Illinois Natural History Survey - University of Illinois


Kaskaskia, Ridge Lake, and Sam Parr Biological Field Station Research








Foraging of Juvenile Crappies: the difference is black and white

S.R. Andree and D. H. Wahl

Conditions during early ontogeny can have substantial effects on survival and recruitment of fishes. Overwinter survival during the first year of life is highly dependent on body size, and often represents an early bottleneck for juvenile fish populations. In turn, growth tends to be affected by foraging behaviors, which may be influenced by environmental and biotic variation. For crappies in particular, previous research indicates that turbidity tends to influence growth and abundance, but the strength and direction of these effects differs between species, and factors contributing to this evident relationship between turbidity and growth remain unclear. We are conducting controlled experiments in aquaria that attempt to test the hypothesis that foraging behaviors (i.e. total prey consumption, prey size selection, and prey type selection) are affected by turbidity levels, and that these effects differ between species. The aim of these experiments is to determine whether differences in foraging behavior and success, particularly during a critical early life stage, appear to be a driving force behind observed differences in growth and abundance of adult crappies.


Comparison of mouth morphology and maximum prey size selection among three esocid taxa

T.M. Detmer and D.H. Wahl

Aquatic organisms, especially fishes, exhibit exceptional diversity in mouth morphology and this variation has been shown to influence foraging patterns.  Using laboratory and field experiments we examined the role of differences in mouth morphology on predatory activity in three closely related esocids.  Although predator mouth width predicted most of the variation in maximum prey size, the best predictor of maximum prey included mouth width, taxon, and interaction between the two indicating that behavior, even in closely related species, influences prey size selection.  Information comparing prey size selection among esocid taxa is useful for understanding how to manage esocid populations based on system specific prey characteristics and also for understanding how variations in morphological characteristics of apex predators can influence prey vulnerability and ecosystem structure.


General patterns of zooplankton abundance and community structure in nearshore and offshore habitats of temperate reservoirs

T.M. Detmer and D.H. Wahl

Nearshore and offshore community structure are being examined in fifteen reservoirs of the central portion of the United States.  In addition to relative location nearshore versus offshore, zooplankton abundance and community structure are also influenced by season as well as the presence of gizzard shad.  Evidence presented in this study suggests that zooplankton community structure and abundance in nearshore areas differs from offshore areas and that nearshore areas are likely important in their contribution to total abundance and community structure in reservoirs.


Plasticity of zooplankton size frequency distribution influences the strength of trophic cascades in experimental freshwater communities

T.M. Detmer and D.H. Wahl

The concept of trophic cascades indicates that primary producers and top predators are linked and therefore changes at either the top or bottom of the food web will domino through the food web causing a change in the other.  The evidence in trophic cascades suggests, however, that trophic cascades caused by changes in top predators is less predictable than a direct link would suggest.  The present study uses an experiment with mesocosms to determine if diversity in size frequency distribution of zooplankton communities results in compensation of the reduction of zooplankton biomass because of an increased ratio of P/B in zooplankton resulting from size selective activity from predators.


Longitudinal zooplankton profile in reservoirs

T.M. Detmer and D.H. Wahl

Several studies have indicated that the spatial distribution of zooplankton in reservoirs differs from lakes because a gradient of abiotic conditions often develops from where the river enters the reservoir to the dam.  Because of logistical constraints, few studies have evaluated whether there is a pattern of a peak in zooplankton biomass mid-way between the dam and river as is predicted.  This study evaluates at a higher resolution than has ever been attempted in a reservoir whether there is a pattern in zooplankton that follows the gradient of abiotic conditions from dam to river. 


Examining Habitat Selection in Largemouth Bass

J. J. Craft and D. H. Wahl

Habitat structure within the littoral zone can have an important influence on largemouth bass growth and survival. There have been several studies examining how specific vegetation or woody debris characteristics may affect foraging efficiency and other behaviors; however there is little information comparing effects between these two habitats. We are conducting experiments to determine whether or not largemouth bass display a preference for vegetation over woody debris, as well as how different habitat types may affect predation risk and growth. Results of these experiments will have implications for habitat management practices in systems concerned with largemouth bass recruitment.


Effects of competition on growth of juvenile Black Crappie and White Crappie

D.M. Bogner and D H.Wahl

Water quality can greatly affect the recruitment of fishes as well as the species make up of lakes. In lakes where Black and White Crappie are sympatric one species tends to dominate. Anecdotal evidence suggests that White Crappie dominate in more turbid systems while Black Crappie dominate in clearer waters. Previous experiments have reported conflicting findings as to whether or not crappie are affected by turbidity. We are conducting experiments in controlled mesocosms to evaluate how growth is affected by elevated nutrients and elevated sediments between these two species at the juvenile stage. In addition, we are analyzing a suite of biotic and abiotic factors on multiple lakes to identify any potential factors that might influence crappie composition in lakes other than turbidity.


Examining the effects of biotic and abiotic variables on crappie recruitment

J.A. Garavaglia, M.J. Diana, and D.H. Wahl

Management of crappie populations has been hindered by highly variable recruitment. Often, environmental variables will set recruitment at a particular life stage. Recruitment is affected by any variable that changes reproductive success, survival, or growth and these can change through different life stages. Since there are a number of possible variables affecting recruitment, determining which are controlling factors is extremely difficult.  We are conducting a multi-lake, multi-year study to more precisely determine the environmental variables driving crappie recruitment. We will be monitoring multiple lakes for all life stages of crappie, as well as a number of environmental variables. We are also using telemetry gear to assess movement of adult crappies, while utilizing side scan sonar technology to analyze habitat. Ultimately, a better understanding of the variables controlling crappie recruitment will allow for improved management of the species. 


