2025 Midwest Fish & Wildlife Conference

AUTHORS: Connor S. Church, University of Missouri School of Natural Resources; Allison A. Pease, University of Missouri School of Natural Resources

ABSTRACT: In the Central U.S., we are experiencing more frequent extreme high-flow events (floods) in many stream systems associated with climate change. Large swaths of the globe are expected to experience wetter conditions with more frequent, high-magnitude precipitation events in the future. Our objectives were to determine if the effects of extreme flows on fish recruitment are predictable based on life history traits, and to learn how extreme flows affect habitat characteristics and food availability for age-0 fishes. To provide these data, we sampled age-0 fishes by seining in Richland Creek and a side channel of the Lamine River in central Missouri 2023-2024. Each site was surveyed twice monthly from May-September. To characterize food resource availability and quality in relation to flows across the season, we sampled benthic macroinvertebrates using dip net sweeps, and we collected zooplankton using a plankton trap. In 2023, a year with an exceptionally dry spring followed by one summer flood, abundance of age-0 native fishes was low in the Lamine River side channel compared to Richland Creek, Western Mosquitofish, an opportunistic species, predominated in 2023. In 2024, two spring floods occurred, along with multiple rain events during the spring and early summer that allowed floodplain and side channel access to spawning fishes and age-0 individuals. Age-0 individuals of periodic species such as longnose gar, bigmouth buffalo, and skipjack herring were only detected in 2024. Aquatic invertebrate diversity and abundance were higher in 2023 than in 2024. Our research will help address how timing, frequency, and magnitude of flow events affect recruitment in stream fish assemblages.

AUTHORS: Braden Lensing, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point; Daniel Dembkowski, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point; Joshua Raabe, University of Wisconsin-Stevens Point; Jason Breegemann, Wisconsin Department of Natural Resources; Daniel Isermann, U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin-Stevens Point

ABSTRACT: Previous research indicates that lake sturgeon Acipenser fluvescens recruitment is limited in the Lower Fox River below De Pere Dam. Habitat enhancements in the form of an offshore reef have been proposed to potentially improve the recruitment of lake sturgeon. However, identifying spawning habitats for other species could help to ensure that restoration efforts for lake sturgeon do not result in loss of spawning habitat for other species. The Lower Fox River supports spawning runs of walleye Sander vitreus and lake whitefish Coregonus clupeaformis, both of which support important fisheries in southern Green Bay. Our objectives are to 1) describe spatial variation in walleye and lake whitefish egg densities in the LFR below De Pere Dam to inform placement of the lake sturgeon spawning reef; 2) determine if spatial variation in egg densities are related to a suite of environmental variables (e.g., flow, depth, and substrate), 3) determine if spatial distributions of eggs are similar for walleye and lake whitefish, and 4) describe the timing (e.g., start, peak, end, and duration) of walleye and lake whitefish spawning. Heat maps generated from relative egg densities illustrate the spatial distribution of walleye and lake whitefish egg densities and reveal significant overlap in egg deposition between the two species, as well as notable overlap with three of four proposed reef locations. The 2023 lake whitefish spawning period spanned 14 days, beginning on November 8 and concluding around November 21. In contrast, the 2024 walleye spawning season lasted 38 days, commencing on March 18 and ending about April 25.

AUTHORS: Jacob L Bentley, The Ohio State University; Stuart A Ludsin, The Ohio State University

