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CENTER FOR AQUATIC ECOLOGY

Description --- Public Service --- Special Recognition --- Project Summaries

The Center for Aquatic Ecology maintains eight field stations: the Aquatic Research Field Laboratory in Champaign, the Sam Parr Biological Station at Kinmundy, the Ridge Lake Station near Charleston, the Lake Michigan Biological Station at Zion, the Kaskaskia Biological Station on Lake Shelbyville, the River Research Laboratory at the Stephen A. Forbes Biological Station in Havana, the Mississippi River-Reach 26 Research Station at Alton, and the Illinois River-LaGrange Reach Research Station at Havana. This important system of field stations allows Center scientists to conduct needed field research on site.

The primary activity of Center scientists is to conduct research. Their findings are disseminated in a number of ways. Presentation to peers at scientific conferences represents the most timely avenue. This past year, Center scientists delivered 9 departmental seminars at a variety of universities throughout the country and made over 46 scientific presentations at international, national, regional, and state conferences. In addition, two Center scientists organized major symposia. Dr. Richard E. Sparks organized the Ecological Society of America's Special Symposium on "Disturbance, Succession, and Ecosystem Processes in Rivers and Streams." Dr. William J. Resetarits organized a symposium entitled, "The State of Experimental Ecology: Questions, Levels, and Approaches," held at the annual meeting of the American Society of Zoologists. The results of this latter symposium were highlighted in several issues of Science.

Center scientists also recognize the importance of providing information directly to the citizens of Illinois; presentations were made to many local and statewide nature clubs, fishing groups, governmental agencies, and other organizations. In addition, Center scientists were major contributors to a number of magazine and newspaper articles as well as to two television specials (NOVA: "The Great Flood of 1993" and The Nature of Things: "Floods and Floodplains"). Center scientists provide timely findings to the governmental agencies that are funding specific research projects; over 20 final reports were submitted this year alone. Publications in peer-reviewed journals constitute the final and most definitive avenue. Center scientists published over 30 papers on a variety of topics in high-quality widely disseminated journals.

The Center for Aquatic Ecology is very active in conducting research. This high level of activity is made possible by research grants and contracts 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 1995. Support for these projects, totaling over $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 five post-doctoral associates, 34 graduate students (9 Ph.D. and 25 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 non-governmental and professional organizations. Once again, Center scientists actively participated at all levels. The following are highlights of the past year's activities: 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 Non-indigenous Aquatic Nuisance Species. Dr. Sparks served at several levels as an advisor to The Nature Conservancy. Drs. Daniel Schneider and Sparks served on the Lieutenant Governor's Illinois River Task Force. Dr. David P. Philipp served on the Colorado River Endangered Fishes Recovery Program's Genetics Panel.

The Center for Aquatic Ecology is especially proud of the contribution that Dr. Sparks and his colleagues at the Center's three large river field stations are making to develop a better understanding of both the impacts of and reasons for the floods of 1993 and 1995. Beyond providing a wealth of sound scientific data through their major research efforts over the last 20-plus years on the Illinois and Mississippi rivers, this group is also helping to shape policy and future management directions at the state and federal levels. For example, Dr. Sparks serves on the following prestigious national committees: The Advisory and Review Committee for Water Resources Research within the U.S. Geological Survey (USGS); the Water Science and Technology Board of the National Academy of Science's National Research Council; Illinois River Basin Study Groups of the USGS National Water Quality Assessment Program; and The President's Council on Sustainable Development. In addition, Dr. Sparks serves on the planning committee that advises the Lieutenant Governor's Illinois River Strategy Team. It is through efforts such as these that the Center for Aquatic Ecology is helping to better understand, manage, and conserve our aquatic resources.

Conservation Biology

Lake trout reproduction in Lake Michigan
M Chotkowski, J.E. Marsden
Stocked lake trout have failed to reproduce successfully in Lake Michigan and the other Great Lakes. The construction of breakwalls and intake structures may provide habitat that is used by stocked lake trout for spawning. Survey researchers are comparing egg deposition, fry survival, and the effect of predation by native and introduced fish species (sculpins, gobies, carps, and alewives) on natural versus man-made structures. Preliminary data indicate that man-made structures are more heavily used for spawning than natural areas; however, these areas tend to be shallow and are therefore inhabited by a greater variety of potential egg predators than natural, offshore reefs.

