Assessing Walleye Population Recovery in the Changing Environment of Northern Lake Michigan

Extensive efforts to rehabilitate remnant walleye populations in Little Bay de Noc, Lake Michigan have been ongoing since 1969, when populations nearly collapsed.  Though some natural reproduction was documented as early as 1988, no quantitative data occurred for assessing the contributions of hatchery- and naturally-produced fish.  We initiated an oxytetracycline marking study to fill this gap, and documented considerable natural reproduction of walleyes.  Over time, the bay was further altered by increased temperatures and invasive dreissenid mussels, leading to shifts in water clarity, prey fish abundance, walleye behavior and distribution, and ultimately, the walleye fishery.  Such changes complicated efforts to assess the potential of the bay for walleyes, the extent of population recovery, and guide future walleye stocking.  The overall fishery management goal is to achieve a stable (preferably self-sustaining) walleye population in balance with the prey fish community.  We engaged constituents to develop a decision-support tool for guiding future stocking decisions (i.e., facilitate movement towards our goal).  The tool incorporates data from ongoing surveys of forage fish and walleye abundance, growth, and reproduction.  The risk-averse approach of the tool will hopefully guide the walleye population toward our management goal despite the uncertain future condition of the bay.