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CENTER FOR AQUATIC ECOLOGY

Public Service

The primary activity of Center scientists is to conduct original scientific research. Their findings are disseminated in a number of ways, including publishing them in a variety of quality peer-reviewed journals. Presentation to peers at scientific conferences represents an additional and timely avenue. This past year, Center scientists delivered 16 departmental seminars at a variety of universities within and outside the country and made over 47 scientific presentations at international, national, regional, and state conferences. In addition, two Center scientists organized major symposia: Dr. Richard E. Sparks helped organize the International Water Resource Association's "River Tech 96," and Dr. David P. Philipp helped organize a symposium at the 1996 Midwest Fish and Wildlife Conference entitled "The Role of Reproduction in the Management of Centrarchids." Center scientists also recognize the importance of providing information directly to the citizens of Illinois, including presentations to many local/state nature clubs, fishing groups, governmental organizations, and so forth. Finally, Center scientists also provide timely findings to the governmental agencies that are funding specific research projects; over 30 technical reports were submitted this year alone.

The Center for Aquatic Ecology (CAE) is extraordinarily active in conducting research. This high level of activity is made possible by research grants and contracts sought and obtained by individual Center scientists. Once again, all senior staff scientists in CAE had extramural funding to support last year's research efforts; a total of over 50 separate projects were funded in 1996. Support for these projects, totaling almost $4 million, was obtained from a number of state and federal sources (e.g., National Science Foundation, National Biological Service, U.S. Fish and Wildlife Service, U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, Illinois Department of Transportation, Illinois Environmental Protection Trust Fund, Illinois-Indiana Sea Grant Program, and the Illinois, Minnesota, Wisconsin, Iowa, Colorado, and Ontario Departments of Natural Resources).

A second major activity of Center scientists is participation in graduate education. All Center scientists are affiliated with academic departments in at least one major university within Illinois, including the University of Illinois, Eastern Illinois University, Western Illinois University, Northwestern University, and Loyola University. During this past year's academic semesters, Center scientists taught five full lecture courses and supervised two graduate seminars. In addition, Center scientists supervised 4 postdoctoral associates, 27 graduate students (9 Ph.D. and 18 M.S.), and over 50 undergraduate research projects.

A third activity of Center scientists is to serve in an advisory capacity to local, state, and federal agencies as well as nongovernmental and professional organizations. Once again, Center scientists actively participated at all levels. The following are highlights of the past year's activities. Dr. William J. Resetarits served as a member of the National Science Foundation's Special Advisory Panel for Postdoctoral Research Fellowships in the Biological Sciences. Dr. J. Ellen Marsden advised the Great Lakes scientific community at a number of levels, including serving on several of the Lake Michigan Technical Committees and on the Great Lakes Fisheries Commission's Panel on Nonindigenous Aquatic Nuisance Species. Dr. Sparks served at several levels as an advisor to The Nature Conservancy. Drs. Daniel W. Schneider and Sparks served on the Lieutenant Governor's Illinois River Task Force. Dr. Schneider also served on the City of Champaign's Environmental Advisory Commission. Dr. Sparks presented information at the congressional hearings concerning the National Invasive Species Act and participated in a review panel (convened by the United Nations, World Bank, and InterAmerican Developmental Bank) to investigate the environmental impacts of the proposed Parana-Paraguay Waterway Project. Center scientists were also active in federal endangered species recovery activities: Dr. Philipp served on the Colorado River Endangered Fishes Recovery Program's Genetics Panel, and Dr. Daniel A. Soluk served as a member of the Endangered Species Recovery Team for the Hine's emerald dragonfly.

Special Recognition

The Center for Aquatic Ecology wishes to recognize staff efforts expended in editing two recently published books, both reporting the content of exceptional symposia. First, Dr. William Resetarits organized a special symposium, "The State of Experimental Ecology: Questions, Levels and Approaches," at the 1995 annual meeting of the American Society of Zoologists. Results of this very interesting meeting were discussed in several issues of Science. Together with Dr. Joe Bernardo, Dr. Resetarits has assembled 24 papers from that symposium in an important volume entitled Experimental Ecology: Issues and Perspectives published by Oxford University Press. This volume will serve as a historical benchmark of the state of experimental ecology as we enter the next century. Second, a number of current and former scientists from the Center were instrumental in helping to organize the first World Fisheries Congress held in Athens, Greece. Dr. David Philipp served on the steering committee from its inception, and Drs. John Epifanio and Ellen Marsden, with Dale Burkett and Julie Claussen, put together and facilitated four days of sessions that made up one of the six major themes of the Congress, "Protection of Aquatic Biodiversity." As a product of that effort, 22 papers were recently published in a single volume edited by David P. Philipp, John M. Epifanio, J. Ellen Marsden, Julie E. Claussen, and Robert J. Wolotira entitled The Protection of Aquatic Biodiversity. This international volume, containing chapters written by authors from 13 different countries, represents a major synthesis of ideas on this important topic and the culmination of efforts begun in 1985 within the American Fisheries Society. It is through such efforts that the Center for Aquatic Ecology is helping to shape the way the world's scientists are viewing and approaching key ecological issues.

Conservation Biology

Genetics of sport fish in the upper Midwest
R. Fields, M. Desjardins, T. Kassler, J. Ludden, M. Hudson, V. Tranquilli, D. Philipp, M. Jennings, M. Staggs (Wisconsin Department of Natural Resources), P. Wingate (Michigan Department of Natural Resources), C. Toline (Utah State University)
Species of fish are composed of genetically distinct populations uniquely adapted to their environments. To identify individual stocks of sport fishes, researchers are analyzing popu-lations of 12 species of fish from watersheds in the upper Midwest. Protein electrophoresis, RFLP analysis of mitochondrial DNA, and RAPD DNA analysis were used to assess the genetic variation present within and among populations of each species. The variation that was identified has been used to define biologically relevant conservation management units.

