AUTHORS: Greg G. Sass, Wisconsin Department of Natural Resources; Colin Dassow, Wisconsin Department of Natural Resources; Holly Embke, United States Geological Survey; Zachary Feiner, Wisconsin Department of Natural Resources and University of Wisconsin-Madison; Joseph Mrnak, Wisconsin Department of Natural Resources; Stephanie Shaw, Wisconsin Department of Natural Resources
ABSTRACT: Many walleye populations in the Midwestern United States have declined due to inconsistent or failed natural recruitment, with stocking often failing to rehabilitate natural recruitment or sustain quality fisheries for tribal subsistence and angler harvest opportunity. Numerous factors have been implicated in walleye natural recruitment declines including climate change and phenological variability, habitat loss, production overharvest, invasive species, fish community compositional change, and fisher behavior. Walleye populations have also been shown to be prone to depensation. Still, some walleye populations have remained resilient to these disturbances offering hope for continued natural recruitment and population persistence. We discuss several alternative management strategies to maintain walleye population resilience by focusing on the probability of depensation in a walleye population (rather than assuming compensation) and assessment of yield:production ratios. Critical depensation is a positive adult biomass or abundance threshold below which a population collapses. Because the probability of depensation for Wisconsin walleye populations is unrelated to population productivity, resilience to depensation is critically dependent on maintaining sufficient adult densities to avoid crossing this ecological tipping point. Resilience can also be maintained by estimating walleye population adaptive capacity to harvest and ensuring that yield does not exceed annual production. Both strategies suggest an immediate need to reduce exploitation rates and create cultivating conditions for walleye to ensure the greatest probability of not crossing a depensatory threshold. Further, walleye “bright spots” (i.e., populations showing evidence for the greatest resiliency now and in the future) should be managed most conservatively as they are likely to draw the most fisher effort to remaining harvest opportunities. Recognizing walleye fisheries as social-ecological systems, ecosystem-based fisheries management approaches, and challenging traditional fisheries management paradigms will be paramount to ensure the sustainability of walleye populations.
AUTHORS: Melissa Wuellner, University of Nebraska at Kearney; Keith Koupal, Nebraska Game and Parks Commission
ABSTRACT: The recruitment of Walleye (Sander vitreus) has become less reliable through time as these populations face high angler exploitation and changing climatic conditions. While the native range of Walleye does extend to the Gulf of Mexico, the populations in Nebraska represent the southern and western edges of traditional natural recruiting populations. As such the challenges these populations face potentially represent the challenges the populations in more traditional northern climates may face as climatic conditions become more variable. In Nebraska, Walleye management in many reservoirs would fall under the “Resist-Accept” continuum as the sustainability of these populations relies largely on stocking. The Resist-Accept-Direct (RAD) framework has been used to frame Walleye management decisions, but the question remains as to whether the RAD framework applies to populations where summer ambient temperatures may be much warmer than locations where related research has been published. In this presentation, we will present case studies that illustrate the history of stocking over more than 40 years, whether stocking helps to meet reservoir-specific management goals, and what the future of the Walleye stocking program may be. Context for the advantages and disadvantages of the variable approaches to maintain Walleye populations along with potential consequences will be discussed.
AUTHORS: 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; Jason Breeggemann, Wisconsin Department of Natural Resources; Troy Zorn, Michigan Department of Natural Resources
ABSTRACT: Green Bay supports one of the most prominent recreational walleye fisheries in North America. The recreational fishery provides annual harvests that exceed 100,000 fish and millions of dollars to local economies. Additionally, walleye in Michigan waters contribute to an important tribal subsistence fishery designated by the Great Lakes Consent Decree for the 1836 Treaty of Washington. The popularity and socioeconomic importance of this fishery makes walleye a species of primary management interest for the Wisconsin and Michigan Departments of Natural Resources, who jointly manage this important resource. The current status of the Green Bay walleye fishery represents the successful culmination of several recovery efforts. Following collapse of walleye stocks in the 1960s due to habitat destruction, pollution, overexploitation, and invasive species, walleyes were intensively stocked by the Wisconsin and Michigan Departments of Natural Resources. Stocking in Wisconsin waters was largely discontinued in the mid-1980s and the stock is now entirely supported by natural recruitment. Conversely, the stock in Michigan waters in the northern portion of the bay has not fully recovered despite continued stocking. We will provide perspectives on how factors including productivity, dreissenid mussels, prey diversity, thermal-optical habitat, and portfolios of potential recruitment sources may contribute to the overall resilience of walleye stocks in Green Bay and the potential disparity in resilience between stocks in the northern and southern portions of the bay. We will also discuss various management and research activities that have helped maintain, and can potentially help build, resilience of walleye populations in Green Bay and elsewhere.
