Management & Regulation Research: Walleye Stock Differentiation and Recruitment in the Lake Winnebago System

Objectives of this research project are to test the hypothesis that the three spawning sub-populations of walleye inhabiting the Lake Winnebago system and are discrete, reproductively isolated stocks. The three sub-populations are Wolf River marsh spawners, Fox River marsh spawners, and Lake Winnebago reef spawners. If stocks are isolated, the relative contributions of each stock to Lake Winnebago will be assessed.

Background

Lake Winnebago is the largest walleye fishery in Wisconsin and annually supports a large and valuable recreational fishery. The walleye populations have been extensively studied over the years with emphasis on impacts of freshwater drum removal and understanding walleye spawning activity. It has been hypothesized that there are three different spawning stocks: two stocks that migrate up the Wolf and Fox Rivers to spawn, and a third stock that spawns on rocky substrate in Lake Winnebago itself.

If these stocks are ecologically or genetically distinct, it would be necessary to manage each separately. For example, protection of fragile upstream spawning areas and monitoring of angler harvest of the upstream migrating fish would be a priority for the river-spawning stocks, while lake water levels might be more important for the lake-spawning fish. Also, the ability to monitor the relative contribution of each spawning population to the overall lake recruitment would permit evaluating management activities. Determining whether these stocks are distinct can be done through tagging studies, genetic analyses, or comparing morphometric characteristics (i.e., physical measurements).

Differentiating spawning stocks will allow evaluation of the cost effectiveness of current management activities. Future management actions such as habitat protection or spring harvest regulations can respond to differences in the reproductive success of each stock. If spawning stocks are not separate, unnecessary stock-specific management activities can be avoided.