Population model for native mussels
D. Blodgett, J. Stoeckel, S. Whitney, R. Sparks
Native mussels are ecologically important components of large floodplain river ecosystems and are economically valuable as raw material for the cultured pearl industry. However, their management has been hampered by an inability to quantitatively assess impacts of natural and anthropomorphic stresses, such as natural and harvest mortality, on their populations. Using Stella II software on a personal computer, researchers are developing a dynamic, single-species population model for mussels that will allow us to combine data from current populations (densities, growth and mortality rates, etc.) with knowledge of their effects on population dynamics to predict future conditions under various management scenarios.

Diapausing eggs in plankton communities
C. Cáceres, A. Tessier (Michigan State University)
Plankton populations can be largely annual or perennial, and variation exists both within and between species. The pattern found in any particular lake is related to both biotic and abiotic features of the system. Quantifying the role of dormancy across populations is critical because the dormant eggs can be quite long-lived, and therefore can significantly affect the outcome of community interactions as well as the dynamics of individual species. This research seeks to ascertain the functional role of diapausing stages in zooplankton population dynamics in a variety of ecosystems, and how variation in this benthic-pelagic link affects the remainder of the planktonic community.

Trophic interactions in ecosystems
R. Herendeen
Trophic cascade and top-down:bottom-up hypotheses are used to describe and predict how perturbing one organism affects the others in an ecosystem. A quantitative general theory was developed that predicts all features of trophic cascades and top-down:bottom-up effects, and covers intermediate cases as well. Specific quantitative predictions agree with known results from the Lotka-Volterra theory of predator-prey relations. This method, however, is based on comparison of systems at steady state, yet most experimental and real ecosystems are in continual dynamic change. The theory is being extended to include dynamic systems, and testing against recently available data.

Dormancy in Oneida Lake Daphnia
C. Cáceres
Many populations of freshwater zooplankton produce long-lived diapausing eggs that accumulate in lake sediments. In Oneida Lake, New York, the eggs of two species of Daphnia reach densities of over 10⁴ eggs/m². Sedimentation rates obtained by ²¹⁰Pb dating suggest that these eggs can remain viable for over 125 years and that these two Daphnia populations have persisted in this system for over 200 years. Although the two species reach similar population densities in the water column, fewer D. galeata mendotae females switch to the production of dormant eggs than do D. pulicaria. This results in fewer diapausing eggs being produced and stored by D. galeata mendotae, and lower emergence rates.

Developmental genetics of sunfish hybrids
R. Fields, M. Fields, J. Claussen, D. Philipp, J. Epifanio (Michigan State University)
Among the sunfishes, hybridization between species is a common event. This work studies the pattern of gene expression during the various stages of embryonic and larval development of hybrids. Bluegill, pumpkinseed, and their hybrids were collected and gametes from each extracted and used for in vitro fertilizations to make F1 hybrids as well as the backcrosses of each species. Embryos were raised and sampled at various developmental stages. Using molecular techniques, researchers are determining when certain genes turn on during development and the patterns of inheritance of nuclear DNA markers.

Host-parasite relationships in streams
S. Kohler, M. Wiley (University of Michigan)
The effects of parasites and pathogens on the population dynamics of stream invertebrates and the organization of stream communities has received little study. Research indicates that by suppressing the abundance of key species, pathogens can significantly affect structure and energy flow in food webs. Current research focuses on effects of pathogens on the populations of several species representing three distinct trophic groups that are thought to interact strongly with other members of stream food webs. Results suggest that pathogens play an important role in the long-term dynamics of at least three species. Future work will attempt to evaluate the ramifications of such effects for other community members.

Structure of stream food webs
S. Kohler, M. Wiley (University of Michigan)
The resilience of ecosystems to major perturbations and the mechanisms determining the biodiversity of communities are fundamental issues in basic and applied ecology. The removal of a dominant competitor from streams over a broad geographic area by a parasitic infection has provided researchers with a unique opportunity to address these issues in otherwise relatively unperturbed systems. Research focuses on how the dominant competitor affects community organization and energy flow, and how the system responds to the competitor's removal and, perhaps, to its eventual recovery to pre-infection levels.

Brook trout-spring salamander interactions
W. Resetarits
The broad coexistence of stream-dwelling salamanders with predatory fish is a perplexing question in light of the almost total exclusion of pond-dwelling salamanders by predatory fish. This project focuses specifically on the interactions between spring salamanders and brook trout. The goal of this project is to determine (and quantify) the specific factors that contribute to the maintenance and dynamics of spring salamander populations in streams containing brook trout, and to use this as a model system for studying complex mechanisms of species coexistence under asymmetric competition.

Long-term changes in insect communities
S. Kohler, D. Soluk
Data on long-term trends for insect populations in Illinois streams are generally lacking. This is unfortunate because aquatic insects are often excellent indicators of stream quality. Researchers are revisiting a number of streams in the state that were intensively studied by Survey taxonomists in the first half of the century, and for which the mayfly and caddisfly faunas present during that period are quite well known. Because these groups are sensitive to changes in environmental quality, this study should help to determine if and how the integrity of these streams has changed over the past 40-50 years.

Amphibian species diversity
W. Resetarits, J. Fauth (College of Charleston)
An important goal of ecology is identifying and understanding the processes that generate and maintain species diversity. Understanding these processes is also critical to the preservation of biodiversity. Work continues on processes affecting frog species diversity in seasonal wetlands in the Sandhills and Coastal Plain regions of the Southeast. These natural wetlands support the most diverse local assemblages of frogs outside the tropics. Experiments in artificial ponds, field sampling, and field experiments are being combined to develop and test an explanatory model of frog species diversity in these seasonal wetlands.

Upstream movements of invertebrates
D. Soluk, S. Kohler
Knowledge of movement patterns and dispersal mechanisms is needed to understand the dynamics of natural populations and to predict the recovery of communities from the effects of natural or human disturbance. Research on dispersal in streams has focused mostly on drift and predicts that over the season, upstream areas should be depleted of organisms. Lack of evidence of depletion is explained as a function of recruitment from hyporheic or other areas. An alternative explanation is that organisms simply may travel upstream after drifting downstream for some time. Using innovative technology, researchers are measuring upstream movement and colonization under natural conditions.