ABSTRACT: The intentional introduction of nonnative predators to generate novel fisheries, while common, has the potential to threaten existing fisheries through numerous mechanisms such as competition and predation. Similarly, stocking success could be hampered by these same mechanisms, highlighting the need to understand habitat use and niche overlap among biota. In Ohio reservoirs, Blue Catfish (Ictalurus furcatus) has been stocked since 2010 to create novel trophy fisheries. However, the potential exists that the success of Blue Catfish will either threaten the success of existing fisheries or threaten the success of the stocking program if niche overlap among species is high. To assess niche overlap and the potential for competition among stocked Blue Catfish, native predators (e.g., Channel Catfish, Ictalurus punctatus; Largemouth Bass, Micropterus salmoides), and stocked saugeye (Sander canadensis x S. vitreus), we analyzed the diets and stable isotope ratios (nitrogen, carbon, and sulphur) of muscle tissue from fish collected during spring, summer, and fall of 2021-2023 in two Ohio reservoirs: one stocked with Blue Catfish (Hoover Reservoir) and one not stocked with Blue Catfish (Alum Creek Lake). We hypothesized that niche overlap would be highest between catfish species, with Largemouth Bass and saugeye also overlapping. Our hypothesis was only partially supported. Results show niche partitioning between Blue Catfish and all other species. Blue Catfish consumed more and larger fish prey (e.g., large-bodied Gizzard Shad) relative to all other species, with Channel Catfish feeding mostly on aquatic insect larvae (e.g., chironomids). By contrast, Largemouth Bass and saugeye primarily fed on smaller-bodied Gizzard Shad than Blue Catfish, with their diets being similar as expected. In addition to quantifying niche envelopes for these species, we discuss how our findings, and stable isotopes in general, can be used to help inform stocking decision-making in reservoir ecosystems.

AUTHORS: Kayla Lenz, Great Lakes Indian Fish and Wildlife Commission; Aaron Shultz, Great Lakes Indian Fish and Wildlife Commission; Adam Ray, Great Lakes Indian Fish and Wildlife Commission; Carl Klimah, Mille Lacs Band of Ojibwe

ABSTRACT: Mille Lacs Lake located in the 1837 Ceded Territory in central Minnesota offers a unique site for assessing the movement of fish throughout a large temperate lake. The relative shallowness of the lake and resultant lack of a thermocline allows ogaawag (walleye Sander vitreus) to forage throughout the lake, thus maximizing their range. Ogaawag , have been impacted by the many changes happening in this system over the past several decades, resulting in a variable but overall decreasing population between 1980 and 2016, when the population seems to have plateaued. This decrease has largely been attributed to a decrease in annual recruitment from hatching to age-2, but the root cause of that recruitment problem is yet unclear. In other large lake systems, ogaawag frequently display spawning site fidelity, making them especially reliant on a relatively small spawning area. Disturbances and changes in these areas may decrease overall reproduction and decrease fry survival. Identifying and protecting these critical sites may maintain annual recruitment of Mille Lacs ogaawag. The purpose of this study was to identify ogaawag spawning sites across years, characterize habitat type, and quantify spawning site fidelity of adult ogaawag in Mille Lacs Lake. Here we examine the movements of 70 tagged adult ogaawag during the spawning periods of 2019, 2020, and 2021 to determine the proportion of ogaawag that display spawning site fidelity and which areas of the lake were “hotspots” for spawning. Using an acoustic telemetry array, we examine the relationships between sex, length, detection depth, average residence time at each receiver, and spawning site fidelity to establish patterns of behavior among ogaawag. We found that ogaawag in Mille Lacs display spawning site fidelity at high rates (96%) and identified areas with rocky and/or hard substrate, lots of wind/wave action, and that are near undeveloped shoreline to be hotspots of ogaawag activity during the spawning season. We also observed what is likely an occurrence of skipped spawning in a female ogaa. Findings from this study should be used to create new stewardship plans to protect in-lake, shoreline, and upland habitats near spawning aggregation sites in Mille Lacs Lake. These approaches may be applicable to other large lake ecosystems.

AUTHORS: Jeston Hassler, South Dakota State University; Maxwel Wilkinson, University of Wisconsin-Stevens Point; Quinnlan Smith, University of Wisconsin-Madison Center for Limnology; Joseph Mrnak, Wisconsin Department of Natural Resources-Escanaba Lake Research Station/University of Wisconsin-Madison Center for Limnology