Using power plant cooling reservoirs and largemouth bass as models to study the effects of anthropogenic inputs and climate change on fish ecosystem.

D.P. White and D.H. Wahl

One of the most hotly debated topics in the current scientific literature concerns global warming and climate change, and its effect across different ecosystems. Currently nuclear and coal-fired power plants throughout the US and abroad utilize water from large reservoirs to cool reactors, creating large bodies of water that are artificially heated above natural temperatures. To examine the possible effects of forecasted climate change on lakes, we will collect data from power plant lakes receiving artificially heated effluent to unheated lakes of similar size, with similar species composition, and location within Illinois. We will examine differences in a number of biotic and abiotic variables. We are using these artificially heated reservoirs as a way with which to understand adaptive plasticity of fishes to global climate change, using largemouth bass as a model.  We are investigating physiological adaptations (e.g. growth rates, bioenergetics) and the genotypic changes that drive them, as well as identifying population structure and ecological niche changes as a result of anthropogenic inputs. With this information, we can make predictions about how global warming might affect largemouth bass and lake ecosystems, and suggest management techniques to maintain aquatic resources under these changing conditions.


Evaluating growth, survival, and physiological differences among juvenile crappies:  Implications for stocking and management using blacknose crappie

J.P. Gring and D.H. Wahl

Although stocking of crappies is not historically widespread, it has recently gained popularity for managing populations in systems with poor recruitment and/or high harvest rates.  Anecdotal evidence suggests that blacknose crappie, a phenotypic variant of black crappie (Pomoxis nigromaculatus) used for stocking, grow and survive better than black crappie in hatchery environments.  The objectives of our study were to compare growth and survival of black, white, and blacknose crappies.  To make these comparisons, we conducted laboratory bioenergetics studies and an experimental pond comparison of growth.  We compared age-0 growth and survival of black, white (P. annularis), and blacknose crappies in 0.04-ha experimental ponds using a common garden approach.  Throughout the three-month experiment, a suite of variables was measured in each pond in order to associate between-pond variation in growth rates with environmental conditions.  In the laboratory, we evaluated metabolic rate, maximum daily food consumption, relative growth rate, and food conversion efficiency of juvenile black, white, and blacknose crappies across a range of temperatures.  These two studies will aid in understanding growth differences among juvenile crappies, as well as the potential causes (e.g. physiological or behavioral differences, etc.).  Understanding differences in growth and survival among black, white, and blacknose crappies at the juvenile stage will aid in managing crappie populations and addressing issues of stunting and/or poor recruitment.


Investigating Effects of Physical Habitat on Secondary Production in Freshwater Lakes

C.S. DeBoom and D.H. Wahl

Understanding the mechanisms that affect the flow of energy and matter through ecosystems is essential for the restoration of degraded habitats as well as the protection of existing natural resources. In lake ecosystems, watershed and basin characteristics have been found to be important factors that influence trophic dynamics, rates of decomposition and nutrient cycling. Recently studies have found strong effects of changes in the physical structure of the littoral zone on ecosystem productivity. While empirical evidence supports an important influence of physical structure on functions of lake ecosystems, mechanisms behind these influences are poorly understood, hindering development of policies to protect habitat. We are examining the mechanisms by which physical habitat influences food web characteristics of lake environments at multiple spatial scales. These objectives will be accomplished through manipulative and observational studies incorporating detailed analysis of trophic networks constructed using both detailed diet and stable isotope approaches.


Establishment of Daphnia lumholtzi in Illinois
M.A. Nannini, C.S. Kolar, and D.H. Wahl
The exotic zooplankter, Daphnia lumholtzi, has invaded a number of lakes in Illinois. Studies conducted by INHS scientists have determined that D. lumholtzi has a competitive advantage over native Daphnia spp. by avoiding predation by young bluegill. At present, long-term effects of this exotic species on aquatic ecosystems in Illinois are unknown. To assess potential changes in zooplankton communities, researchers are examining data from Lake Springfield that characterize the lake before and after establishment of D. lumholtzi. In addition, food habits of planktivorous fish are being examined to assess the contribution of D. lumholtzi to fish diets before and after their introduction. Results of these investigations will help quantify changes that have occurred as a result of the establishment of D. lumholtzi in Illinois waters.


Examining evidence for behavioral syndromes in largemouth bass
M.A. Nannini, J. Parkos, and D.H. Wahl
Behavioral syndromes are characterized by individuals expressing correlated suites of behaviors across different contexts. We have found previously that behavioral syndromes have the potential to play a role in the ontogenetic diet shift of juvenile largemouth bass when switching to piscivory.  We are examining whether behavioral syndromes can effect juvenile largemouth bass growth and survival under different prey resource availabilities. If the behavioral syndrome of individual bass does influences their diet, it should provide insight into how individuals manage important tradeoffs and how these behavioral tendencies may structure the evolution of a population under different environmental parameters.