Local adaptation in largemouth bass
D. Philipp, J. Claussen
When foreign genes are introduced into a native population and interbreeding occurs among individuals, the genetic makeup of that population is disrupted. To assess these potential negative impacts, a series of experiments was conducted to compare survival, growth, and reproductive success of genetically defined stocks of largemouth bass in different geographic habitats. Survival, growth, and reproductive success of the local stocks were superior to those of the introduced stocks. Also, extensive introgression among stocks occurred within a very few generations and the fitness of introgressed individuals was poorer than for individuals in the pure local stock.

Oviposition site choice
W. Resetarits
Many processes may affect the structure and species composition of aquatic communities. One of the least understood is the role of oviposition site choice in the colonization of aquatic habitats. A large component of the fauna in many aquatic systems is the result of repeated colonization by aquatic insects and amphibians; thus, selectivity by ovipositing females has the potential to dramatically affect the structure and function of aquatic communities. Both experimental studies and mathematical modeling are being used to study the role of oviposition site choice in aquatic systems.

Status of the Illinois chorus frog
J. Tucker, D. Philipp, G. Packard (Colorado State University)
The purpose of the study is to gather information necessary to allow successful mitigation of chorus frog habitat loss due to construction of Interstate 255 in Madison County. Researchers' main goals are to estimate reproductive success and population size in the area. Experimental work is also being conducted on freeze tolerance in the Illinois chorus frog. Data indicates that this frog is not freeze-tolerant although other congeners are. Currently, field studies are being conducted to examine actual temperatures experienced by the frogs during winters in central Illinois.

Red-eared slider reproductive ecology
J. Tucker, F. Janzen (Iowa State University)
The primary focus is on annual and seasonal variation in reproduction in relation to flooding on the lower Illinois River. Hatchling research includes experimental release of about 2,000 hatchling sliders. The project examines the impact of predation on recruitment and phenotypes of sliders by replicate releases. Treatments include an undisturbed replicate and one where predators are actively excluded. This study is designed to examine environmental cues used by overwintering hatchling sliders to time their emergence from nests in the spring after overwintering. Researchers are also examining egg size variation associated with oviductal position in the red-eared slider turtle. Various optimal propagule theories will be tested during the study.

Growth in slider turtles
J. Tucker, D. Moll (Southwest Missouri State University), E. Moll (Eastern Illinois University)
Growth patterns among sliders from west-central Illinois are being studied to allow comparisons with studies of growth in sliders inhabiting tropical regions. Studies of sliders from Belize, Costa Rica, and Panama are being or have been completed. These studies will allow us to examine whether growing-season length is the primary cause of differences in growth patterns known to exist among these slider populations.

Dragonfly mortality from motor vehicles
D. Zercher, D. Soluk
Adult dragonflies may be more vulnerable than other insects to impacts caused by roadways near wetlands due to their mobility, longer adult life spans, and lower fecundity. Little research has been done on the population effects of dragonfly roadkill. This information is necessary to determine the possible detrimental impact vehicle collisions may have on dragonfly populations. This research will determine if there is a negative impact on dragonfly populations, which species are most affected by vehicle collisions, and which characteristics make these species vulnerable (e.g., flight heights and speed). This information may be useful when considering road construction near wetland areas.

Sportfishing in Lake Michigan
W. Brofka, J.E. Marsden
Researchers surveyed sportfishing in the Illinois portion of Lake Michigan. The intent of the survey was to provide reliable estimates of sportfishing activity, sport fish harvest, expenditures for sportfishing, and the quality and distribution of sportfishing. Estimated total fishing effort for pedestrians and boaters was 739,000 angler-hours. Estimated total harvest included 389,400 yellow perch; 2,600 brown trout; 5,400 rainbow trout; 2,600 lake trout; 50,000 coho salmon; and 7,100 chinook salmon. Estimated expenditures for boats, motors, trailers, fishing gear, and automobile gas were $9.1 million. The yield value of the sportfishing harvest was approximately $1.66 million.

Effects that determine larval fish growth
R. Claramunt, D. Wahl
Researchers are evaluating the role of several environmental factors that determine the growth of several larval fish species. Sampling was conducted using push nets in inshore and offshore habitats in 21 Illinois reservoirs. Larval sunfish (Lepomis spp.), crappie (Pomo-xis spp.), gizzard shad (Dorosoma cepe-dianum), and minnows (Cyprinidae) were collected from May through July. Lakes were classified based on orphometric and limnological variables and compared to larval fish growth rates. Latitude, lake temperature, and characteristics of zooplankton populations appear to be most highly correlated with growth. The relative importance of abiotic and biotic factors to growth may vary with fish species and habitat.

Species richness and productivity
S. Callahan, D.Wahl
A number of studies indicate that productivity of a system controls diversity. On a regional scale a maximum is reached at intermediate productivity. Few studies have examined these issues in freshwater systems or examined the alternative potential role of species diversity on system productivity and functioning. Two recent terrestrial studies support the hypothesis of species diversity affecting systemwide functions (e.g., nutrient sequestering, carbon dioxide flux). Current freshwater fish management promotes single-species strategies with little regard for fish diversity. Researchers are currently examining relationships between diversity and productivity in ponds with varying numbers of fish species.

Effects of electrofishing on bluegill feeding
S. Callahan, D.Wahl
Researchers evaluated the indirect effects of electroshock on bluegill (Lepomis macrochirus). Feeding rates of large (150 mm) and small (50 mm) bluegill were significantly reduced for up to 6 hours after shock, but were back to the levels of unshocked fish by 12 hours after shock. Small bluegill were more susceptible to predation immediately after shock than were unshocked fish. Within 10 minutes, however, the shocked bluegill were no more susceptible than their unshocked counterparts. The results suggest that there are no long-term indirect effects on bluegill feeding and susceptibility to predation.