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 F, 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.

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 makoup of that population is disrupted, a change that often has negative effects. To assess these potential negative impacts, researchers conducted a series of experiments to compare survival, growth, and reproductive success of genetically defined stocks of largemouth bass in different geographic habitats. In all experiments, survival, growth, and reproductive success of the local stocks were superior to those of the introduced stocks. In addition, extensive introgression among stocks occurred within a very few generations and the performance of introgressed individuals was poorer than in the pure local stock.

Genetic analysis of sportfish populations
R. Fields, M. Desjardins, T. Kassler, J. Ludden, M. Hudson, V. Tranquili, D. Philipp, M. Jennings and M. Staggs (Wisconsin Department of Natural Resources), P. Wingate (Minnesota Department of Natural Resources), C. Toline (Utah State University)
The stock concept states that species of fish are composed of genetically distinct populations that are uniquely adapted to their environments. To identify individual stocks of key sportfishes, researchers are analyzing populations of 12 species of fish from distinct watersheds in the upper Midwest. Three molecular genetic techniques - protein electrophoresis, RFLP analysis of mitochondrial DNA, and RAPD DNA analysis - are being used to assess the genetic variation present within and among populations of each species.

Illinois chorus frog studies at I-255 site
J. Tucker, D. Philipp
The fossorial Illinois chorus frog (Pseudacris streckeri illinoensis), a threatened taxon in Illinois, is distributed mainly along the Illinois River and scattered along the Mississippi River floodplain from Madison to Alexander counties. A proposed highway interchange near Poag (Madison County) will impact a site where this frog has been heard calling. Research objectives are to determine the distribution of the frog's choruses, the approximate number of breeding individuals, and the suitability of three alternate wetland mitigation sites as potential habitat. A strategy to improve habitat for the frog will be developed.

Amphibian species diversity
W. Resetarits, J. Fauth (College of Charleston)
An important goal of ecology is to identify and understand the processes that generate and maintain species diversity. Understanding these processes is also critical to the preservation of biodiversity. This study focuses 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.

Modeling of zebra mussel populations
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 by continued immigration from Lake Michigan. Survey 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 to search for opportunities for control.

Ecology of Hine's emerald dragonfly
D. Soluk
Hine's emerald dragonfly (Sommatochlora hineana) is a federally listed endangered species whose only known populations occur in a short stretch of the Des Plaines River valley and in Door County, Wisconsin. In both these areas this species is potentially threatened by the development of industry, tourism, and roadways. The species is associated with seep areas that receive groundwater flows from dolomitic limestone formations. The exact habitat requirements of larvae and adults are still unclear. Acquiring such knowledge, and additional information on the species' life history panerns are crucial for developing plans to protect it and predict how biotic and abiotic disturbances limit the distribution of Hine's emerald dragonfly.

Reproduction of the red-eared slider
J. Tucker
The red-eared slider (Trachemys scripta elegans) is an abundant inhabitant of lotic systems and particularly characteristic of river backwater habitats. This research investigates the reproductive ecology of this turtle at three nesting areas. The primary focus of the study is to determine patterns in reproductive effort at each locality. With a multi-year data set, the effects of the 1993 and 1995 floods on red-ear reproduction should become apparent. One of the populations occupies Swan Lake, the target of a habitat rehabilitation and enhancement project. The effect of this project is also under study. Also, basic evolutionary questions about egg size and number are being studied.

Mussels of the Illinois River
S.Whitney, D. Osland, D. Blodgett, R. Sparks
Mussels in the Illinois River are showing signs of recovery after decades of decline. Upstream, near Chicago, where no live mussels had been reported since the early 1900s, Survey researchers found healthy individuals of 12 species. A total of 23 species are living in the river, including 5 species once listed as extirpated; the number of species and individuals increases downriver. Most mussel beds in the lower river have several abundant species rather than just one or two dominant species as in the past. The mussels are reproducing and grow faster than mussels from a sanctuary in the Upper Mississippi River that serves as a reference site.