Comparison of AC and DC electrofishing

M.J. Diana and D.H. Wahl

In order to assess sportfish populations and compare populations across Illinois, it is critical to use standardized gears that are efficient in collecting the targeted fish species.  Standardized practices for population assessments in Illinois have traditionally been AC shoreline electrofishing.  Alternative electrofishing gears using direct current have become more popular recently due to perceived greater efficiency for certain species of fish.  There is a need to evaluate how catch rates vary between the AC and DC electrofishing in order to compare historic data if gear changes are made.  We have been comparing AC and DC electrofishing gears in 15 lakes in spring and fall sampling. Largemouth bass catch rates were very similar between gear types for young-of-year fish, but this was not the case for larger largemouth bass which had greater CPUE with DC electrofishing.  We also observed increased catch rates for common carp using DC gear.  These data suggest that DC gear may work better with larger fish that can generally escape the AC electric field prior to being netted.  Crappie catch rates were low using both gears and electrofishing may not be a good method for evaluating their abundance.  We will continue to conduct AC and DC sampling and future analyses will focus on other species and the size of fish that are captured.  We will use these analyses to make recommendations for comparing catch rates between gears and recommend what gears biases may be expected when targeting certain fish species.


Evaluation of the largemouth bass stocking program

M.J. Diana and D.H. Wahl

Although largemouth bass are stocked extensively, little is known about the long-term contribution of hatchery fish to the natural population. Factors that influence stocking success include prey availability and predation or abiotic factors such as water temperature and water level. We have examined survival and growth of stocked largemouth bass and observed low survival of stocked fish resulting in little to no contribution to the fishery.  Despite this low survival, we have found stocked fish do contribute to reproduction using genetic markers.  We have evaluated multiple techniques in an attempt to increase survival in stocked largemouth bass including comparisons of different sizes of stocked fish, raceway versus rearing pond reared fish, and point source stocked fish (boat ramp) versus fish dispersed into habitat around the lake.  These techniques resulted in little long term increases in survival.  We are currently examining the benefits of training hatchery fish on natural prey prior to stocking to increase the ability of these fish to forage once released.  We are conducting laboratory and pond experiments using hatchery fish acclimated to fathead minnow and bluegill prey and comparing feeding efficiency, growth, and survival with pellet reared fish.  From these studies we hope to generate a better understanding of the use of stocking to supplement largemouth bass and develop alternative stocking strategies.


Evaluation of sportfish regulations used in managing fish populations

T.M. Detmer and D.H. Wahl

A variety of management regulations are utilized to promote quality fisheries, however, success is rarely evaluated.  We have been evaluating regulations throughout the state of Illinois by compiling a database of hundreds of lakes and utilizing IDNR sampling and creel data to compare populations of fish under different management regimes.  Thus far we have focused on largemouth bass regulations, and have begun to expand these question to crappie.  Recommendations will be made regarding which regulations have long-term benefits to a fish population and if harvest rates are high enough to make a regulation effective.


Examining vegetation management practices and their influence on largemouth bass recruitment

M.J. Diana and D.H. Wahl

Aquatic vegetation is essential habitat for largemouth bass and has direct influences on growth and survival.  However, vegetation is often managed with the goal of providing boating or fishing access and little is known about how these practices influence largemouth bass recruitment.  We have continued to conduct habitat manipulations in a number of lakes in an attempt to enhance largemouth bass populations.  Lake Paradise is a water control lake near Mattoon, IL with a vegetation community has been historically been dominated by water willow in low densities.  We are evaluating the potential of planting multiple species of vegetation to promote better largemouth bass recruitment in the lake. We planted different species of vegetation in a variety of sizes of cages in order to prevent common carp from influencing plant growth and survival.  We are evaluating vegetation growth and survival as well as invertebrate and fish communities associated with different cage types. Management recommendations on cage construction and species of vegetation that can be planted will result.  We will assess use of vegetation planting as a tool used to promote largemouth bass recruitment.  We continue to evaluate vegetation plantings at Lake Paradise, drawdown and rotenone efforts at Dolan and Woods Lakes, and vegetation removal through chemical treatments at Airport and Stillwater Lakes.  We have observed no changes in adult largemouth bass density in vegetation treated lakes, but have also found a decline in young-of-year largemouth bass.  Decreased survival of young-of-year may lead to declines in adult populations.  We will continue to follow vegetation treatment lakes and assess changes in largemouth bass populations.  We have also also been measuring vegetation density and cover in 11 lakes and evaluate how largemouth bass populations vary among different vegetation types, cover, and fluctuations in vegetation.  We have been evaluating side scan sonar mapping techniques for use in quantifying vegetated cover.


Factors effecting bluegill population size structure

S.F. Collins, M.J. Diana, J.E. Claussen, D.P. Philipp, and D.H. Wahl

Stunted bluegill populations are viewed as a major problem by many Illinois anglers. 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. We categorized Illinois bluegill populations based on adult size structure using existing creel surveys and standardized sampling to determine which factors are controlling size structures in each of these populations. We then developed an adaptive management experiment to assess the ability of several management alternatives (regulations, predator manipulations) in altering bluegill size structure towards larger individuals. The management experiment is divided into four treatments across 32 lakes in Illinois. The four treatments consist of a control, an 8-inch minimum bluegill size limit, largemouth bass stocking, and a combination of the latter. We plan to use the results from this experiment to make management recommendations on how to improve stunting in bluegill populations. 