Plankton dynamics in river floodplains
J. Goodrich, J. Dettmers, D. Soluk, D. Wahl
Although off-channel (floodplains, backwaters, and side channels) habitats in large river-floodplain ecosystems are recognized as being important to the riverine plankton community, the role they play in structuring this community is poorly understood. Off-channel habitats can be important nursery grounds for larval and juvenile fishes. Furthermore, these habitats are often thought to be a source of zooplankton and phytoplankton for the main river channel. INHS researchers have initiated a study of the Illinois and Mississippi rivers to examine how the plankton community differs and to quantify the biotic fluxes of plankton among habitat types.

Evaluation of Illinois creel survey
T. Edison, D. Austen, D. Wahl
Creel data can be used to determine fishing pressure, angler preference, and population size structure of sport fish species in a lake. Since 1987 various harvest regulations have changed and their effectiveness can be evaluated through creel data. For example, harvest limits have gone from unlimited to a limit of 15 fish in various lakes for crappie. Analysis of creel data can be used to identify changes in size structure within these lakes. These analyses will allow evaluation of the success of harvest limits and show whether management goals were achieved.

Individual-based modeling of walleyes
T. Galarowicz, R. Herendeen, D.Wahl
Overall survival of walleye to fishable sizes depends strongly on the condition of juveniles at the end of the first growing season. Several processes that determine a larval fish's first-summer survival and growth are known to be size dependent, such as susceptibility to predation. Predicting the numbers and condition of surviving juveniles therefore requires a highly disaggregated modeling approach that keeps track of many different size classes. Researchers are building such an individual-based model to better predict the consequences of management options on populations, calibrating it with results from laboratory and field experiments at the INHS Kaskaskia Field Station.

Spawning dynamics of bluegill
J. Claussen, D. Philipp
This long-term study has monitored the annual variation in the number of males that build nests, spawn, and successfully raise a brood off the nest in a 2-km study area of Lake Opinicon, Ontario. Yearly comparisons will determine how environmental changes, such as temperature, affect the variation in the number of breeding males and females in the population as well as how changes in the overall breeding population affect clutch size. These data are providing information needed for modeling bluegill population dynamics in the Midwest that will aid in the production of successful management programs for this important species.

Aquaculture of walleye
T. Galarowicz, D. Wahl
Walleye are popular as food and sport fish throughout the country, but commercial harvesting is not allowed in the U.S. As a result, there is an increased interest in culturing walleye to market size to meet this demand. In response, the North Central Regional Aquaculture Center, a multi-research institute organization that includes the Illinois Natural History Survey, has focused on developing techniques for commercial culture of walleye while evaluating growth, feed efficiency, and stress response under various culture conditions. Researchers from INHS will use a bioenergetics model to study these different components affecting culture success.

Lake trout reproduction in Lake Michigan
M. Chotkowski , J.E. Marsden
Stocked lake trout have failed to reproduce in Lake Michigan and other Great Lakes. In previous years, Survey scientists found evidence that more spawning occurs on man-made structures (breakwalls) than on natural reefs, but fry survival appears to be extremely low. Researchers are currently examining factors that may affect egg and fry survival, focusing on the effect of predation by native and introduced fish species: sculpins, gobies, carp, and alewife.

Lake chubsuckers as forage
R. Eberts, V. Santucci, Jr., D.Wahl
Young bluegills are the principal forage fish in most small impoundments. However, in our area and other northern waters, piscivorous (fish eating) game species, such as largemouth bass, walleyes, northern pike, and muskellunge, grow slowly when bluegills are the only fish species available as prey. Also, bluegills often overpopulate and become stunted, which usually leads to an eventual decline in the reproductive success of piscivorous species. The purpose of this project is to evaluate lake chubsuckers as an alternate or supplemental forage fish for small impoundments.

Estimating fish abundance
R. Herendeen, P. Bayley (Oregon State University)
Size (and therefore age) distribution of fish shows their reproductive health. Determining the distribution from net-capture data is subject to bias because of larger fishes' higher ability to evade the research net. Researchers have explicitly modeled the size-dependent evasion process during the setting-out of a purse seine. This allows us to convert the observed size distribution in the purse seine to the actual distribution. Model results agree qualitatively with observation; scientists continue to calibrate the model with field data (in which a larger, impenetrable block net is used to determine what fish are actually present).

Effects of macroinvertebrates on bass
J. Kline, D. Wahl
Gizzard shad (Dorosoma cepedianum) have been shown to have a major effect on trophic interactions in reservoirs and may influence macroinvertebrate populations. The resulting macroinvertebrate community may, in turn, affect growth rates of young-of-the-year (YOY) largemouth bass (Micropterus salmoides) prior to the switch to piscivory. Researchers are evaluating the role of macroinvertebrates in influencing the growth of largemouth bass by sampling in six Illinois reservoirs, three of which are gizzard shad dominated and three are bluegill (Lepomis macrochirus) dominated. Results will help clarify the role of macroinvertebrate and fish community interactions in influencing the growth of YOY largemouth bass.

Creel surveys on Illinois impoundments
P.J. Perea, B. Carroll, J. Machung, D. Philipp, P. Bayley (Oregon State University), D. Austen and S. Sobaski (Illinois Department of Natural Resources)
Since 1987, INHS scientists have conducted angler surveys of 68 state-managed lakes to estimate the total fishing effort; the species, numbers, and weight of fish harvested and released; and the species targeted by anglers at these lakes annually. The collected data are directly useful to the fisheries management of these lakes, especially in evaluating the effects of short-term management changes and supplemental stocking on yield and catch per angling effort and the impact of sportfishing intensity on the resource.

Evaluation of walleye stocking program
J. Hoxmeier, D. Wahl
Success of walleye, Stizostedion vitreum, stocking is highly variable, and reasons for successes are not well understood. Factors influencing stocking success may include prey availability, predation, or abiotic factors such as water temperature. Prey availability and predation are highly dependent on the size of the walleye. The current study is examining 11 lakes across Illinois to understand factors causing differences in growth and survival among stocked walleye fry as well as small and large fingerlings. These results will be used to develop management strategies that optimize stocking of these important sport fish.

