Modeled Walleye regulation outcomes in a Midwestern reservoir with varying forage and Walleye density

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Krogman, Rebecca M.
Dodd, Benjamin J.
Otting, Andy
Weber, Robert E.
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© 2021 American Fisheries Society
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Natural Resource Ecology and Management
In a put-grow-take fishery, Walleye Sander vitreus management may require length-based regulation and depends on population dynamics such as growth, which in turn depends on forage. Big Creek Lake, an important Iowa Walleye fishery, underwent forage changes twice within two decades. Concurrently, Walleye density changed due to increased stocking and reduced emigration, resulting in four scenarios: A) low-density Walleye with Gizzard Shad forage, B) low-density Walleye with centrarchid/percid forage, C) high-density Walleye with centrarchid/percid forage, and D) high-density Walleye with Gizzard Shad forage. We examined Walleye population dynamics and relative effects of four length-based regulations during each period using sampling data from 1998-2000, 2006-2008, 2013-2015, and 2019. Walleye in Big Creek Lake likely experienced density-dependence when Walleye density was high and Gizzard Shad were absent, resulting in depressed growth, low condition, increased natural mortality, reduced exploitation, and ineffectiveness of regulations. At lower Walleye densities, the centrarchid/percid forage supported Walleye growth and condition equivalent to when Gizzard Shad were present. Fishing regulations for enhancing Walleye size distribution or yield differed over time due to shifting population dynamics and angler exploitation, and were notably ineffective during Period C. The preferred regulation for the current scenario (high-density Walleye with Gizzard Shad) depends on angler preferences for higher catch or larger fish. Big Creek Lake’s Walleye fishery provided a useful demonstration of how rapidly a population can respond to changes in density and forage, and therefore how dynamic fishery management needed to be.
This is the peer reviewed version of the following article: Krogman, Rebecca M., Benjamin J. Dodd, Andy Otting, Michael J. Weber, and Robert E. Weber. "Modeled Walleye regulation outcomes in a Midwestern reservoir with varying forage and Walleye density." North American Journal of Fisheries Management (2021), which has been published in final form at doi:10.1002/nafm.10718. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.