, A.H., G.A. Lamberti, D.M. Lodge, and M.B.
Berg. In preparation. Resource competition between Eurasian ruffe and yellow perch. For
submission to: Trans. Am. Fish. Soc.
Fullerton, A.H. 1998. Potential impacts of Eurasian
ruffe on yellow perch and benthic macroinvertebrates in the Great Lakes. M.S. thesis. 130
pp. University of Notre Dame.
Kolar, C.S., K.M. Martin, A.H. Fullerton, G.A. Lambert, and
D.M. Lodge. In preparation. Influence of zebra mussel-covered substrates on the foraging
rates of native yellow perch and exotic Eurasian river ruffe. For submission to: Can.
J. Fish. Aquat. Sci.
Undergraduate/graduate students supported by project: A
total of 8 graduate and undergraduate students were supported by this project in 1997/98.
Students Supported at the University of Notre Dame (total
of 5):
Graduate students: Aimee H. Fullerton - M.S. 1998, Cynthia
S. Kolar - Ph.D. candidate.
Undergraduate students: Kristine Martin, Jennifer Mason,
Barbara Hinsman
Students Supported at Loyola University of Chicago (total
of 3):
Graduate students: Nicole Vidales - M.S. candidate, Nia
Haller - M.S. candidate, Jeffrey Coath - M.S. candidate
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