Walleye foraging, growth, and survival
C. Kolar, D. Wahl
Although juvenile walleye are stocked extensively throughout most of the U.S., not much is known about the mechanisms controlling their growth and survival. As a result, the success of walleye stockings has varied considerably. Researchers are evaluating the importance of prey base to juvenile walleye growth and survival in laboratory and pond experiments. Differences in prey morphology and behavior will likely impact juvenile walleye success. Fisheries managers stocking juvenile walleye will be able to use this information to select, based on the prey base, which reservoirs will enhance the success of the stocked walleye.

Spawning of large- and smallmouth bass
D. Philipp, F. Phelan (Queen's University Biological Station), C.A. Toline (Utah State University)
The annual spawning histories (location, date, mating success, and reproductive success) of all male smallmouth bass in a 1.5-km section of a stream and of all male largemouth bass in an 87-acre lake in southern Ontario are being monitored. From individual mark and recapture data, preliminary results indicate that in subsequent years successful males return to previous spawning sites (within 3-4 m), whereas unsuccessful males may move up to 0.5 km. Determining the factors that affect individual variation in male reproductive success will help develop better management programs for these species.

Factors affecting bluegill population size
J. Hoxmeier, J. Claussen, D. Philipp, D. Wahl
Factors that control bluegill population size structure include growth rate, life span, and age at maturation. Stunted bluegill populations can result from overharvest, density dependent growth limitations, large portions of the population maturing at early ages, or from an overabundance of cuckolders. Researchers are 1) categorizing Illinois bluegill populations based on adult size structure using existing creel surveys and standardized sampling, 2) examining life history characteristics in selected impoundments, and 3) determining which factors are controlling size structures in each of these populations. The goal is to develop an adaptive management experiment to assess the ability of several management alternatives in altering bluegill size structure.

Catch-and-release angling in bass
D. Philipp, F. Phelan (Queen's University Biological Station), M. Kubacki (Arizona Game and Fish), C.A. Toline (Utah State University), D.B.F. Philipp (Deutsche Morgan Grenfell)
Because both largemouth and smallmouth bass are highly prized sport fish, many are captured in the spring when males are still on nests providing parental care for their young. Data collected from experimentally captured-and-released bass (e.g., male size, brood developmental stage, egg score, return time, and predation rates) are being used to determine how catch-and-release angling impacts the reproductive success of both species and how those impacts can be minimized.

Yellow perch population assessment
S. Robillard, J.E. Marsden
Adult yellow perch were marked with Floy tags and then recaptured 0, 1.5, 3, and 4.5 NM north and south of the IDNR Lake Bluff index station to identify where spawning concentrations of perch occur. Over 5.5% of the tagged fish were recaptured in their first six months at liberty; during spawning, 55% of the tagged fish were recaptured at the same site they were tagged. The mean age of adult perch has continued to increase due to an ongoing recruitment failure and near absence of younger age groups in the population.

Large- and smallmouth bass reproduction
D. Philipp, J. Claussen, F. Phelan (Queen's University Biological Station), M. Kubacki (Arizona Game and Fish)
For reproduction, male largemouth and smallmouth bass build nests in lake or stream substrates, court and spawn with females, and then remain to protect their brood, providing parental care for up to four to six weeks after fertilization of the eggs. To determine how reproductive success varies among years, researchers have been intensively monitoring the spawning success as well as the duration of nesting and parental care behavior in both species for the past seven years. Four distinct habitats in southern Ontario are being compared to determine the spatial and temporal differences among populations.

Larval fish production in a backwater
P. Raibley, K. Irons, M. O'Hara, D. Blodgett, R. Sparks
Researchers monitored larval fish production in an escapement of Lake Chautauqua, a backwater of the Illinois River managed by the U.S. Fish and Wildlife Service, primarily to produce moist-soil plants for migrating waterfowl. In the lake, researchers collected 36 species of adult fish and 16 taxa of larval fish; estimated standing stocks of larval fish averaged over 200 million. When water was released from the lake in June, researchers sampled the effluent and estimated 17 to 31 million young-of-year fish escaped to the river. It appears some moist-soil management units provide opportunities to produce young-of-year fish to enhance riverine populations.

Vulnerability of largemouth bass to angling
D. Philipp, J. Claussen, D. Burkett (U.S. Fish and Wildlife Service), J. Koppelman (Missouri Department of Conservation), C.A. Toline (Utah State University)
Little is known about the long-term effects of angling harvest on sport fish populations. Research has demonstrated that individual largemouth bass are not equally vulnerable to anglers' efforts. In an experimental population exposed only to catch-and-release fishing, certain bass were never caught, whereas others were captured several times. A selective breeding experiment has further demonstrated that hook-and-line vulnerability is heritable. Researchers are now studying the long-term impacts that heavy angler harvest can have on native largemouth bass populations.

Yellow perch early life history
S. Robillard, J.E. Marsden
Researchers are sampling larval yellow perch to assess the fish's abundance and diel distribution. Young-of-the-year (YOY) yellow perch collections were made with a bottom trawl to assess survival of larvae to the YOY stage. Severely reduced catches of larval and YOY perch indicated that a strong year-class was not produced in 1996, which will mark eight consecutive years of poor recruitment. The effect of alewife predation on yellow perch larvae was assessed. Researchers also developed a method to monitor yearly abundances of perch egg masses and sampled plankton with light traps.

Improving lake resource management
R. Riedel, R. Illyes, D. Philipp, P. Bayley (Oregon State University), D. Austen and S. Sobaski (IDNR Fisheries)
The Fisheries Analysis System is an integrated approach to management and research on Illinois lakes. It incorporates a wide range of information on state-managed lakes, including data from fish population and creel surveys, lake physiochemical properties, and environmental and management histories. This infor-mation is used directly by Illinois Department of Natural Resources managers at district and statewide levels in their management planning. Researchers are using this system to predict fish population trends based on past environmental and management histories so that future fisheries management will be more scientifically based.