Influence of tournament angling pressure on largemouth bass populations

M.J. Diana and D.H. Wahl

Angling tournaments are becoming increasingly popular and although most tournaments practice live release, there can be high delayed mortality or a variety of sub-lethal impacts on individual fish.  Previous research has focused on measuring and reducing the stress on individual fish caught in tournaments, but little work has focused on the effect of these practices on the entire fish population.  We are assessing tournament activity and largemouth bass populations in a number of lakes in Illinois.  Larger lakes tended to have larger tournaments with a higher number of participants, but lake size was not related to total tournament pressure.  We did not detect any changes in abundance or size structure of largemouth bass vulnerable to tournament angling (> 355 mm) or production of young-of-year fish related to tournament pressure.  Non tournament lakes had higher abundances of young-of-year largemouth bass and fewer large fish, but these differences were not significant.  We will continue to collect tournament and largemouth bass population data on these lakes and add additional lakes to this analysis to further understand the influence of tournaments on largemouth bass populations.


Influence of tournament angling during spawning on largemouth bass in Ridge Lake

M.J. Diana and D.H. Wahl

We are conducting experimental tournament angling on Ridge Lake in order to determine how tournaments can effect reproduction, abundance, and growth of largemouth bass.  We have alternated years of closed spring fishing with years of spring angling tournaments and monitored largemouth bass populations.   We have conducted 3 years of spring tournaments while fish were on the nest and compared the changes in the fish population to 6 control years with no tournaments.  So far, we have observed no consistent differences in young-of-year production or adult abundance for largemouth bass related to tournament activity in the spring.  We will continue to alternate tournament and no tournament years to further evaluate the potential effects of tournaments on lake wide recruitment.


Long-term monitoring in Lake Shelbyville

T.M. Detmer and D.H. Wahl

Long-term data collection is important for detecting large scale temporal trends. In addition, these samples can be valuable for use as pre-data in evaluating the effects of a disturbance. We have been collecting data from Lake Shelbyville since the 1980's and are currently using this data set for answering and developing new research questions. All of the data is collected at fixed sites throughout the lake at regular time intervals. Variables that are being sampled include adult and juvenile fish assemblages, zooplankton, invertebrates, water level, and nutrients. In the future we will continue to develop this long-term data set in order to gain a better understanding of the interactions among measured variables and the factors determining community structure in this important reservoir system.  In addition, concerns regarding the sportfish populations in Lake Shelbyville have been identified by anglers and lake biologists.  We are using our long term database coupled with IDNR data to evaluate the sportfish populations of a variety of fish species and identify fluctuations in the population and potential decreases in abundance or size structure.  We will determine how climate change, siltation, and human induced changes have led to changes in the fish communities and how they compare to those of natural lakes.  We will develop recommendations based on these findings to improve the fishery of Lake Shelbyville. 


Long-term trends in angling creel data in Ridge Lake

M.J. Diana, B. Trushel, and D.H. Wahl

Ridge Lake Biological Station is an INHS run facility which is open to the public for fishing. This lake has had a complete creel conducted on all fish caught since its impoundment in 1942. This data set provides a unique opportunity to study the trends in angling such as catch rates and harvest rates as it relates to the status of fish populations, weather, and angler preferences.  Creel data also includes information on individually tagged bass and diet information for both largemouth bass and muskellunge.  This information will allow us to test numerous hypotheses regarding factors influencing angling success and make management recommendations regarding the use of creel data.


Angler Opinion Shift in Response to Changes in the Bluegill Community in Ridge Lake, Illinois

M.D. Diana, J.B. Maxwell, and D.H.Wahl

The use of restrictive fishing regulations in order to enhance bluegill populations is a fairly uncommon and controversial practice. Angler surveys allow managers to assess angler opinions on various regulations, but they only give us a snapshot of current angler opinions. The result is limited information available to determine how angler opinions change over time, specifically how they change in response to fish population changes.  We conducted surveys of angler opinions of restrictive bluegill regulations in years with differing bluegill catch rates.  Abundance of legal (>8” bluegill) varied in the survey years from Low in 1998, High in 2004/2005, and None in 2013.  Our objective was to determine how angler opinions regarding regulations changed over time and how opinions related with angling success. Angler support for an 8” minimum length restriction increased from periods of low catch rates of large bluegill too high support levels during high catch rates, but decreased when bluegill populations declined. Angler support levels for a catch and release season during the bluegill spawning season were high across all survey years regardless of catch rate. Conversely, support for extended catch and release seasons and fishing closures had low support across all survey years. Angler support for a 10 fish daily bag limit has increased from low catch rates of large adult bluegills to high catch rates and has maintained these levels through the bluegill population crash. Information on temporal angler opinion changes in response to regulation effects on fish communities will allow mangers to better develop, maintain, and adapt current fishing regulations to better suit the fishery.


Foraging behavior of larval and juvenile alligator gar

S.E. Butler, L.M. Einfalt, and D.H. Wahl

The alligator gar (Atractosteus spatula), one of the largest freshwater fish in North America,historically occurred in portions of central and southern Illinois, but has been extirpated from the state due to habitat loss and overfishing. The Illinois Department of Natural Resources (IDNR) has begun reintroducing alligator gar into some areas of their native range within Illinois. There is a substantial lack of information on alligator gar biology, particularly for the larval and juvenile life stages. The early life stages of many fish species are critical transition periods, during which important diet shifts and changes in foraging behavior occur. These transitions have important implications for growth and survival of young fish to later life stages. Understanding the food habits of young-of-year alligator gar, the pattern of diet shifts that accompany growth and development in this species, and the behavioral mechanisms underlying these transitions, will fill important gaps in knowledge about the biology of this species. Experiments are being conducted in the laboratory to determine prey selection and foraging behaviors across a range of alligator gar sizes. Data from this study will be useful for determining appropriate prey types to be maintained in rearing ponds, and will help biologists working to conserve alligator gar populations to understand factors that influence growth and survival of larval and juvenile alligator gar in the wild.


