Wisconsin Opens Unlimited Goby Harvest

The round goby's journey to Wisconsin began in 1990, when the species was first discovered in the St. Clair River, believed to have been introduced from the Black and Caspian Seas via the ballast water of ocean-going ships. By 1994, this aggressive, bottom-dwelling fish had rapidly spread to all five Great Lakes. Before their confirmed arrival in Lake Winnebago in June 2025, gobies were detected in Little Lake Butte des Morts in August 2015. This discovery prompted the immediate closure of the Menasha Lock by the Fox River Navigational System Authority in an effort to halt their upstream progression into the larger Winnebago system. The ecological threat posed by round gobies is multifaceted. They are voracious predators of the eggs and young of native sport fish, including walleye and smallmouth bass. Their aggressive nature allows them to outcompete native bottom-dwellers like sculpins and darters for food and prime habitat, and they can reproduce up to six times in a single summer. The economic consequences of goby invasion have been documented elsewhere. In Ohio, for example, the state closed the popular smallmouth bass fishery on Lake Erie during May and June because unguarded nests were being decimated by gobies; one study observed gobies eating up to 4,000 bass eggs in just 15 minutes. Round gobies also pose a threat by altering the food web. They consume large quantities of another invasive species, zebra and quagga mussels, which can lead to the bioaccumulation of toxins. These toxins can then be passed up the food chain to birds and larger fish, and have been linked to outbreaks of avian botulism. While some larger sport fish like bass and walleye do prey on adult gobies, the overall impact of the invasion is a net negative for the ecosystem. The DNR's move to an unlimited harvest is an attempt to mitigate the spread and control the population of an invasive species that has proven nearly impossible to eradicate once established.