AUTHORS: David G. Fielder, Michigan Department of Natural Resources, Alpena Fisheries Research Station
ABSTRACT: The Walleye population of Saginaw Bay was historically among the largest in the Great Lakes. The early commercial fishery averaged a yield of nearly 480 metric tons annually from the 1880s to the middle of the Twentieth Century. The population collapsed, however, due to water quality declines, sedimentation of off-shore reef spawning habitat, the construction of dams that impeded spawning migrations, and the effects of invasive species. The population endured declining conditions for some decades but finally succumbed in the mid-1940s after successive year class failures. The commercial fishery was formally closed in 1970. The basis for recovery began with the passage of clean water legislation in the early 1970s. A fingerling stocking program was established by the early 1980s and a recreational fishery emerged soon after. A recovery plan was developed by the Michigan DNR in the 1990s and called for creating a predation barrier to the invasive Alewife which by then had been implicated as a major impediment to reproductive success of Percids. The strategy was to increase stocking to more than 2 million spring fingerlings per year. Other strategies called for improvements to spawning habitat including the restoration of off-shore reefs and dam removal. A profound food web shift unexpectedly took place in 2003 which resulted in the sudden collapse of the lake wide Alewife population. Released from this deleterious impediment, reproductive success of Walleye in Saginaw Bay exploded. Stocking was discontinued in 2006. Recreational harvest rate increased 555% and harvest by 311% since 2005 compared to pre-recovery averages. The Walleye population continues to expand and today is believed to number more than 12 million age-2 and older. The rapid recovery of Walleye in Saginaw Bay illustrates the remarkable resiliency of the species. When obstacles to reproduction are removed, the species can respond quicky.
AUTHORS: Travis Hartman, Ohio DNR-Division of Wildlife
ABSTRACT: Lake Erie’s walleye population has a long history of resiliency while providing sustainable harvest for sport and commercial fisheries. Walleye have endured system-wide habitat alterations, impactful contaminants, invasive species, and greatly improved fisheries efficiency over the past 125 years. Management agencies acknowledged the need for lake-wide collaboration and began quota management in the 1970s through the Great Lakes Fishery Commission’s facilitation of the Lake Erie Committee. During 50 years of quota management the process has evolved to include a published management plan that was informed by stakeholder input and utilizes long-term datasets to annually run a population model that is paired with harvest control rules which allows the Lake Erie Committee to deliberate and set safe harvest levels. As one of the five Lake Erie Committee agencies Ohio provides technical representation on the Walleye Task Group, provides both fishery data and fishery-independent survey data for the modeling process, and sets fisheries regulations that are responsive to annual safe harvest levels. Lake Erie has been widely recognized as the “Walleye Capital of the World” and Ohio’s sport fishery has harvested from 2.0 to 2.6 million walleye annually since 2019. While management challenges and environmental variability have been a constant even during the recent increases in walleye abundance, the long-term outlook for Lake Erie walleye is exceptional.
ABSTRACT: Each year, the Iowa Department of Natural Resources (DNR) invests significant resources to support its walleye fishery. Determining the success of stocking activities is imperative, but collection of broodstock for hatchery production dominates the appropriate timeframe for sampling and population monitoring, thus only a handful of the stocked waterbodies are ever surveyed. Creel surveys are conducted at a limited number of fisheries. From 2022 to 2024, Iowa DNR partnered with MyCatch, an app-based tournament platform, to conduct a state wide catch-photo-release fishing tournament to determine if angler reported data could provide a reasonable overview of walleye catch rates and length distributions for waterbodies across the state. Sampling survey data were used as a benchmark to evaluate similarity to angler derived data, and initial comparisons were promising but limited. Results from 2022-2024 will be addressed. Scientifically, if angler reported catches are consistent with the standardize sampling and/or creel surveys, it could provide a new, cost-effective way to develop a state-wide assessment of the walleye populations. Identifying locations where stocking success/failure occur, and resilient populations persist, will allow more effective allocations of limited hatchery resources.
AUTHORS: Jeremiah Haas, Constellation Dr. David Bergerhouse, Southern Illinois University Carbondale
ABSTRACT: The Quad Cities Nuclear Station has monitored fish populations in Pool 14 as part of its environmental impact monitoring program for electricity generation since 1971. In 1984, the Station established a fish hatchery onsite with operational support from Southern Illinois University. Walleye is a significant species produced at the hatchery. The Station began stocking walleye in Pool 14 in 1985, and later would include Pool 13 at a lower level, all with the goal of observing population increases from low level stocking in such a large system. This presentation will review the Walleye population changes during that period, using the long-term monitoring data and spring hatchery brood stock data. Fishing regulation changes during that time, which could also have impacted the population dynamics of Walleye populations, will be reviewed as well.