Foraging behavior of muskellunge Esox masquinongy as influenced by simulated light intensity, habitat complexity, and prey type

L.M. Einfalt and D.H. Wahl

Numerous abiotic factors can influence the foraging behavior of piscivorous fish.  Esocids are thought to be diurnal foragers that locate prey by sight, but tracking studies often show activity at low light levels.  In laboratory experiments, we will examine the effect of light intensity and habitat on behavior of muskellunge foraging on two prey species, bluegill or golden shiner, that differ in morphology and behavior.  Very little information is known on foraging behavior of muskellunge at differing light levels and potential interactions with presence of habitat.  Results from this study will be compared to a previous study examining foraging by walleye, a species adapted to foraging in low light conditions.  This comparative approach between piscivores that differ in behavior and morphology will allow for a better understanding of adaptive foraging behavior in response to a variable environment.


Hypoxia effects on foraging behavior, ontogenetic diet shifts and growth rates of juvenile largemouth bass

C.G. French and D.H. Wahl

Juvenile largemouth bass go through ontogenetic diet shifts as they mature. They start out foraging on zooplankton then switch to benthic macroinvertebrates and finally once they are big enough, to fish. During the summer, many lakes contain areas of hypolimnetic hypoxia. Fish are known to actively avoid these areas of hypoxia; however there are cases where fish will go into these areas to forage. Our research is aimed at exploring how juvenile largemouth bass respond to hypoxic zones, specifically examining their foraging behavior in relation to their diet shifts. By setting up stratification tanks in our laboratory, we can simulate hypoxic lake conditions to observe foraging behavior at varying oxygen levels. The same simulation will be set up in experimental ponds. Using this data we will be able to determine the influence of hypoxia on foraging behavior, ontogenetic diet shifts and growth rates of juvenile largemouth bass. We will also be able to incorporate oxygen effects on metabolic rates into bioenergetics models for the largemouth bass.


Developing and evaluating a population-specific and range-wide muskellunge bioenergetic model

M.H. Wolter and D.H. Wahl

Temperature is considered to be paramount to growth of ectotherms as it dictates essentially all physiological processes. Growth rates amongst latitudinally distinct populations or stocks of fish have been shown to be adapted to specific thermal regimes and thermal history groups of fish are being increasingly taken into account to maximize growth rate and survival of sportfish. Populations of muskellunge have been shown to be physically and genetically separated by major river drainage into stocks and populations that occur across a gradient of thermal environments. Despite this growing interest among managers and researchers in a finer population-scale classification of muskellunge that recognizes the importance of thermal history, many management tools lag behind. Our objective was to create a population specific muskellunge bioenergetic model as well as a range-wide muskellunge model incorporating multiple populations from varying latitudes. We then conducted simulations and field trials under varying climatic scenarios to explore the influence of thermal environment on growth of different muskellunge populations.


Effects of aeration on overwinter survival and growth of largemouth bass

E. Giebelstein, M.A. Nannini, K. Ostrand, M. Siepker, D.H. Wahl

Overwinter survival of fishes is often a concern in shallow Illinois reservoirs and ponds.  In these situations, aeration is often employed to oxygenate anoxic areas and to increase habitat for fishes.  We stocked largemouth bass into aerated and unaerated ponds to compare growth and survival.  Understanding the benefits and detriments of aeration on fish growth and survival is important for making pond management recommendations


Laboratory assessment of food consumption and metabolic demand of juvenile bluegill (Lepomis macrochirus).

T.J. Holda, L.M. Einfalt, and D.H. Wahl

Bioenergetic models are a popular tool useful for making predictions of consumption and growth. While much research has focused on obtaining input parameters for respiration and food consumption components of a model, often accurate data is lacking, and "borrowed" rather than actual values are often used for model parameters.  At all year classes, planktivorous bluegill regulate food webs, but especially the young-of-year cohort that competes with other juvenile fish in the littoral zone. Thus, bluegill are often used in modeling applications, but current models, such as the Wisconsin bioenergetics model, use data obtained from adult bluegill (>100 mm).  Metabolic rates can differ between sizes in fish, especially between juveniles and adults.  To provide more reliable data for modeling applications, we will determine food consumption, metabolic rate, and SMR for juvenile bluegill between the sizes of 10-80 mm TL.


Morphological differences between bluegill populations in lotic and lentic systems

M.R. Harrington, M.J. Diana, and D.H. Wahl

Bluegill inhabiting littoral and pelagic habitats in lakes display differing morphological characteristics that affect feeding efficiency and vulnerability to predation.  We hypothesized differences in available prey, predators, cover, and other abiotic variables between lotic and lentic systems could cause substantial morphological variation among bluegill populations. We are measuring morphological characteristics of fish size (e.g. total length, body depth, caudal peduncle depth) and individual characteristics of feeding morphology (e.g. gape width, fin length).  The morphological variations between lotic and lentic bluegill may influence foraging, predator avoidance, and mating success.