Population/Community/Systems Ecology

Trophic interactions in ecosystems
R. Herendeen
Trophic cascade and bottom-up:top-down hypotheses are used in this study to describe and predict how perturbing one organism affects the others in an ecosystem. Initial evidence from aquatic systems has recently been supplemented with terrestrial examples. From this research a quantitative general theory has been 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 more general approach is applicable to food webs as well as just to chains, and to a wide range of interactions among organisms.

Mainstream channel fauna of rivers
D. Soluk, R. Sparks, S. Kohler
The mainstream channels of rivers, dominated by loosely consolidated sandy sediments, are generally considered to be a hostile habitat for benthic fauna. Studies, however, have revealed that there are many organisms living in and on these sediments. Little is known about these communities and their importance to river ecosystems, and still less is known about the effects on them from human activities and channel modifications. Research in the upper Mississippi and Illinois rivers is focusing on how mainstream channel fauna are affected by silt-loading from agriculture and modification of the channel to facilitate navigation.

Energy Analysis and EMERGY analysis
R. Herendeen, M. Brown (University of Florida)
Researchers have completed a detailed comparison of two environmental accounting schemes (energy analysis and EMERGY analysis) for internal consistency, agreement with existing science, and usefulness; it is now in press in Ecological Economics. While energy analysis' accounting scheme is relatively rigorous and well-publicized, it does not quantify the environment's role in absorbing, processing, and neutralizing pollution and environmental impacts. EMERGY analysis attempts this more comprehensive accounting, but its accounting scheme has been unavailable in open literature until now.

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 preinfection levels.

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 on the organization of stream communities have received little study. Recent 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 to date 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.

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 other areas. An alternative explanation is that organisms may simply travel upstream after drifting downstream for some time. Using innovative technology, researchers are measuring upstream movement and colonization under natural conditions.

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 caddiefly 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.

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

Spawning dynamics of bluegill
J. Claussen, D. Philipp
Bluegills have highly social reproductive behaviors in which some males build nests in colonies, court and spawn with females, and provide all parental care for the young in the nest. This study monitors the annual variation in the number of males that build nests, spawn, and successfully raise a brood off the nest in a study area of Lake Opinicon, Ontario. Yearly comparisons determine how environmental changes, such as temperature, affect variation in the number of breeding males and females, as well as how changes in the overall breeding population affect clutch size. These data provide information for modeling bluegill population dynamics in the Midwest and will aid in creating successful management programs.

Interspecific hybridization and cuckoldry
B. Konkle, J. Claussen, D. Philipp
Bluegill and pumpkinseed are two species of sunfish that readily hybridize. Researchers are studying these hybridization events in Lake Opinicon, Ontario, to determine how and why they occur. These two species also exhibit alternative reproductive strategies, including the use of cuckoldry. Using behavioral observation and underwater videos, researchers discovered that spawning pairs of pumpkinseed were being parasitized by cuckolder male bluegill. Molecular techniques confirmed that, in fact, all natural interspecific hybrids were the result of matings of pumpkinseed females and bluegill males. Current research attempts to determine the evolutionary significance of these events.

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.

Lake trout spawning on deep reefs
J.E. Marsden, J. Janssen
Efforts to restore selfsustaining populations of lake trout in Lake Michigan have focused on deep reefs, where historic stocks were presumed to have spawned. However, to date no evidence of spawning by stocked lake trout has been collected from waters deeper than 15 m. We tested a remotely operated underwater vehicle equipped with a suction sampler for collection of lake trout eggs at depths inaccessible to divers. We collected five lake trout eggs and three sculpins which had eaten eggs at 30 m on Julian's Reef. This work demonstrates a new technique for studying lake trout reproduction and collecting egg predators on deep reefs.

Brook trout-spring salamander interactions
W. Resetarits
The 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 on interactions between spring salamanders and brook trout to determine the specific factors that contribute to the maintenance and dynamics of spring salamander populations in streams containing brook trout, and the use of this as a model system for studying complex mechanisms of species coexistence under asymmetric competition.

