Management of lake sturgeon on the Winnebago System - long term impacts of harvest and regulations on population structure

The Winnebago System, Wisconsin, supports one of the largest self sustaining stocks of lake sturgeon, Acipenser fulvescens , in North America. Winter spearing harvest of the Winnebago sturgeon population has been actively regulated since 1903 and actively assessed since the 1940's. While historic population assessments have shown a steady increase in sturgeon densities in the system, recent surveys indicated overexploitation of adult females. From 1991–97, 13714 sturgeon were assessed through harvest and spawning surveys to characterize the status of the current population, and historical data from DNR files were reassembled and analyzed to discern population trends over the last 40 years. A summary of management actions since 1903 was completed and reviewed in the context of long term population trends. 1991–97 annual harvests averaged 1337 sturgeon with adult females comprising 46% of the annual harvests from 1991–96 and 34% of the harvest in 1997 following a reduction in the minimum size limit. With the higher size limit, estimated annual exploitation of adult females was 2 to 3 times higher than that of adult males. Historic harvest and population trends showed the benefits of conservative bag limits and harvest season lengths combined with strict law enforcement, and habitat protection, which resulted in an estimated 58% reduction in the annual harvest between 1955 and 1965 and a four fold increase in legal stock densities from 1955 to 1990. The analyses of the historic data reinforced the necessity of standardized long term harvest and population assessments for effective management of sturgeon populations and fisheries. Public involvement is also identified as an integral component to effective sturgeon management.