Inland fishes which are non-migratory are managed at the state level; federal agencies are involved in the management of migratory fishes, commercial fisheries and endangered species. Walleye are considered a non-migratory inland fisheries, and in Wisconsin during the 1980's were managed by the Wisconsin Department of Natural Resources. (This responsibility is now shared by many Tribal agencies.)
In North America fisheries are divided into "cold water" (Salmon, Greyling, Trout), "cool water" (Walleye, Muskellunge, Smallmouth Bass), and "warm water" (Largemouth Bass, Channel Catfish). The lake and river fisheries in Wisconsin are cool water fisheries while in Kansas we have a warm water fishery.
Throughout much of the 20th century it was common practice for state fisheries managers to poison entire lakes and restock them with selected species of gamefish and a limited number of prey species to support them. This happened throughout northern Wisconsin, and is one of the reasons why many lakes have only one or two species of predatory fish and a small number of prey (for example, Walleye as the predator and Yellow Perch as the prey).
There has been an increasing trend in recent years to take other values into consideration when managing inland fisheries, for example conservation of endangered species, biodiversity, maintaining the integrity of genetic stocks and ecosystem functioning. As a result there is a greater tendency to use information from ecology and community ecology to manage in a more "natural" fashion and less reliance on total control of the lake ecosystem.
There has also been an increasing recognition that population models are based on unrealistic assumptions; not all individuals are the same, "maximizing" exploitation rates may leave too little room for error, the environment changes over time so there is no stable carrying capacity, and so on. As a result fisheries managers are developing more rigorous techniques to measure population levels, they are taking into account population structure (size, age, genetic), developing more sophisticated models, and importantly, backing off from the idea of maximizing harvest. For example, in Wisconsin it is now more common to set the take level at 35% of MSY (leaving 65% of the estimated population) rather than 50% (leaving 50% of the estimated population). It is also common to set slot limits for the size of the fish caught in order to protect young fish and the large, highly fecund females. (A slot limit might specify that you can only take fish between 8-12" for example.)
In the next sections we will discuss some of the scientific background that informed fisheries management during the time period covered in "Walleye Wars" in order to understand some of the disagreements and misinformation involved in the conflict.
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