ABSTRACT: In recent decades, some lakes in the Ceded Territory of Wisconsin (approximate northern third of the state) have experienced increasing largemouth bass Micropterus salmoides abundance coupled with declining walleye Sander vitreus abundance. These shifts in abundance have become of management concern, as largemouth bass have been hypothesized to negatively influence walleye populations through potential competitive or predatory interactions. Yet, a mechanistic understanding of these ecological interactions remains relatively unknown. As climate change continues to alter thermal habitat in northern Wisconsin lakes, understanding how warming water temperatures may influence largemouth bass and walleye interactions, specifically their consumption rates of prey items, could assist in the future management of the two species. Thus, our objectives in this study were to 1) calculate diet overlap and consumption rates of common prey items for largemouth bass and walleye in a northern Wisconsin lake and 2) simulate consumption rates of largemouth bass and walleye in predicted climate change scenarios. Our study site, Little John Lake located in Vilas Co., Wisconsin, contains a naturally recruiting walleye population and fish assemblage similar to many other northern Wisconsin lakes. We intensively sampled diets of largemouth bass and walleye in Little John Lake from May-October in 2024 and took a bioenergetics approach to estimate and simulate consumption rates of these species under climate-change scenarios. Increased rates of consumption were apparent for both species, notably of yellow perch Perca flavescens and Lepomis spp., yet walleye consumption rates slowed when water temperature began reaching their thermal tolerance. Understanding how largemouth bass and walleye consumption rates may differ under climate-change scenarios may give valuable insight into future interactions between these species in northern Wisconsin lakes.

AUTHORS: Molly Sobotka;
Jessica Fulgoni;
Ashley Johnson;
Alex Bell


ABSTRACT: Zooplankton link microbial primary producers to larger consumers (primarily fish) in aquatic food webs. Despite their importance, assessment of zooplankton populations in large rivers is rare, especially across large spatial scales and during the winter. We collected zooplankton alongside summer, fall, and winter water quality sampling events in the Upper Mississippi River Restoration Program’s Long Term Resource Monitoring element key reaches during 2019 and 2020. We used generalized additive models to assess the relationships between measures of zooplankton abundance and local and site level habitat variables. Zooplankton abundance was strongly tied to measures of productivity (chlorophyll) and water clarity (suspended solids), but the strength and shape of these relationships was not the same between seasons. Abundance of crustacean zooplankton was greatest during the winter however we did not find a significant relationship between abundance and chlorophyll during that season. Crustacean density and biomass were negatively associated with the presence of invasive carps and positively associated with abundant aquatic plants.

AUTHORS: Zane McAdams, U.S. Geological Survey; Dustin Broaddus, U.S. Geological Survey; Ryan Trimbath, U.S. National Parks Service; Eric Waits, U.S. Environmental Protection Agency; Marc Mills, U.S. Environmental Protection Agency; Alexander V. Catalano, U.S. Army Corps of Engineers; Matthew R. Acre, U.S. Geological Survey

ABSTRACT: The Cuyahoga River watershed was designated as an Area of Concern by the U.S. Environmental Protection Agency in 1987. Of the original nine Beneficial Use Impairments (BUIs), five remain, three of which address water quality, fish population status, and habitat availability. The American Brook Lamprey (Lethenteron appendix; ABL), is a non-parasitic, cold-water species sensitive to habitat degradation and considered an indicator species– presence reflects good habitat quality while absence suggests poor habitat quality. Though widely distributed, population status assessed at the HUC-8 watershed scale are highly variable depending on local conditions. Since 1984, the Ohio Environmental Protection Agency (OEPA) has consistently monitored the Cuyahoga River as part of their standardized sampling to document all fish biodiversity in the river. The first ABL occurrence in the watershed was recorded in 2000 in Salt Run, a cold-water tributary located at river kilometer (rkm) 49 within Cuyahoga Valley National Park. Since then, sporadic occurrences have been documented in Salt Run and Dickerson Run, both cold-water tributaries. In 2023, we recorded the first ABL ammocoete, confirmed through genetic analysis, in the mainstem Cuyahoga River near the confluence with a cold-water tributary at rkm 43. We developed a standardized backpack electrofishing sampling protocol in 2024 to explore potential habitat in the mainstem that may be suitable for the species near cold-water tributaries, including the two known ABL tributaries. We discovered the species at one new location, Columbia Run (rkm 41.2), not represented in historical samples. Two specimens were collected at various metamorphic stages suggesting that recruitment has been occurring near Columbia Run. These findings suggest expansive restoration efforts such as, but not limited to, dam removals appear to be resulting in range expansion of ABL, including into the mainstem of the Cuyahoga River.