Twinning in the red-eared slider
J. Tucker
In a previous study, it was found found that 80% of eggs containing twins produced a large living twin and a small dead twin. This suggested that some sort of brood reduction was at work that effectively maximized fitness by producing one hatchling of near-normal size as compared to two very small hatchlings. A follow-up study will track the developmental histories of twin embryos to determine why one twin dies at an early embryonic stage. A preliminary attempt to artificially augment yolk resources of eggs containing twins will be made with a subset of these eggs. The purpose of this experiment is to determine whether artificial manipulation can alter the expected fate of the twins.

Hatchling size in the red-eared slider
J. Tucker
This study investigates whether large hatchlings fair better (i.e., is big better?) than smaller ones during the post-emergence migration from the nest to water. A large number of hatchlings will be released at a natural nesting area in four replicates at two different distances. The effects of family and hatchling size will be tested.

Freeze tolerance in the Illinois chorus frog
J. Tucker, G. Packard (Colorado State University)
This experimental work will determine whether or not the Illinois chorus frog is freeze tolerant, an aspect of the natural history of this fossorial frog that is unknown. The findings may help explain the relictual distribution and restricted hjabitat requirements of this species. Furthermore, the study will provide information for management decisions concerning vegetation coverage for the Madison County chorus frog mitigation effort.

Individual-based model for walleye
T. Galarowicz, D. Wahl, R. Herendeen
Fish growth and population dynamics are influenced by size-dependent mechanisms and physical factors. Individual-based models, which follow individuals of a species rather than an "average" individual, provide additional insight into these relationships. A model written for walleye and perch in Lake Oneida, New York, will be modified using laboratory and field data collected from Illinois reservoirs. Information from model simulations will then be used to develop and improve stocking strategies for walleye.

Factors that determine larval fish growth
R. Claramunt, D. Wahl
Survey researhers are evaluating the role of several environmental factors in determining the growth of several larval fish species. Sampling was conducted in inshore and offshore habitats using push nets in 21 Illinois reservoirs. Larval sunfish, crappie, gizzard shad, and minnows were collected from May through July. Lakes were classified based on morphometric and limnological variables and compared to larval fish growth rates. Latitude, lake temperature, and characteristics of zooplankton populations (species and size composition) appear to be most highly correlated with growth. Our results will help to make predictions of fish reproductive success and recruitment across systems.

Predator effects on littoral communities
T. Smith, D. Wahl
The trophic cascade hypothesis (TCH) predicts that in aquatic food chains, predators such as largemouth bass should reduce numbers of plankton-eating fish, increase zooplankton grazers, and decrease production of algae. Some experiments seem to support TCH, but almost none of these have measured the simultaneous effect of predators on littoral food chains containing crayfish and submersed aquatic plants. INHS researchers have initiated experiments in ponds and mesocoms to measure responses of prey in littoral and open-water food chains, and to quantify the importance of each pathway as a regulator of productivity in aquatic systems.

Fisheries Management and Ecology

Modeling of walleye and gizzard shad
T. Galarowicz (University of Illinois), R. Herendeen, D. Wahl
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. Survey 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 Kaskaskia Biological Station.

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

Sport fishing in Lake Michigan
W. Brofka, J.E. Marsden
Sport fishing in the Illinois waters of Lake Michigan was surveyed from March through November using a creel survey. Data collected from anglers included fishing activity, fish harvest, and monetary expenditures. Samples of creeled fish were measured and weighed. Estimated total fishing effort for pedestrians and boaters was 796,000 angler-hours. Estimated total harvest included 566,000 yellow perch, 4,700 brown trout, 6,900 rainbow trout, 5,000 lake trout, 28,000 coho salmon, and 6,000 chinook salmon. Catches for all species increased compared to 1994 except for lake trout and coho salmon. Estimated expenditures related to fishing were $8.6 million. An additional March survey was conducted at eight sites in 1995.

Yellow perch population assessment
S. Robillard, J.E. Marsden
Adult yellow perch were sampled using Illinois Department of Natural Resources (IDNR) graded-mesh gill nets and INHS fyke nets to compare assessment gears. More fish were captured in fyke nets, and gill nets targeted larger fish; however, age-compositions were similar. Adult yellow perch were sampled at various distances north and south of the IDNR Lake Bluff index station to determine whether spawning concentrations of perch occur. Aggregations of perch were nearly equally distributed between the sample sites. The mean age of adult perch has continued to increase due to an ongoing recruitment failure and near-absence of younger age-groups.