Individual-based model for walleye
T.L. Galarowicz, D.H. Wahl, and R. Herendeen
Size-dependent mechanisms and physical factors influence fish growth and population dynamics. Individual-based models, which follow individuals of a species rather than an "average" individual, provide additional insight into these relationships. By modeling foraging, daily growth and mortality using an individual based approach we hope to predict growth and survival of young-of-year walleye. Parameters for the model are based on extensive field data and laboratory foraging experiments.


Predictive model of juvenile gizzard shad abundance for Lake Shelbyville, Illinois
T.B. Smith and D.H. Wahl
Gizzard shad dominate the fish communities and are the primary diet item of most piscivores in Midwestern and Southern reservoirs in the continental US. We recently devised a model to predict the annual abundance of gizzard shad in a flood control reservoir from characteristics of spring water-level rises. For the past three years, this model has provided successful a priori predictions of juvenile gizzard shad abundance. These results demonstrate the utility of water level manipulations as a tool to regulate trophic dynamics in systems with managed flows.


Top predators regulate both rooted and pelagic primary producers through crayfish assemblages in shallow aquatic systems
T.B. Smith and D.H. Wahl
Linear food chain models such as the trophic cascade hypothesis (TCH) state that top predators reduce the abundance of grazers and thus indirectly regulate primary producers. Pond habitats contain many violations of linear food chain models including omnivory, spatial subsidies between habitats, and predator-resistant taxa. Despite these complexities, we have shown that predator fish in ponds indirectly increase the abundance of rooted plants and reduce phytoplankton by removing omnivorous crayfish. Our results contrast with the TCH model by demonstrating that predator effects are enhanced by the reduction of nutrients cycled by crayfish from the benthos into the water column. Additionally, many of the indirect effects we observe from predation on crayfish appear similar to indirect effects resulting from predation on planktivorous fish. This research adds to the list of top-down and bottom-up mechanisms that stabilize macrophyte abundance when large predator fish are abundant in shallow aquatic systems.





Predator Recognition, Alarm Response, and Anti-Predator Behavior in Juvenile Asian Carp

J.C. Wilson and D.H. Wahl

The identification of risks, as well as physiological needs often dictate behavioral decisions made by individuals, and prey species are often forced to assess predation risk when making decisions about foraging and reproduction strategies.  Fishes are often exposed to a variety of methods to inform them of an impending predation risk, whether it be through chemical olfaction, visual, or cultural stimuli.   During early ontogeny, Asian carp are exposed to a large variety of predators and selected over native prey fishes.  It is therefore prudent to understand the mechanisms that an invasive prey species utilizes in predator recognition and avoidance behavior when interacting with native predators.  Management of other species (such as sea lampreys and char) often uses specific cues to divert or disrupt migrations and spawning events.  Successfully using alarm cues as a means of control to mitigate the movement and spread of Asian carp is therefore contingent on understanding how specific chemical cues inform behavioral strategies.


Effects of Asian carp on the larval stage of native fish

C.M. Fletcher and D.H. Wahl

Following their introduction into the Mississippi and Illinois River systems, evidence shows that Asian Carp effectively reduce the abundance of zooplankton within these systems.  Recent studies suggest that exploitative competition between Asian Carp and native planktivores occurs at the adult and juvenile stages; however, little is known from controlled manipulative experiments about their effects on the early life stages of fishes, especially native non-planktivorous fish with larval stages relying on zooplankton.  Prey availability during the larval stage of development is a critical determinant of recruitment variability and early stage growth.  We are exploring the potentially complex interactions between Asian carp, native larval fish, and their zooplankton prey using controlled mesocosms and ponds.  Through these studies we will be able to better understand the ecological effects of these pertinent invaders, preparing us for future expansions and invasions. 


Growth and diets among larval Asian carp in the Illinois and Wabash rivers. 

C.M. Fletcher and D.H. Wahl

With the movement of Asian Carp into Illinois waters, there are many ecological interactions that need to be studied in order to fully understand the impact that these invasive fish are having on the natural ecosystem.  While they are well studied in their native range, Asian Carp, and the threats they pose to US waters, have yet to be completely understood.  Spawning, growth rates, and diets have known to vary among the different rivers in Illinois, thus our objective is to analyze and compare otoliths and gut content from larval Asian Carp collected in both the Illinois and Wabash rivers.   Through these comparisons we can better understand the conditions required for successful recruitment and growth and Asian Carp response to unfavorable conditions.  


Evaluation of gear efficiency and detectability of Asian carp in the Illinois Waterway

S.E. Butler, M.J. Diana, S.F. Collins, J.A. Freedman, and D.H. Wahl

Bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix), collectively referred to as Asian carp, are invasive fish species that have become abundant in much of the Mississippi River basin and particularly in the Illinois River.  Biologists are concerned that these species may eventually spread to the Great Lakes through the Chicago Area Waterways System (CAWS).  Multi-agency sampling and removal efforts are currently ongoing in the Illinois River and the CAWS to monitor and control the spread of Asian carp.  A variety of traditional sampling gears (electrofishing, gill nets, trammel nets) are being employed by various agencies to capture Asian carp, but the relative efficiency of each of these gears, and the amount of effort required to detect Asian carp when they are present in low densities, has not been evaluated.  We are examining the relative efficiency of both traditional and alternative sampling gears (hydroacoustics, midwater trawls, purse seines, trap nets, mini-fyke nets, hoop nets, cast nets, seines) at capturing both juvenile and adult Asian carp.  Modeling the probability of detecting Asian carp with various sampling gears based upon data collected across a range of Asian carp densities, and examining factors that contribute to variation in detection probabilities, will allow for determination of appropriate levels of sampling effort and help improve the design of existing monitoring regimes.  Results of this study will assist Asian carp monitoring and control efforts in the Illinois River and the CAWS, and will contribute to a better understanding of the biology of these invasive species in North America.