AUTHORS:  William J. Radigan, University of Nebraska; Dr. Mark Pegg, University of Nebraska; Christopher Longhenry, South Dakota Department of Game, Fish, and Parks, Dr. Cameron Goble, Alberta Environment and Protected Areas; Dr. Kevin Pope, United States Geological Survey—Nebraska Cooperative Fish and Wildlife Research Unit

ABSTRACT:  Walleye Sander vitreus and Sauger Sander canadensis are both socioeconomically important sportfish species in Lewis and Clark Lake, an interjurisdictionally managed mainstem Missouri River reservoir fishery. Adult Walleye (n=136) and adult Sauger (n=82) movement patterns were assessed from March 2021 to September 2024 among four management zones corresponding roughly to quarters of Lewis and Clark Lake using acoustic telemetry. We used a multistate live-dead model approach to assess survival, detection, and movement probabilities. Walleye survival probabilities (mean 85%) varied over time. Detection (mean 81%) and movement (mean 14%) probabilities varied by zone. Sauger detection probabilities varied by zone (mean 58%), and transition probabilities varied by sex, with female Sauger more likely (mean 14%) to transition among zones than male Sauger (mean 6%). Approximately 34-44% of all Walleye and Sauger were site residents, moving less than 10 km from their tagging location over the study duration. Non-site resident male and female Sauger utilized 44-47 km of the reservoir. Female Walleye utilized more of the reservoir (58 km) than male Walleye (45 km). Walleye tagged near Fort Randall Dam utilized more of the reservoir (69-72 km) than Walleye tagged elsewhere (47 km). Exploitation estimates were derived from angler-reported tags and entrainment estimates were based on detections recorded on receivers placed downstream of Gavins Point Dam. Annual exploitation (0-19%) and entrainment (0-5%) are considerable sources of loss for adult Walleye and adult Sauger in Lewis and Clark Lake. Examination of Walleye and Sauger movement patterns and sources of loss enables fisheries managers to focus management on areas identified to be important for spawning and validates the appropriateness of maintaining current harvest regulations.

AUTHORS: Thomas S. Jones, Minnesota Department of Natural Resources
Mark Luehring, Great Lakes Indian Fish and Wildlife Council
Heidi Rantala, Minnesota Department of Natural Resources
John M. Hoenig, Virginia Institute of Marine Sciences
Patrick J. Schmalz, Minnesota Department of Natural Resources

ABSTRACT: Abundance of Walleye in Mille Lacs Lake, Minnesota, has decreased since the 1990s. Two important environmental changes likely contributed to these declines. First, water clarity increased abruptly in the mid-1990s and increased clarity continues through the present day. Second, zebra mussels and spiny waterflea invaded in the late 2000’s, leading to a 90% reduction in zooplankton. Efforts to rebuild the stock through low harvest since 2013 have met with limited success. This study used multiple approaches to compare Walleye productivity changes associated with three time periods (pre-water clarity, post-water clarity, and post-invasive species). First, we estimated annual harvestable surpluses by summing Walleye fishing mortality and the resultant change in population size estimated from statistical catch-at-age models. These data were fit to surplus production models making various assumptions about the shape of the sustainable yield curve. Second, we estimated total annual Walleye production using an instantaneous growth model. All models showed reduced production after each ecological event. Recognition of reduced productivity may have ramifications for future Walleye management in Mille Lacs Lake.

AUTHORS: Shaley Valentine, Aquatic Ecology Lab, Ohio State University

ABSTRACT: River theory suggests predictable changes in biological resource availability occurs when the river’s physical structure shifts. However, little empirical evidence exists to know if river theories can predict shifts in resource use along environmental gradients and better understand the macrosystem structuring of difficult to study large rivers. Here, I quantified the prey and habitat use of eight native species across space and time using trace element, stable isotope, and diet analyses in the Upper Mississippi River System (UMRS). The UMRS varies in its physical structure from homogenous and complex in the upper reaches to (Pools 4, 8, 13) to physically simple and disparate in the lower reaches (Pool 26, the Open River reach, and the La Grange Pool of the Illinois River), and I expected the resource use of fishes to follow this complexity pattern. At the smallest scale, diets of predatory fishes were homogenous in the physically similar upper reaches. At a seasonal scale, contrary to expectations, resource use breadth increased and isotopic overlap decreased from upstream to downstream. And at life-long scales, fish more often originated from tributaries and other river reaches than the mainstem river moving downstream. Combined, these data suggest that the physical environment of the UMRS affects the habitat and prey use of native fishes. These results follow different riverine theories depending on scale: physically homogenous reaches exhibited similar resource use (Serial Discontinuity Concept) and physically disparate research exhibited stark contrasts in resource use (River Continuum Concept or Riverine Ecosystem Synthesis). Regarding macrosystem structuring, these stark differences suggest the upper and lower reaches of the UMRS have different ecosystem structures and functions and that management of this system should occur at both local and system-wide scales.