Yellow perch early life history
S. Robillard, J.E. Marsden
Yellow perch are currently declining in Lake Michigan due to poor recruitment in the first year of life. Survey researchers are sampling larval yellow perch to assess their abundance and diel distribution. They are also sampling zooplankton to determine whether the available food supply for larval fish has dramatically changed over the past decade. 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 1995, which will mark seven consecutive years of poor recruitment.

Bass reproductive success
D. Philipp, F. Phelan and H. Ferguson (Queen's University Biological Station), M. Kubacki (Arizona Game and Fish)
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 six years. Four distinct habitats in southern Ontario are being compared as well to determine the spatial and temporal differences among populations.

Catch-and-release angling in bass
D. Philipp, F. Phelan (Queen's University Biological Station), M Kubacki (Arizona Game and Fish;), C. Toline (Utah State University), D.B.F. Philipp (Merrill Lynch)
Both largemouth and smallmouth bass are highly prized sportfish, and many are captured in the spring when males are sitting on nests providing parental care for their young. Little is known about how catch-and-release angling affects the reproductive success of nesting bass. Data are being collected from capturedand-released bass: male size, brood developmental stage, egg score, return time, and predation rates. This information will be used to determine how catch-and-release angling impacts the reproductive success of both species and how those impacts can be minimized.

Reproductive strategies in bluegill
D. Philipp, J. Claussen, M. Gross (University of Toronto), M Jennings (Wisconsin DNR), D. Pereira (Minnesota DNR)
Male bluegill exhibit two mutually exclusive alternative reproductive strategies. In the first strategy (parental care), males delay maturation, build nests in colonies, court and spawn with females, and show parental care. In the second strategy (cuckoldry), males mature at a much younger age and smaller size and "steal" fertilizations from spawning parental males by sneaking into their nests or by mimicking females. In addition, age at maturation of parental males appears to be highly phenotypically plastic. How these life history characteristics influence population size structure is being evaluated in an effort to better manage bluegill.

Vulnerability of largemouth bass to angling
D. Philipp, J. Claussen D. Burkett (U.S. Fish and Wildife Service), J. Koppelman (Missouri Department of Conservation), C. Toline (Utah State University) Little is known about the long-term effects of angling harvest on sportfish 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.

Creel surveys on Illinois impoundments
P. Perea, B. Carroll, J. Machung, D. Philipp, P. Bayley (Oregon State University), D. Austen and S. Sobaski (Illinois Department of Natural Resources Fisheries)
Since 1987, INHS scientists have conducted angler surveys on a total 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. The data collected are 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 as well as the impact of sport fishing intensity on the resource.

Improving lake resource management
R. Riedel, R. Illyes, D. Philipp, P. Bayley (Oregon State University), D. Austen and S. Sobaski (Illinois Department of Natural Resources Fisheries)
The Fisheries Analysis System is an integrated approach to management and research on Illinois lakes. It uses a wide range of information on state-managed lakes, including data from fish population and creel surveys, lake physio-chemical properties, and environmental and management histories. Data from more than 300 lakes have been accumulated to date. This information is used directly by 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.

Illinois River fish population monitoring
R. Sparks, T. Lerczak, D. Blodgett
Yearly monitoring of fish populations at 26 stations was completed in September, yielding 48 species plus three hybrids, representing 14 families. The non-native Asian grass carp was collected for the first time during this project. Fish communities were similar to those found in recent years. In terms of both weight and numbers collected, gizzard shad and common carp were abundant in all reaches. Upper river reaches nearest to Chicago continued to support the largest populations of minnows, providing a good forage base for sport fishes such as smallmouth and largemouth bass.

Flood pulse effects on fish recruitment
K Irons, P. Raibley, T. O'Hara, R. Sparks, D. Blodgett
Survey researchers compared yearclass strength and growth of four fish species in the La Grange Reach of the Illinois River from years with relatively small (duration and height) spring floods (1991, 1992, 1994) to those with greater floods (1993, 1995). More small (age-O) largemouth bass, bluegill, black crappie, and white bass were collected during the flood years. Most ages of largemouth bass and bluegill grew faster during years with higher, more protracted floods. No significant differences in growth were observed for black crappie or white bass. Most riverine fish benefit from protracted spring floods that provide additional habitat for spawning and nursery.