Evaluation of the distribution, movements, and habitat use of river redhorse and greater redhorse in the upper Illinois River basin

S.E. Butler and D.H. Wahl

River redhorse (Moxostoma carinatum) and greater redhorse (M. valenciennesi) are large, laterally compressed suckers native to eastern North America.  The river redhorse is currently listed as threatened and the greater redhorse as endangered in Illinois.  A thorough assessment of the range and abundance of these species in the upper Illinois River basin is needed to facilitate conservation efforts in the face of continued urbanization and increasing demand for water resources in this region.  Our first objective is to characterize the distribution of river redhorse and greater redhorse in the upper Illinois River basin by identifying all river segments where these species have been documented and those where they have not been recorded.  This information will aid in the identification of river segments critical to conservation efforts.  Our second objective is to assess movement patterns and habitat associations of river redhorse and greater redhorse during different seasons.  We are monitoring the movements of radio-tagged river redhorse in the Kankakee River to identify habitat elements (spawning, feeding, and overwintering areas) that may be critical to the future conservation of this species.   Ultimately, this research will help biologists understand factors that have allowed these species to persist in some river segments, but have contributed to their extirpation in others.  This will be an important step towards developing recovery plans and eventually delisting these species. 


Evaluation of woody debris as a habitat restoration tool for stream biota: assessment of macroinvertebrate communities
E.L. Effert-Fanta, J. Weidner, H.R. Dodd, and D.H. Wahl
Illinois streams experience flash floods which drastically change the appearance of the stream. As the streams recede back into their banks, deposition of new woody debris takes place, forming complex logjams and snags which are utilized by a number of stream biota. In streams with little or no woody debris, introduced woody structures have been placed into the stream to create habitat for fish and macroinvertebrates. In our study, we are examining macroinvertebrate colonization of introduced woody debris seasonally and comparing this to naturally deposited woody debris. We are also examining the effects of temperature and stream geomorphology on colonization by comparing colonization in four streams in the northern portion of Illinois and four in the southern portion. As part of the Pilot Watershed Program, this study will aide in the evaluation of restoration practices to improve Illinois streams.


Influence of riparian forest on stream community structure and ecosystem function in an agricultural watershed
E.L. Effert-Fanta, R.U. Fischer, and D.H. Wahl
Forested riparian buffers have been shown to improve stream water quality in agricultural watersheds by reducing soil erosion and filtering runoff before it enters a stream. While previous studies have addressed the size of riparian buffers needed to reduce pollutants, more research is needed to determine how riparian vegetation affects the structure and function of stream communities in agricultural regions.  In this study, we are examining agricultural streams with a gradient of riparian forest (92%-16%) to determine the effect of riparian and watershed land use on stream biological communities.  Sampling for this study is being conducted seasonally for three years. Macroinvertebrate and fish biotic metrics will be used to examine community differences related to land use, in-stream habitat, and water chemistry parameters.  In addition to evaluating community composition, differences in stream metabolism among sites will be investigated as an assessment of land use effects on ecosystem function.  Stable isotopes analysis will also be performed to determine how land use and seasonal changes affect energy flow and in-stream food web structure. Results from this study will improve our understanding of stream ecosystems and have direct implications for the future use and management of streams in areas modified by intensive agriculture.


Larval fish monitoring in the Illinois Waterway

S.E. Butler, S.F. Collins, M.J. Diana, and D.H. Wahl

Factors affecting the early life stages of fish strongly affect recruitment to adult populations.  The rapid establishment and continued spread of bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix)in the Illinois Waterway is in part due to their ability to reproduce and for their young to survive under the prevailing environmental conditions found in this system.  Larval and juvenile Asian carp have previously been collected from the lower Illinois River, but the potential for Asian carp reproduction and recruitment in upstream pools of the Illinois Waterway is unknown.  Additionally, recruitment of Asian carp to the juvenile life stages has been found to be highly variable among years in the Illinois River, but factors contributing to this variation are not well understood.  Information on the distribution of larval Asian carp across space and time is needed to identify adult spawning areas, determine reproductive cues, and characterize relationships between environmental variables and survival of young Asian carp.  Larval fish sampling will be used to assess the timing and extent of Asian carp reproduction in the IllinoisWaterway, and may prove to be an early detection method in the Chicago Area Waterway System.  This information may also be useful for designing future control strategies that exploit aspects of Asian carp spawning and early life history. 


Unconventional gear development for Asian carp

M.J. Diana, S.E. Butler, S.F. Collins, J.A. Freedman, and D.H. Wahl

Traditional sampling gears vary widely in their ability to capture Asian carp.  Additionally, the ability of some of these gears to capture Asian carp in the conditions found in the Chicago Waterways is questionable.  We are working with other fisheries scientists and commercial fisheries to develop gears specifically targeting Asian carp in areas of low density and in the deep-draft channels of the Chicago Waterways.  We are evaluating the use of large (2 meter diameter) hoop nets, deep (10 meter) tied-down gill nets, and Great Lakes pound nets for capturing Asian carp in different areas of the Illinois Waterway.  Capture efficiency and size selectivity of these new methods is being evaluated and compared with selected traditional gears to determine the utility of these techniques for monitoring and controlling Asian carp populations.