AUTHORS: Nick Schlesser, Minnesota Department of Natural Resources
ABSTRACT: The Minnesota Department of Natural Resources (MN DNR) provides intensive monitoring for the ten largest Walleye (Sander vitreus) lakes in Minnesota through the Large Lake Program. Lake Pepin, located in Pool 4 of the Mississippi River, is the southern most body of water in Minnesota’s Large Lake Program. With a 60-year history of annual sampling the Walleye population from Lake Pepin has been monitored through exposure to numerous stressors but remains one of the most productive fisheries in Minnesota. How some of these stressors have impacted the population and what aspects of the population make it resilient to change will be discussed.
AUTHORS: Todd Caspers, North Dakota Game and Fish Department
ABSTRACT: Devils Lake is one of North Dakota’s most important fisheries. Devils Lake is the state’s 3rd largest waterbody overall and is the largest natural lake in the state. Walleye have long been and continue to be one of the most abundant and sought-after gamefish species in the lake. Walleye were not native to the lake, but were stocked in 1970, and stockings have occurred most years since then. Beginning in 1993, a prolonged period of wetter climatic conditions caused Devils Lake to grow greatly in size and depth. The influx of water also caused the salinity of the lake to decline, which improved walleye spawning success. After 32 years of data collection on Devils Lake, changes in the walleye population have become evident. Over the years, recruitment has increased. The walleye population has also increased in density over time. Smaller walleye in particular have increased in density. However, the increasing walleye densities have led to changes such as lower walleye body condition and reduced growth rates. Lower walleye body condition and reduced growth rates have also occurred in spite of increasing angling pressure and walleye harvests. Potential factors that contribute to the resiliency of the walleye population of Devils Lake include a relatively simple fish community, consistent recruitment, supplemental stocking, adequate growth rates and relatively low mortality rates.
AUTHORS: Laurel H. Sacco, Jeremy L. Kientz1 Gene F. Galinat1, Bill Miller, Jacob L. Davis1 and Steven R. Chipps2
Department of Natural Resource Management South Dakota State University Brookings, SD, 57007
1South Dakota Department of Game, Fish and Parks TOC West-4310 Adventure Trail Rapid City, SD, 57702
2U.S. Geological Survey, South Dakota Cooperative Fish and Wildlife Unit, Department of Natural Resource Management, South Dakota State University, Brookings, SD, 57007
ABSTRACT: Understanding population recruitment is an important step in developing effective Walleye management strategies. In western South Dakota, Angostura, Belle Fourche, and Shadehill reservoirs provide important irrigation needs and flood control. These reservoirs also represent popular destinations for Walleye anglers, although the recruitment dynamics of these fisheries are poorly understood. In Angostura Reservoir, the stocking of larger, fingerling fish successfully augmented year class strength and was the principal driver of Walleye recruitment. In reservoirs where stocking was absent or inconsistent, Walleye recruitment dynamics were influenced by abiotic factors, particularly temperature and hydrologic conditions. Spring temperatures were universally influential in recruitment outcomes, although environmental conditions in late summer and fall were also important. Because recruitment bottlenecks generally occur during early life stages for Walleye, warming rate and(or) elevated temperatures, particularly during spring, may have negative impacts on cohort survival in western irrigation reservoirs.
AUTHORS: Christopher I. Rounds, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota; Holly S. Embke, USGS, Midwest Climate Adaptation Science Center; Zachary S. Feiner, Office of Applied Science, Wisconsin Department of Natural Resources; Quinnlan Smith, Center for Limnology, University of Wisconsin-Madison; Olaf P. Jensen, Center for Limnology, University of Wisconsin-Madison; Jake Vander Zanden, Center for Limnology, University of Wisconsin-Madison; Daniel Isermann, USGS, Wisconsin Cooperative Fishery Research Unit University of Wisconsin–Stevens Point; Gretchen J.A. Hansen, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota
ABSTRACT: Many fields rely on the identification and understanding of “bright spots” (i.e., populations that are performing better than predicted based on environmental conditions) to determine successful management approaches and to replicate success elsewhere. Walleye, a culturally and ecologically important cool water species, has declined in many locations where it once thrived, while at the same time other walleye populations have thrived under similar environmental conditions. These heterogeneous responses have raised questions regarding the role of the environment versus management in shaping walleye populations and how to best manage for resilient populations under changing conditions. Here, we discuss a conceptual “bright spot” framework and differentiate it from a related, but different concept of “hot spots” (i.e., populations that are predictably performing better than average for a given metric). We apply a bright spot analysis to lakes in Minnesota to understand where and why certain walleye populations are performing better than expected. We describe walleye “hot spots” and “bright spots” for walleye recruitment to age-0 and adult relative abundance and highlight actionable factors that are associated with “bright spots”. We welcome discussion on our approach and the relevant metrics of success as a part of this presentation.