AUTHORS: Maxwel Wilkinson, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin - Stevens Point; Stephanie Shaw, Wisconsin Department of Natural Resources, Escanaba Lake Research Station; Joseph Mrnak, Wisconsin Department of Natural Resources, Escanaba Lake Research Station and University of Wisconsin - Madison, Center for Limnology; Greg Sass, Wisconsin Department of Natural Resources, Escanaba Lake Research Station; Daniel Dembkowski, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin - Stevens Point; Daniel Isermann, U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit, University of Wisconsin - Stevens Point

ABSTRACT: The Ceded Territory of Wisconsin is a lake-rich region that supports important tribal subsistence and recreational fisheries for multiple species. Recently, declines in walleye Sander vitreus production and recruitment, coupled with increases in centrarchid abundance (e.g., largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus) have created challenges for managers in terms of maintaining desired fish community structure amidst changing environmental conditions and angler preferences. Competitive and predatory interactions between centrarchid species and walleye have been hypothesized to influence walleye natural recruitment, notably in small lakes (

AUTHORS: Madison Dunlap, Central Michigan University Biology Department and Institute for Great Lakes Research; Daelyn Woolnough, Central Michigan University Biology Department and Institute for Great Lakes Research

ABSTRACT: Unionids (i.e., native freshwater mussels) provide essential ecosystem services to other benthic macroinvertebrates by concentrating nutrients as well as stabilizing substrate. Research has indicated that different unionid species may contribute unequally to ecosystem services which may be particularly important to epizoic macroinvertebrates living on live unionids. This research sought to understand what ecosystem factors or unionid traits contribute to structuring the epizoic assemblage and how epizoic assemblages relate to the larger benthic macroinvertebrate assemblage. Metadata was collected from unionid surveys between 2015-2023 from across the Chippewa River, Michigan USA. Macroinvertebrate and epizoite data, as well as additional data to fill in data gaps from metadata analyses, were collected during the summer of 2024 at 12 Chippewa River sites. Questions we ask include: 1) What macroinvertebrate assemblages are using live unionids as habitat, 2) Do different traits of unionid shells (e.g., smooth, bumpy, size) contribute to different epizoic assemblages and, 3) How does the epizoic assemblage on unionids compare to traditional D-net macroinvertebrate assemblages? This study considered 5 species of unionids. Analyses is ongoing but will include a comparison of epizoite and benthic macroinvertebrate data across biotic and environmental factors, a prediction of the epizoite density and species richness of epizoite macroinvertebrates based on unionid host traits, and a comparison of epizoic assemblage metrics. Overall, we predict that macroinvertebrate epizoic assemblage will differ from the surrounding benthic macroinvertebrate assemblage and will be structured based on unionid traits. Results give insight into how changes in unionid assemblages, like species extinction and declines, may impact ecosystem services and how data on benthic macroinvertebrates can inform this research. This work is the first to quantify epizoic organisms across multiple species of unionid hosts and compare epizoic macroinvertebrate assemblage to the surrounding macroinvertebrate assemblage.