Effects of sediment on zebra mussel growth
D. Schneider, S. Madon, J. Stoeckel, R. Sparks
Researchers are evaluating the effects of suspended sediment on the energetics budget of the zebra mussel. These data are being incorporated in an energetics model to predict zebra mussel growth under various sediment regimes in turbid river ecosystems. Growth of individually-marked zebra mussels was measured in "1995" in various habitats in the Illinois River floodplain. Growth data will be compared against energetics model predictions. Data thus far indicate that zebra mussels are poorly adapted to highly turbid environments.

Effects of gizzard shad on aquatic systems
D. Clapp, D. Wahl
As part of a multi-year study evaluating factors influencing survival and growth of walleye, Survey researchers evaluated prey and predator populations in Ridge Lake. In 1989, gizzard shad were accidentally introduced, and they became an important prey resource. By looking at data from before and after the introduction of gizzard shad, researchers can evaluate the impact of the introduction on various trophic levels in the lake.

Evaluation of walleye stocking program
D. Clapp, D. Wahl
Little is known about the relative importance of various factors influencing walleye stocking success. Two basic strategies have been developed: to stock large numbers of relatively inexpensive fry in the hopes that they will survive and contribute to the fishery, or secondly, to stock smaller numbers of more expensive intermediate to advanced fingerlings, assuming that larger fish will lead to strong year classes. Both strategies have had variable success and the reasons are not known. The current study is investigating the influence of various biotic and abiotic factors on walleye stocking success.

Evaluation of esocid stocking strategies
D. Wahl, D. Clapp
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.

Walleye foraging, growth, and survival
C. Kolar, D. Wahl
Although juvenile walleye are stocked extensively throughout most of the United States, not much is known about the mechanisms controlling their growth and survival. As a result, the success of walleye stockings has varied considerably. Survey scientists 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.

Chubsuckers as forage in small lakes
R. Eberts, V. Santucci, Jr., D. Wahl
Young bluegills are the principal forage fish in most small impoundments. However, in this 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.

Effects of starvation in young walleye
J. Jonas, D. Wahl
The direct and indirect effects of starvation in young walleye are being investigated in both behavioral and laboratory investigations. Walleye are being studied after varying periods of starvation at four critical periods in the first year of life. Direct effects of starvation are being observed as changes in total body energy, condition, and mortality rates of fish. The indirect effects of starvation may be seen as a decrease in foraging efficiency or an increase in a fish's vulnerability to predation. From this research we will create predictive models for determining the relative health of young walleye.

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 United States. 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 that includes the 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. INHS researchers will use a bioenergetics model to study these different components affecting culture success.

Factors affecting growth of fish
S. Callahan, D. Wahl, C. Pierce
Survey researchers evaluated the importance of abiotic and biotic factors in determining the growth of three fishes common to Illinois waters: bluegill, largemouth bass, and channel catfish. Fourteen lakes selected for study were characterized based on their morphology and limnology. Small bluegill and channel catfish growth was related to the amount of littoral zone found within the lakes. Large bluegill growth was related to the latitude of the lake. There were no significant relationships with any size of largemouth bass. The results of this study have provided a number of testable hypotheses to help guide future research and management.

Effects of electrofishing on bluegill
S. Callahan, D. Wahl
Survey scientists evaluated the indirect effects of electroshock on bluegill. Feeding rates of large and small 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 imediately after shock than unshocked fish. Within 10 minutes, however, the shocked bluegill were no more susceptible than their unshocked counterparts. The results suggest there are no long-term indirect effects of electroshock on bluegill feeding and susceptibility to predation.

Habitat/Land Use

Indicators for sustainable agriculture
R. Herendeen, M. Bender (The Land Institute, Salina, Kansas)
The Land Institute's "Sun Farm" project strives to be much more sustainable than conventional agriculture. 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 part of the work of Howard Odum, in addition to economics.