Gizzard shad abundance model validated
T. Smith, D. Wahl
Gizzard shad dominate the fish communities and ecology of many midwestern and southern reservoirs in the continental U.S. The ability to manage gizzard shad may have implications for the success of reservoir fisheries across the range of this species. Researchers recently devised a model to predict the abundance of juvenile gizzard shad from characteristics of the spring flood. For the past two years, the model has provided successful a priori predictions of juvenile gizzard shad abundance in Lake Shelbyville. These results demonstrate the potential utility of water level manipulations as a tool for regulating populations and assemblages of fish in systems with managed flows.

Illinois River fish population monitoring
R. Sparks, D. Blodgett, S. Whitney
Since 1957, standardized methods have been used annually to sample fish communities at 27 stations along the length of the Illinois River. This program monitors temporal and spatial trends in fish diversity, abundance, and health. Collected data are used to identify and understand how environmental factors, both natural (such as the drought of 1987-1988 and floods of 1993 and 1995) and anthropogenic (e.g., point and nonpoint pollution), affect fish reproductive success, growth, and survival. This project is funded by the Federal Aid to Sportfish Restoration program of the U.S. Fish and Wildlife Service with cooperation from the Illinois Department of Natural Resources.

Evaluation of esocid stocking program
D.Wahl, L. Einfalt
The stocking program for muskellunge and tiger muskellunge is being evaluated to determine optimal stocking strategies for these fish in Illinois. Mechanisms of survival and growth of various sizes of esocids after impoundment stockings are being compared and used to develop a bioeconomic model. Second, the effect of rearing method in determining susceptibility to largemouth bass predation is being evaluated in impoundment stockings as well as pond and laboratory experiments. Finally, an assessment of different genetic stocks of muskellunge throughout North America and their performance characteristics are being evaluated in physiological experiments.

Indicators for sustainable agriculture
R. Herendeen, D. Onstad, E. Zaborski, A. Winter-Nelson and D. Cavanaugh-Grant (University of Illinois), W. Jackson (The Land Institute, Salina, Kansas)
This project will compare energy, nutrient, and resource budgets at the farm level for conventional and "organic" farms in Illinois and The Land Institute's "Sun Farm" in Kansas. These budgets will be the basis of estimating how long such operations can be sustained. Researchers will use a number of indicators applied to data on inputs and outputs from the farm to compare its sustainability. These will draw from energy analysis, mass-balance analysis, work of The Natural Step Foundation, and some part of the work of Howard Odum, in addition to economics.

Habitat and bluegill growth and prey
S. Callahan, D. Wahl
The littoral zone is an important component of a lake landscape, often associated with a high amount of habitat complexity due to macrophytes. Survey researchers evaluated the effects of habitat complexity on bluegill growth and prey selection using four ponds with macrophytes and four without. Each pond was stocked with 15 kg of small (50 mm) and large (150 mm) bluegill. Growth and prey selection were examined through time. Preliminary analysis indicates slower growth in the complex habitat for small bluegill. With further analysis, researchers hope to better understand the role that the littoral zone environment has on bluegill biology.

Commercial navigation and fish behavior
E. Gittinger, D. Soluk, D. Wahl, J. Dettmers
Barge traffic has the potential to directly increase mortality of fishes. Alternatively, fish may exhibit avoidance behavior and move away from barges in large river systems. This study is being conducted in Pool 26 of the Mississippi River and the lower 35 miles of the Illinois River. Hydroacoustics are being used to observe fish movements before, during, and after barge passage. Purse seining is also being used in the presence and absence of the barges to help verify the hydroacoustical readings and to offer some insight into what fish assemblages are present in the rivers.

Stream habitat assessment using sonar
R. Illyes, S. Kohler, P. Bayley
Assessment of instream physical habitat is often used in conjunction with fish and invertebrate surveys to identify mechanisms responsible for changes in biotic integrity. Such assessments are frequently time consuming and are difficult to perform in many habitats (e.g., deep or highly turbid areas). Survey researchers are attempting to develop a sonar-based device that will allow rapid and effective quantification of major stream-bottom features under a wide range of physical conditions. Data collected by the device will be downloaded to a computer for storage and analysis.

Commercial navigation effects on fishes
J. Dettmers, D. Soluk, D. Wahl
INHS researchers' results reveal that a diverse assemblage of larval, juvenile, and adult fishes use the main channel. The distribution of some large fishes may be influenced by navigation locks and dams. Blue catfish and bigmouth buffalo were present only in more lakelike regions immediately upstream of the lock and dam, whereas lake sturgeon, shovelnose sturgeon, blue catfish, and shorthead redhorse were distributed only well upstream of the dam. In addition to this ongoing sampling, researchers expect to explore indirect effects of commercial navigation on fishes, river food-web interactions, and recruitment patterns of fishes.

Analysis of environmental issues
R. Herendeen
Following a course that he teaches in the Department of Urban and Regional Planning at the University of Illinois, Dr. Herendeen is finishing a book on the use of simple but careful numerical approaches for understanding, and entering the debate about, a wide spectrum of environmental issues. These range from bioaccumulation in fish to planning for electric power plants.

Sedimentation impacts on streams
S. Kohler, D. Soluk
Land-use practices in watersheds can strongly affect the integrity of stream communities. Army training at Fort Bragg, North Carolina, has involved extensive manipulation of the sandhill landscape. This has produced pronounced increases in soil erosion locally and occasionally over extensive areas within some watersheds. Using unimpacted stream reaches as controls, researchers found substantial sediment-induced alterations in habitat, and associated effects on the diversity and population densities of fish and benthic invertebrates. Research results have been used to develop monitoring protocols for watersheds in this region.