AUTHORS: Joshua Fluur, Southern Illinois University; Gregory Whitledge, Southern Illinois University

ABSTRACT: Walleye (Sander vitreus) is a popular sportfish whose populations are often supported by maintenance or supplemental stocking, with most fish stocked as fry, fingerlings, or advanced fingerlings. Evaluation of stocking efficacy is important to inform decisions regarding fish stocking rates and sizes and allocating hatchery fish to locations where maintenance or supplemental stocking is most needed. Several types of artificial tags or marks can potentially be used to identify stocked fish, but many have various drawbacks. Natural chemical markers in otoliths or eye lenses offer several advantages compared to conventional tags or marks and can be used to identify stocked fish when differences between hatchery-reared and wild fish are present. However, the accuracy of these approaches for identifying Walleye stocked at either fry or fingerling sizes has not been evaluated. Thus, the objectives of this study are to assess identification accuracy for Walleye stocked as fry or fingerlings using otolith microchemistry and eye lens stable isotope analysis. Known stocked fish and fish moved between chemically distinct locations to simulate stocking were obtained from several sources. Results to date indicate that otolith microchemistry can identify Walleye stocked as fingerlings with high accuracy and that the source hatchery signature can be detected in fish stocked as early as three days post-hatch. Results of this study will provide guidance regarding applications of otolith and eye lens chemistry techniques to assess contributions of stocking and natural reproduction to Walleye populations and relative efficacy of stocking fish at varied sizes.

AUTHORS: Tariq Tajjioui, U.S. Geological Survey; Daniel Kelner, U.S. Army Corps of Engineers; Stephen F. Spear, U.S. Geological Survey; Diane L. Waller, U.S. Geological Survey; Trevor W. Cyphers, U.S. Army Corps of Engineers; Joseph W. Jordan, U.S. Army Corps of Engineers; Christopher M. Merkes, U.S. Geological Survey; Colin C. Moratz, U.S. Army Corps of Engineers; Theresa M. Schreier, U.S. Geological Survey; Bernard E. Sietman, Minnesota Department of Natural Resources; Sarah A. Douglass, Illinois Natural History Survey

ABSTRACT: The Spectaclecase mussel (Cumberlandia monodonta) is an endangered freshwater species native to the large rivers of the Mississippi River basin in the Midwest and Southeast United States. To support the conservation of Spectaclecase populations, organizations such as the U.S. Army Corps of Engineers, Minnesota Department of Natural Resources, and Wisconsin Department of Natural Resources are implementing habitat restoration initiatives along the upper Mississippi River (UMR). However, there are few known populations of Spectaclecase in the UMR, and gathering more occurrence data is crucial for effective restoration efforts. Traditional diving methods are typically used for surveying Spectaclecase, but this species’ preference for sheltered habitats, such as large interstitial spaces and crevices, makes these methods risky, costly, and time-consuming. Environmental DNA (eDNA) presents a promising alternative for monitoring aquatic species, although freshwater mussels often yield low detection rates. A quantitative PCR (qPCR) assay for Spectaclecase has previously been developed to detect known populations. Our study aimed to build on this foundation by conducting eDNA surveys throughout the UMR to assess detection rates and locate unknown populations. Between 2020 and 2024, we collected eDNA samples from over 250 sites across 23 pools in the UMR. DNA from the samples was extracted and analyzed using the established Spectaclecase eDNA marker. We also performed dive surveys at any new positive eDNA detection site to confirm the presence of this species. Our findings indicate that eDNA can successfully identify previously unknown populations of Spectaclecase, although locations with documented populations of Spectaclecase sometimes failed to produce positive eDNA detections. Dive surveys revealed that even weak positive eDNA detections were sufficient to locate Spectaclecase mussels. This research highlights the effectiveness of eDNA as a monitoring tool for this endangered species while also addressing the challenges of detecting declining mussel populations in expansive river systems.

AUTHORS: Maddy Siller, South Dakota State University; David Coulter, South Dakota State University; Steven Chipps, U.S. Geological Survey; Mark Kaemingk, University of North Dakota; Taufique Mahmood, University of North Dakota; Matthew Maldonado, University of North Dakota; Michaela Neal, University of North Dakota; Ayon Saha, University of North Dakota; Alison Coulter, South Dakota State University

