Midwest Fish & Wildlife Conference 2018

AUTHORS. Christopher J. Sullivan, University of Wisconsin-Stevens Point; Kaitlin Schnell, University of Wisconsin-Stevens Point, Current address: Army Corps of Engineers, Seattle District; Jonathan Hansen, Wisconsin Department of Natural Resources, Current address: Minnesota Department of Natural Resources; Daniel A. Isermann, U.S. Geological Survey, University of Wisconsin-Stevens Point

ABSTRACT. Environmental variation can lead to shifts in fish communities that require changes in management strategies.  Largemouth bass Micropterus salmoides abundance has increased in many north temperate lakes, prompting concerns regarding potential inter-specific interactions, declines in bass size structure, and potential changes to harvest regulations.  However, current exploitation rates are too low to effectively reduce abundance.  Therefore, age-structured models were used to predict population responses to increased fishing mortality (F) under six different harvest regulations for eight Wisconsin bass populations representing a range of densities.  Regardless of harvest regulation, changesin abundance and size structure were unlikely to occur if rates of F are = 0.10.  No minimum total length (TL) limit had the greatest potential for reducing abundance and spawning potential ratios by = 25%, but relatively high levels of F (= 0.20) were required.  A 356-mm maximum TL and a 305-381 mm TL harvest slot limit provided the most equitable trade-offs between reducing abundance and maintaining size structure.  If reducing bass abundance is a management objective, targeted removal of bass or angler education programs promoting harvest may be necessary.