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 sandhills landscape. This has produced pronounced increases in soil erosion locally and, in some cases, over extensive areas within some watersheds. Survey researchers are investigating how and to what extent physical habitat characteristics of Fort Bragg streams and their fish and benthic invertebrate communities are affected by increased sedimentation, using unimpacted streams as controls. Research results should lead to more effective means of monitoring stream integrity in this region and in Illinois.

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 timeconsuming 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.

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

Natural capital of Illinois
R. Herendeen, J. Mukherjee (University of Illinois)
In the Illinois Critical Trends Assessment Project, researchers evaluated, in physical terms, the net accumulation of many nonrenewable and renewable resources in Illinois, including fossil fuels, timber, and soil. Scientists evaluated these changes in economic terms as a correction to the gross state product (GSP). GSP is a measure of income, and it was corrected for the loss or gain in wealth that made that income possible, thus presenting a picture of how well off Illinois is. For example, estimates of coal reserves increased in the period 19661981, leading to a positive correction to GSP. Today, coal is being slowly depleted, leading to a negative correction.

Illinois Streams Information System
D. Schneider, D. Johnston, D. Szafoni
At present, the Illinois Streams Information System (ISIS), developed by the former 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.

Presettlement floodplains
J. Nelson, R. Sparks
Data collected by U.S. General Land Office surveyors in the early 1800s allows ecologists to measure changes in the natural system due to human activities since that time. Preliminary 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.

Test model for gizzard shad recruitment
T. Smith, D. Wahl
Annual variation in the size and abundance of gizzard shad affects the growth of predators and the late-summer abundance of zooplankton flood resources for larval and juvenile fish. Using hydrographs from the Corps of Engineers and seven years of data from electrofishing conducted at the Kaskaskia Biological Station in Lake Shelbyville, researchers devised an empirical model predicting the abundance and final size of juvenile gizzard shad. Parameters included the height and timing of spring water-level rises. Characteristics of the 1995 juvenile gizzard shad cohort in Lake Shelbyville conformed to predictions of the model. Testing of the flood model in Lake Shelbyville will continue.

Effects of inundation on bottomland timber
J. Nelson, R. Sparks
In 1937, Survey researcher Lee Yeager documented the effects of river impoundment on standing timber. Yeager's study area was at the confluence of the Illinois and Mississippi rivers and is known locally as Calhoun Point. Yeager's forest data will be compared to forest data researchers collected in 1996 using identical methods. The data comparison will provide some measure of long-term effects of river impoundment on forest succession.

1993 flood effects on forest communities
J. Nelson, R. Cosgriff, R. Sparks
In 1995, Survey researchers established permanent forest sampling plots along Mississippi River Reach 26 to evaluate short-term impacts as well as long-term responses of various forest communities to the 1993 flood. Tree mortality was severe and reached 100% in some places, but the forests are regrowing. Regeneration of silver maple, which was a dominant tree species prior to 1993, was estimated at 205,770 seedlings per hectare on sites classified as maple. However, on sites classified as oak, silver maple seedling counts were much lower at 8,706 seedlings per hectare.

Round gobies in Lake Michigan
J. Marsden, K. Wolfe, M. Chothowski, C. Dolan
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 per 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. INHS scientists are also tracking the territorial and seasonal movements of gobies using mark-and-recapture techniques.

Illinois RiverWatch Network
D. Stoeckel, R. Sparks
The Illinois RiverWatch Network is a partnership of Illinois citizens interested in the quality of the state's rivers and streams. Two hundred volunteers monitored 108 stream sites on 97 streams throughout the state during the first annual citizen-scientist stream monitoring assessment (May 1 - June 30, 1995). Forty-seven of the monitored streams were not regularly monitored by the IEPA. The first year showed, conclusively, that volunteers can be trained to collect quality scientific data. Citizen-scientist stream monitoring data are available through IDNR's ECOFORUM bulletin board system (1-800-528-5486).

Navigation effects on river fishes
J. Dettmers, D. Soluk, D. Wahl
Towboat and barge traffic has the potential to directly increase the mortality of fishes in the main channel of the Mississippi River. To describe this potential, researchers will monitor the abundance and distribution of fishes in Pool 26 of the Mississippi River as well as estimate the proportion of fishes killed by towboats. In addition, we expect to explore indirect effects of commercial navigation on fishes, river food-web interactions, and recruitment patterns of fishes.