Indicators of watershed performance
S. Kohler, D. Schneider, J. Braden, D. White, G. McIsaac, K. McDermaid, J. Vining, R. Cooke, R. Hornbaker
The watershed is recognized increasingly by state and federal agencies as the fundamental spatial unit for natural resource management. Watershed-based management requires a consensus among watershed stakeholders concerning conditions within the watershed, problems to be addressed, and priorities to be assigned to those problems. To aid in the development of such a consensus, INHS researchers are identifying physical, biotic, economic, and social indicators of watershed performance and investigating how they might be used in decision-making.

Resource conflict in river levee districts
D. Schneider
The floodplain of the Illinois River has been contested terrain since the 19th century as the various interests on the river--farmers, commercial hunters and fishers, private hunting clubs, levee districts, and state agencies, including the Illinois Natural History Survey--struggled to control or protect the natural resources of the river. This project investigates the history of this resource conflict. How the struggle played out at the turn of the century continues to affect the current ecology of the floodplain and its potential for restoration.

Presettlement vegetation in floodplains
J. Nelson, R. Sparks
Historical data collected by surveyors of the U.S. General Land Office in large river-floodplains of the upper Mississippi River System are being used to measure changes in the natural system due to modern human activities over the past 180+ years. Results along an 80-mile-long reach of the Mississippi River (Navigation Reaches 25 and 26) indicate that prairie was the dominant plant community on the floodplain in 1816. Dense forests dominated the islands, while savannas and woodlands were also prevalent on the floodplain.

Illinois Streams Information System
D. Schneider, D. Johnston, D. Szafoni
At present, the Illinois Streams Information System (ISIS), developed by the Department of Conservation, is a relational database organized by river and river mile. The narrative text within ISIS represents a valuable compilation of information for managing surface waters, but the text format is not presently compatible with many other state databases housed within a geographic information system (GIS) framework. Work has been completed to allow the information in ISIS to be accessed and referenced by other state databases within a GIS framework. During the conversion, Survey staff managed the ISIS database and responded to requests for information.

Bioassessment of stream integrity
R. Smoger, S. Kohler, D. Austen (Illinois Department of Natural Resources), B. Hite (Illinois Environmental Protection Agency)
The Index of Biotic Integrity (IBI), a measure of water quality based on fish communities, has been used for over 20 years to assess stream quality and classify streams. The IBI will be an important component of biological water quality standards being developed in Illinois. Researchers are refining the IBI for use in Illinois streams by analyzing several aspects of the index, including how components of the IBI vary regionally, identifying reference conditions within regions, the efficacy of IBI components in detecting degraded conditions, and how data from different sampling gears can be combined to estimate fish abundance.

Forests of the Mississippi-Illinois rivers
J. Nelson, R. Sparks
In conjunction with presettlement forest data, results confirm that today's floodplain forests are often overwhelmingly dominated by silver maple. The very successful growth and establishment of silver maple over the past 180+ years is a strong indication that humans have altered one or more of the key processes that once favored a more biologically rich forest community. It is likely that silver maple dominance will continue well into the 21st century unless management plans are enacted to address this problem.

Crayfish predators and plant abundance
T. Smith, D. Wahl
Simple food-chain models assert that predators diminish herbivore density and increase the biomass of plants. Food-chain models for shallow lentic systems predict large fish predators will reduce grazing by crayfish and allow rooted macrophytes to proliferate. Researchers have shown that the effect of largemouth bass on crayfish populations in ponds varies considerably among crayfish species. Thus, the composition of crayfish assemblages changes in the presence of fish predators. Predator-resistant crayfish species may buffer direct and indirect effects of predators. Additional research will determine if changes in crayfish assemblages also buffer the effects of predators on macrophytes and algae.

Long-term Resource Monitoring Program
R. Sparks, D. Blodgett, T. Mihuc
Two Survey field stations participate in the Long-term Resource Monitoring Program for the upper Mississippi River System. The LTRMP is a cooperative effort of the U.S. Army Corps of Engineers, the U.S. Geological Survey's Biological Resources Division, and resource agencies of the five upper Mississippi River states including Illinois. Using standardized methods and equipment, station staffs monitor aquatic and terrestrial vegetation, water quality, selected macroin-vertebrates, and fish. One station at Havana monitors La Grange Reach of the Illinois River, and the second station at Alton monitors Reach 26 of the Mississippi River and lower Alton Reach on the Illinois.

Common carp research
J. Parkos, V. Santucci, Jr., D. Wahl
Even though it is suspected that common carp can maintain shallow lakes as highly turbid systems dominated by algae, very little work has been done to evaluate the effects that these fish have on aquatic systems. At the same time, previous efforts to remove these fish have been mostly unsuccessful. This project, in collaboration with the Max McGraw Wildlife Foundation, will quantify the effects that common carp have in aquatic systems and test the effectiveness of a plastic mesh in the mitigation of the environmental damage caused by these fish.

Zebra mussel predation by common carp
F. Cronin, J. Tucker, D. Soergel, T. Mihuc
Examinations of gut contents from common carp collected in the Mississippi River have shown evidence of carp predation on zebra mussels. Researchers found between 1 and 407 zebra mussel beaks in 83.9% of the fish examined. Scientists are currently investigating size-selective predation by carp on zebra mussels and potential impacts of common carp, which are numerous in the Illinois and Mississippi rivers, on zebra mussel demographics.

Determining zebra mussel metabolic rates
S. Madon, D. Schneider, J. Stoeckel, R. Sparks
Measurements of metabolic rate are vital to studies on energetics and functional responses of zebra mussels to environmental variables. However, laboratory estimates of metabolic rate often fail to reflect metabolic costs in natural systems. The electron transport system (ETS) enzyme assay provides a method for measuring metabolic rates in zebra mussels in rivers. Zebra mussel respiration has been calibrated with ETS activity in the laboratory. We are now employing this technique to determine metabolic rates and oxygen demand of zebra mussel populations in the Illinois River.

