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Predicted effects of angler harvest on largemouth bass populations in northern Wisconsin lakes

Electrofishing in northern Wisconsin

Duration

January 2012 - December 2014

Narrative

Largemouth bass Micropterus salmoides abundance has increased in many northern Wisconsin lakes over the last decade. Density-dependent effects on largemouth bass growth and size structure and the potential for bass interactions with other popular sport fish such as walleyes Sander vitreus are concerns among anglers and biologists. To reduce largemouth bass abundance, the statewide minimum 15-in total length (TL) limit for bass has been removed from some northern Wisconsin lakes. However, available information suggests that exploitation of largemouth bass is generally low (i.e., < 10%) and it is unclear whether angler harvest will be sufficient to actually affect bass abundance in these lakes. Furthermore, several recent studies suggest that anglers voluntarily release most of the black bass they catch, so liberalization of harvest regulations may not result in substantial increases in bass exploitation. Our objective was to use predictive modeling to determine if largemouth bass abundance, recruitment potential, and size structure in four northern Wisconsin lakes would change in relation to instantaneous fishing mortality rates (F) and changes to harvest regulations. During 2012 and 2013, we collected information on population demographics and dynamics of largemouth bass populations in Big Arbor Vitae, Big Sissabagama, Little John, and Teal lakes in northern Wisconsin. We used this information to formulate population-specific models that were used to simulate the effects of: 1) the current 14-in minimum length limit; 2) a 14-in maximum length limit; 3) no minimum length limit; 4) a 12- to 15-in harvest slot length limit (i.e., fish between 12- and 15-in can be harvested); 5) catch-and-release; 6) an 18-in minimum length limit. No minimum length limit was most effective at reducing abundance by ≥ 25%, although high levels of fishing mortality for Wisconsin anglers (F ≥ 0.2) were necessary to achieve this reduction. A 14-inch maximum length limit or 12-15 inch harvest slot length limit were predicted to provide the most equitable tradeoff between reductions in abundance and size structure, but improvements in RSD-15” ≥ 10% were only observed if F was ≥ 0.10.

Research Products and Activities

Thesis

  • Schnell, K.E. 2014. Predicted effects of angler harvest on largemouth bass populations in northern Wisconsin Lakes. M.S. Thesis. University of Wisconsin-Stevens Point 58 p. Download  | 

Presentations

  • Schnell, K., and D. Isermann. February 2013. Replicating otolith ages for largemouth bass in northern lakes: a comparison of scales and spines. Wisconsin Chapter of the American Fisheries Society Annual Meeting. Rothschild, Wisconsin.
  • Schnell, K., D. Isermann, M. Hansen, and J. Hansen. February 2013. Predicted effects of angler harvest on largemouth bass abundance in northern Wisconsin lakes. Wisconsin Chapter of the American Fisheries Society Annual Meeting. Rothschild, Wisconsin.
 

Current Staff

Federal Staff: 102

Masters Students: 247

Phd Students: 163

Post Docs: 55

University Staff: 266

5 Year Summary

Students graduated: 722

Scientific Publications: 1960

Presentations: 4355

 

Personnel

Funding Agencies

  • Wisconsin Department of Natural Resources

Links

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