Research Explores Conservation Strategies for Shifting Walleye Populations
Given the challenges that warming waters pose to walleye populations, USGS researchers created a data-rich “RAD Walleye Tool” that can help managers determine which lakes are the best candidates for different conservation strategies now and in the future.
At the heart of Wisconsin’s rich fishing culture is the walleye – a legendary fish with big, pearly, reflective eyes. In Ojibwe, the fish is called “ogaa" and symbolizes knowledge, illumination, and guidance. Their unique eyes guide them through cool, dark, murky waters, making them formidable predators and a challenging catch for anglers.
Warming waters have made many lakes that were once walleye strongholds struggle to keep populations. In response to these climate challenges, USGS-supported researchers created the “RAD Walleye Tool” to help managers evaluate if lakes will be able to sustain walleye populations in the future.
In this context, “RAD” isn’t slang for “cool” or “awesome,” but is an acronym for the "Resist-Accept-Direct" conservation framework that guides it. The framework helps managers prioritize lakes for conservation with three options: resisting change, accepting change, or directing the system towards a new desired state. The formula considers the size and age structure of walleye populations and the current and future habitat conditions of each lake.
Dr. Colin Dassow developed the web app while he was a post-doc working at the USGS Missouri Cooperative Fish and Wildlife Research Unit (CRU) on a project funded by the USGS National Climate Adaptation Science Center (National CASC). He used data and insight from partners like the Wisconsin Department of Natural Resources (WDNR), where he is now a research scientist, and the Great Lakes Indian Fish and Wildlife Commission (GLIFWC).
Dassow suggests the best way to start using the tool is to search for a “lake of interest.” His is Augustine Lake in Ashland County, a lake where he learned to fish while visiting his grandfather growing up. He still fishes in Wisconsin at least once a week but knows that all the lakes he visits may not yield the same species in the future.
With colleagues, including National CASC biologist Dr. Abigail Lynch, Dassow published a study that categorized 6,594 Wisconsin lakes in the RAD framework. Given expected climate change, they predicted that 653 lakes would still be able to maintain self-sustaining walleye populations and suitable lake conditions for walleye by the year 2100. In these lakes, managers may be able to resist walleye loss by stocking fish, enacting catch restrictions, or protecting and improving habitat.
Resisting change is a status quo conservation approach, but there are alternatives that sometimes may be more sustainable or realistic. For instance, it may become impractical to stock lakes that will no longer have hospitable conditions for adult walleye.
“It’s not a matter of effort, it’s a matter of what the environment can sustain,” explains Dassow. “Some lakes might never return to their former walleye glory due to climate realities.”
Managers could consider directing the ecosystem towards a new state, like preserving other species to create alternative angling or tribal harvest opportunities. In many fisheries, largemouth and smallmouth bass can be alternatives to walleye due to their adaptability to warming waters. Managers could also consider accepting the lake’s current trajectory, especially if management actions aren’t feasible or are unlikely to be effective.
Even for those outside of the management community, Lynch recommends exploring the web app. It can be “a kind of thought exercise” to go through the process as managers might. But she emphasizes that social, cultural, and economic perspectives complicate this “scientific” way of categorizing lakes. Shifting walleye populations will have consequences on outdoor tourism, local businesses, and traditional harvest practices of Tribal Nations.
“There’s an emotional tie to these systems that’s important to recognize in addition to the ecological consequences of climate change,” says Lynch.
A fishing guide told Dassow that he’s been witnessing more clients transition from catching walleye to eat to catch-and-release practices – reflecting an encouraging trend among anglers who are embracing conservation ethics.
“It’s not just about catching and eating fish,” Dassow says, “It’s about the experience, the joy of the catch, and preserving our fish populations for future generations.”
Looking ahead, he hopes to incorporate spatial considerations into the app’s formula, like driving distances, to ensure that walleye fishing remains accessible to as many people as possible across the state. Dassow says, “I see [the app] as a living thing that we’ll always be working on.”
As the lake systems continue to change, the team will continue to adapt the app to help ensure sustainability of these important resources now and into the future.
The ONB features articles from Cooperative Fish and Wildlife Research Units, U.S. Geological Survey. The Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about.
Author: Shannon Bayliss, Oak Ridge Science and Education (ORISE) Research Fellow, National Climate Adaptation Science Center
Edits by: Jordan Bush, USGS National Climate Adaptation Science Center; Abigail Lynch, USGS Ecosystems Mission Area, Kate Malpeli, USGS Ecosystems Mission Area; and Colin Dassow, Wisconsin Department of Natural Resources
Author: Shannon Bayliss; Photo Credit: Dan Isserman, USGS; November 15, 2023
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