Metapopulation modeling of zebra mussels
D. Schneider, S. Aggarwal, J. Stoeckel, R. Sparks, B. Hannon
Populations of zebra mussels in the Illinois River may be maintained in the face of suboptimal conditions in the river by continued immigration from Lake Michigan. Researchers are developing a metapopulation model of the zebra mussel in the Illinois River, based on immigration of larvae from Lake Michigan, to predict the variability of mussel populations in the river and search for critical opportunities for control.

Exotic zooplankton in Illinois
C. Kolar, J. Boase, D. Wahl
Exotic species lack natural predators and other population control mechanisms found in their native ranges. For these reasons, exotic species can have profound effects on native populations. Recently, Survey scientists discovered Daphnia lumholtzi, a species of zooplankton found in Australia, Asia, and Africa, to be the dominant daphnid in Lake Springfield by late summer. D. lumholtzi has also been found in an additional 12 reservoirs within the state. Researchers are conducting experiments to examine the competitive ability and vulnerability of D. lumholtzi to fish predation. Results of these experiments will aid in predicting the potential ecological impact of this exotic daphnid on aquatic communities.

Zebra mussel seasonal dynamics
T. Mihuc
Current research emphasizes habitat requirements and seasonal patterns in zebra mussel colonization in neotropical and temperate large floodplain rivers in North America. Temperature and dissolved oxygen tolerances may inhibit the establishment of permanent populations laterally into floodplain habitat in many rivers, particularly at the southern periphery of the current invasion where tolerances are often exceeded during summer months. A multiregion comprehensive project of zebra mussel source-sink linkages and movement vectors is in the planning stages.

Zebra mussels in the Illinois River
K. Stevenson, D. Blodgett
Zebra mussel colonization, survival, and growth rates are being assessed using artificial substrate samplers at seven sites along a 200-mile reach of the Illinois River. Researchers deployed seven sets of triplicate samplers at each site in spring and retrieved one set from each site monthly. During 1996, highest densities occurred upriver, but growth rates were greater in the middle river. This research is coordinated with similar efforts of the U.S. Army Corps of Engineers Waterways Experiment Station in other North American rivers. Data collected will aid in understanding factors that control zebra mussel distributions and abundance.

Zebra mussel effects on native mussels
D. Schneider, C. Ellis, K. Cummings, R. Sparks
INHS researchers are using data on boat traffic in Illinois lakes and rivers to develop a probabilistic model of zebra mussel spread in Illinois. This will be coupled in a geographic information system with collections records for native mussels to predict communities of native mussels at greatest risk from the zebra mussel.

Round gobies in Lake Michigan
D. Soluk, J.E. Marsden, K. Wolfe
Round gobies invaded Lake St. Clair from eastern Europe in 1990, and had spread to all of the Great Lakes by 1995. The population of gobies in southern Lake Michigan exceeds 40 /m² in places. Researchers are examining the spread of gobies within Lake Michigan, their impact on native benthic fishes, such as sculpins, and their appearance in the diet of sport fish species. The territorial and seasonal movements of gobies are also being tracked using mark-and-recapture techniques.

Daphnia lumholtzi in the Illinois River
J. Stoeckel, K. Stevenson, K. Blodgett, R. Sparks
Daphnia lumholtzi, an exotic zooplankter, was first detected along the lower 195 miles of the Illinois River in 1995 and is thought to have invaded from the south. In 1996 researchers collected specimens 104 miles farther upriver and only 30 miles from Lake Michigan. Densities and fecundity were similar to those reported in lakes and reservoirs, suggesting D. lumholtzi adapts to lotic as well as lentic systems. Through upriver transport, possibly by commercial and recreational watercraft, introduction into Lake Michigan appears imminent; whether D. lumholtzi thrives in the colder waters remains to be seen.

Zebra mussel growth in the Illinois River
D. Schneider, R. Sparks, J. Stoeckel, S. Madon
Researchers are measuring growth of individually marked zebra mussels in various habitats in the Illinois River floodplain ecosystem to evaluate the role of temperature, sediment, and body size on zebra mussel growth. Measured growth rates will be used to calibrate an energetic model. Also being evaluated are the effects of natural and artificial suspended sediment on the energetics budget of the zebra mussel. These data will be used to develop a predictive model of zebra mussel growth in turbid river ecosystems.

Potential invasion of round goby in Illinois
D. Soluk, W. Resetarits
Preliminary experimental studies of growth and thermal tolerance indicate a potential for round gobies to occupy both coldwater and warmwater stream systems throughout most of North America. Ongoing studies suggest the potential impact of round gobies on streams is high, especially for populations of other smaller benthic fishes (e.g., darters) that may be displaced or directly consumed by gobies. Research focuses on quantifying the current range of gobies in the canals that connect the upper Illinois River with Lake Michigan, and providing an assessment of the potential final range and impact of gobies on habitats outside of the Great Lakes.

Zebra mussel impacts on native mussels
J. Stoeckel, S. Whitney, T. Snider, D. Blodgett
While high densities of zebra mussels have been linked to mortality in native mussels, the mechanisms causing mortality are poorly understood. Because native mussels store energy as glycogen, Survey researchers are investigating the effects of zebra mussel infestation on glycogen levels and mortality in three species of native mussels. In the laboratory, native mussels were exposed to dense infestations of zebra mussels, and glycogen levels and mortality were monitored before and after the experiments. Analysis of collected data is under way and may help researchers better understand the relationships between zebra mussel infestations and mortality in native mussels.

Ecology of Hine's emerald dragonfly
D. Soluk
Hine's emerald dragonfly is a federally listed endangered species restricted to a small portion of the Des Plaines River Valley in Illinois and in Door County, Wisconsin. The exact habitat requirements of larvae and adults are still unclear. Such knowledge, and additional information on life history patterns are crucial for developing plans to protect this species and predict the effects of any particular type of disturbance. Research focuses on life history and patterns of habitat use by both adults and larvae of this species with a particular emphasis on quantitative assessments of the importance of both biotic and abiotic factors in limiting the distribution of Hine's emerald dragonfly.