Habitat value in mid-sized rivers in Illinois

E.L. Effert-Fanta and D.H. Wahl

It is important to quantify habitat in order to fully understand factors that may be limiting to a fishery.  In mid-sized rivers there is not a standardized method for evaluating habitat in Illinois.  Mid-sized rivers can be difficult to sample as they are often too deep to wade, yet too shallow to navigate by boat.  Habitat evaluation is needed for mid-sized rivers that relate these habitat measures to fish populations.  We are conducting habitat mapping using side scan sonar and transect methods to quantify substrate, woody structure, depth, and flow characteristics in the Kaskaskia and Embarrass Rivers.  Habitat targeted electrofishing samples are being used to evaluate fish assemblages and abundance associated with different habitat types.  We observed the highest catch rates over gravel substrate, in wooded habitat, shallower sites, and on the inside bends of the channel.  In particular, crappie were significantly more abundant in wooded sites. 


Nutrient recycling by invasive Asian carp in the Illinois River

S.F. Collins and D.H. Wahl

Consumer-driven nutrient recycling can be an important driver of productivity in aquatic ecosystems.  Fishes alter nutrient dynamics through excretion and egestion. Highly productive invasive fishes such as Asian carp may be having strong effects on nutrient recycling, however such impacts are presently unknown. We are evaluating how the highly invasive and productive Asian carp alters rates of nutrient recycling in large river ecosystems, and whether dense aggregations of Asian carp can elevate nutrient concentrations above already high ambient concentrations in the Illinois River.  Findings will aid in better understanding how the immense productivity of Asian carp is altering nutrient dynamics in large river ecosystems.


Vulnerability of juvenile Asian carp to largemouth bass

E.J. Sanft and D. H. Wahl

Asian carp are highly publicized invasive species throughout the Mississippi River basin. Both species (bighead and silver) are known to reproduce quickly and become some of the most abundant species in the areas they have invaded. The sheer numbers of offspring they are capable of producing can have negative impacts on the environment and there are concerns about the effects they may have if they spread into the Great Lakes. Little is known about why these fish are so successful in establishing themselves in certain locales or how they might be controlled. We are assessing the vulnerability of juvenile Asian carp to predation by native largemouth bass. Experiments will compare vulnerability and anti-predatory behavior of silver and bighead carp to that of common native prey species. These results may provide insight into ways to control and the factors influencing the establishment of Asian Carp.   


Impacts of Invasive Asian Carps on Native Food Webs

J.A. Freedman, S.E. Butler, and D.H. Wahl

Asian carps (bighead carp, Hypophthalmichthys nobilis, and silver carp, H. molitrix) are abundant invasive species in the Mississippi River drainage and in particular the Illinois River. Competition with these invasive carps has caused declines in populations and condition of some native species (including large planktivorous filter-feeders such as bigmouth buffalo, Ictiobus cyprinellus, gizzard shad, Dorosoma cepedianum, and paddlefish, Polyodon spathula).  Impacts on many other species, such as native planktivorous minnows (Cyprinidae) and non-planktivores, however, are largely unknown.  Our objectives are therefore to determine the impacts of invasive Asian carps on native fishes and aquatic food webs.  We are using stable isotope analysis of carbon and nitrogen to compare food-webs at sites in the Illinois Waterway with and without Asian carps, and with historic food-webs.  These data will supplement our ongoing research on Asian carps in the Illinois River, and will help to inform management and conservation decisions in this system.  The potentially catastrophic impact of Asian carps in the Great Lakes has been the subject of much debate and concern. Our proposed study will provide empirical evidence about the impacts of Asian Carps on native food-webs.


Hydroacoustics: a tool for understanding fish-habitat association in rivers
R.M. Claramunt, J.M. Dettmers, D.H. Wahl, D.A. Soluk, and S. Gutreuter
Large floodplain rivers, such as the Mississippi and Illinois, are composed of a variety of different habitats (e.g., backwater, side channel, main channel). The majority of sampling done to understand the importance of these different habitat types to fish occurs outside the main channel because high current velocities. As a result, present knowledge on fish abundances, species composition, and habitat utilization in the main channel is lacking. Through midwater and bottom trawls, we have found that the main channel supports an abundant and diverse fish assemblage. A digital 200-kHz single beam hydroacoustic system is being used to investigate questions such as how do fish survive in high-current velocities that are typical of the main channel? Where exactly are fish located in the main channel? Fish targets have been found to be strongly associated with sand dunes in the echograms from the Mississippi River. However, when dunes are not present (as in the Illinois River), fish targets are more evenly distributed, both vertically and horizontally. Sand dunes may be a critical habitat river fishes that have adapted to the conditions in the main channel of large rivers.


Evaluation of commercial navigation and indirect effects on fish behavior in large river systems
E.J. Gittinger, D.A. Soluk, D.H. Wahl, and J.M. Dettmers
Barge traffic has the potential to directly increase mortality of fishes. Alternatively, fish may exhibit avoidance behaviors and move away from barges in large river systems. If this is found to be true then the costs associated with these behaviors should be evaluated, as well as how an increase in barge traffic may impact the fishes of large rivers. This study is being conducted in reach 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.



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