Population Dynamics of Lake Whitefish in the Apostle Islands Region of Lake Superior

Seider, Michael; Schram, Stephen

Lake whitefish (Coregonus clupeaformis) is one of the most valuable commercial species throughout the Great Lakes and currently the dominant commercial species in the Apostle Islands region of Lake Superior. Although whitefish are widely considered resilient to commercial exploitation, the sustainability of the current harvest of whitefish is still a management concern. The objective of this report was to consolidate available data to better understand the population characteristics of whitefish in the Apostle Islands region. Commercial and sport harvest and fishery independent surveys indicated whitefish abundance has increased since the 1970s. Since 1999, growth and condition fluctuated but appeared to decline slightly after 2002. Annual mortality rates were relatively low compared to other commercially exploited whitefish populations in Lake Superior. Amphipods were an important prey item throughout the year although whitefish diet changed seasonally. Since amphipod densities have not changed recently a slight decrease in growth and condition is probably due to density dependence as seen in other populations in Lake Superior. Conservative regulation of the whitefish fishery through measures such as commercial gill net effort control, fish refuges, and closed seasons is likely providing biological sustainability in the face of historically high commercial harvest.