ABSTRACT: Many studies have documented a corresponding shift in fish communities caused by a changing climate. This poses potential problems for managers in the Northern Glaciated Plains where fishing generates millions of dollars annually for local and state economies, and cool-water fish like Walleye are extremely popular. The Resist-Accept-Direct (RAD) framework is a new tool for responding to environmental changes due to climate change in ecosystems where there are elevated levels of uncertainty and variability. The RAD framework allows managers to determine if it is most advantageous to a) Resist the change by working to maintain the current ecosystem, b) Accept the changing ecosystem, or c) Direct the change to shape the ecosystem into a new one that achieves the manager’s goals. For this tool to be used, relationships between current habitat characteristics and fish communities need to be determined. Potential changes in fish communities can then be assessed using predicted future environmental conditions due to climate change. Our objective was to classify North and South Dakota lake fish assemblages based on environmental conditions using a multivariant regression tree (MRT). To create this MRT, we examined current environmental conditions including surface area, fetch, shoreline development index, water temperature, watershed area, and watershed land use. Future research will incorporate predicted environmental change to examine shifts in fish communities. The results of this study could guide managers in determining a) which lakes may be most at risk for experiencing changing fish communities, b) which RAD strategy could be best suited for each lake, and c) identify which lakes could be prioritized for ecosystem management (e.g., species and location of fish stocking, habitat renovations) to maintain angler satisfaction.

AUTHORS: Levi Suchla, University of Minnesota; Lynn Waterhouse, University of Minnesota/U.S. Geological Survey

ABSTRACT: Mille Lacs Lake is an economically, recreationally, and culturally significant fishery, with Walleye being one of the the main targets for anglers. Over the past 30+ years, numerous biotic and abiotic changes have occurred within the lake and have had an impact on the fishery. This project aims to explore what factors have had the biggest influence on the body condition of walleye, understand the impact of some aquatic invasive species that are present in the lake, and determine the trends and shifts in walleye body condition and growth over time in relation to changing conditions.

AUTHORS: Maddy Siller, South Dakota State University; David Coulter, South Dakota State University; Kaden Ball, South Dakota State University; Mark Kaemink, University of North Dakota; Taufique Mahmood, University of North Dakota; Matthew Maldonado, University of North Dakota; Michaela Neal, University of North Dakota; Ayon Saha, University of North Dakota; Alison Coulter, South Dakota State UNiversity

ABSTRACT: It is known that temperature impacts fish growth and that the influences of temperature on growth depends on the thermal optima of a particular species. This means that the extent of climate change impacts on growth and, ultimately, body length and body weight may vary by species. Additionally, understanding how latitudinal temperature variation influences fish growth may inform planning and management decisions for the future. This is due to climate change potentially producing similar differences to what is already observed with latitudinal variation within species. A common method of assessing fish growth is with well-established bioenergetics equations. However, using bioenergetics equations requires knowledge on food availability. When potential food is unknown, scope for growth (max possible growth at a given temp) can be used to assess potential growth and compare across species, locations, and times. Our goal is to determine how habitat quality for multiple cool and warmwater fishes has changed historically (past 40 years) throughout their distribution. In order to do this, we will (1) quantify how scope for growth and therefore habitat quality has changed in the past 40 years for lakes within species’ ranges, (2) compare how habitat quality has changed across latitude, and (3) compare how habitat quality has changed across species with different thermal optimum temperatures for consumption. Understanding which species have already experienced changes in habitat quality can inform future management under climate change. Additionally, this will reveal what species may be the most resilient to warming temperatures and which may need more support/management.

AUTHORS: Caleb J. Branam, Michigan State University; Holly S. Embke, Midwest Climate Adaptation Science Center, U.S. Geological Survey; Chris L. Cahill, Michigan State University

ABSTRACT: A key challenge in inland fisheries is assessing numerous lakes across vast landscapes within an agency’s jurisdiction given limited resources. To reconcile this, a variety of data-limited methods have been developed to assess the status of inland fish populations. However, these tools often do not explicitly address the potential for population dynamics, or they make strong assumptions that a given population or stock is at equilibrium. Furthermore, these assessment tools are rarely simulation tested in inland fishery settings to determine their efficacy. Without knowing how these methods perform when confronted with simulated dynamics where truth is known, the effectiveness of such tools remains uncertain. Our objective was to evaluate how commonly used assessment methods for Walleye Sander vitreus performed when tested against simulated data. To achieve this, we developed an age-structured simulation model for Walleye and then evaluated the performance of the following commonly used assessment methods: mark-recapture, catch per unit effort as an index of relative abundance, size-structure indices as an index for population status, and production-based dynamics as an index of population status. This presentation will lay out the research plan for our study, present initial results for at least one assessment method, and touch briefly on the implications of potential results.