Invasive Species

Zebra mussel impact on native gastropods
T. Keniry, J.E. Marsden, D. Padilla, D. Schneider
Zebra mussels are widely known to harm native unionids by colonizing their shells; they are also likely to adversely affect other hardshelled species, such as snails and crayfish. In laboratory experiments researchers are examining the effects of zebra mussel fouling on snail fecundity (egg production), feeding rates, and growth. Field data indicate that fouling varies among species and habitat types of snails. While few snails had zebra mussels attached at the time of collection, examination of the shells for signs of prior attachment indicated that fouling may be a significant problem.

Risk analysis of zebra mussels
D. Schneider, C. Ellis, K. Cummings, R. Sparks
Survey scientists are using data on boat traffic in Illinois lakes and rivers to develop a probabilistic model of zebra mussel spread in Illinois. This information will be correlated in the Geographic Information System with collections records of native mussels to predict communities of native mussels that are most threatened by the zebra mussel.

Zebra mussel growth in the Illinois River
D. Schneider, R. Sparks, J. Stoeckel, S. Madon
INHS 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.

Suspended sediment effects on mussels
D. Schneider, R. Sparks, J. Stoeckel, S. Madon
Researchers are evaluating 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.

Determining zebra mussel metabolic rates
S. Madon, D. Schneider, J. Stoeckel, R. Sparks
Measurements of metabolic rate are vital to studies of 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. Survey scientists employ this technique to determine metabolic rates and oxygen demand of zebra mussel populations in the Illinois River.

Invasive potential of round gobies
D. Soluk, W. Resetarits
The spread of round gobies from the Great Lakes into tributary streams and connected watersheds should be a focus of great concern. Preliminary experimental studies of growth and thermal tolerance indicate a potential for the gobies to occupy both coldwater and warmwater stream systems. Ongoing studies suggest potential impact of round gobies on streams is high, especially for populations of other smaller benthic fishes (e.g., darters) which may be displaced or directly consumed by gobies. Research focuses on quantifying current range of goby 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 predation by common carp
F. Cronin, J. Tucker, D. Soergel
INHS researchers examined gut contents from 31 common carp collected at Mississippi River Mile 217 in August 1995 for evidence of predation on zebra mussels. We found between 1 and 407 zebra mussel beaks in 83.9% of the fish we examined. For all fish examined, common carp contained 118.2 beaks per fish or about 59 zebra mussels per fish. We found that large fish tend to prey more on larger zebra mussels than do small fish. These preliminary results clearly demonstrate the ability of the common carp to prey on zebra mussels. Considering that common carp are numerous in the Illinois and Mississippi rivers, they may have had an effect on zebra mussel demographics.

Daphnia lumholtzi in the Illinois River
J. Stoeckel, L. Camlin, K. Blodgett, R. Sparks
Daphnia lumholtzi, a zooplankter from Asia, Australia, and Africa and a potential pest, recently invaded the Illinois River. Population trends and densities of the species in the Illinois River resemble those reported in lakes and reservoirs of the southeastern United States, suggesting D. lumholtzi adapts to lotic as well as lentic systems. Daphnia lumholtzi have already entered the Mississippi River via the Illinois River. Because the Illinois River is connected to Lake Michigan, it is likely that this species will soon invade the Great Lakes by upriver transport in the bilge water of commercial and recreational watercraft.

Illinois River zebra mussel veligers
J. Stoeckel, L Soeken, K. Blodgett, R. Sparks
In 1995, pulses containing 50-80 million veligers per second drifted past river mile 121.1 near Havana, Illinois. In July, research ers followed a larval cohort as it drifted downriver and determined its average growth rate to be 6.72 meters per day. Using this growth rate, combined with flow data obtained from the Illinois State Water Survey, INHS scientists calculated that larvae produced in the main channel of the Illinois River travel a minimum of 190 miles before settling. Establishment and growth of zebra mussel populations in the upper Illinois River are strongly dependent upon the size and health of upriver "source" populations in Lake Michigan and the Des Plaines and Kankakee rivers.

Exotic zooplankton in Illinois
C. Kolar, J. Boase, D. Wahl
Exotic species lack natural predators and other population control mechanisms found in th