2020 Lake Winnebago Bottom Trawling Assessment Report

ADAM NICKEL DNR Winnebago System Gamefish Biologist April 2021

The Lake Winnebago bottom trawling assessment is critical for monitoring the Winnebago System fish community, and area anglers are eager to learn the results each year. The trawl assessment has been conducted annually since 1986.

The main objectives include providing critical information on year-class strength of game and nongame fish species, monitoring trends in the forage base, and monitoring general population trends of game and nongame fish species. One of the annual trawl survey staples has been the dedicated volunteer base that helps complete the survey each year.

However, 2020 was a different year, and we were unable to use volunteers due to work restrictions associated with the COVID-19 pandemic. The DNR developed a protocol for completing the 2020 survey that included using limited DNR staff to complete the survey while wearing masks and practicing social distancing at all times. This protocol laid the framework for the 2020 trawl survey to be conducted safely. The annual survey consists of sampling 46 standardized GPS waypoints during the first week of August, September and October. Each sample involves towing a 27’ wide trawl along the bottom for five minutes at 4 miles per hour, equating to around 1-acre of area sampled. Staff captured a fair amount of adult fish during the survey, but the trawl is most effective at catching small fish (young of year (YOY) and yearlings).

The standardized survey has been conducted annually since 1986, thus providing a long-term data set to evaluate trends in recruitment and adult abundance of various important game and nongame fish species on the Winnebago System.

The 2020 trawling results revealed several highlights, including record catch rates of YOY freshwater drum and yellow perch, a strong crappie hatch and a measurable walleye year class. Overall, there were 15 species of YOY fish sampled for a total of 79,835 YOY fish caught during the 2020 trawling survey. It was noteworthy that 2020 had the highest catch rate for YOY bluegill (1.3/trawl) on record (Appendix 1). For adult fish, there were 18 different species sampled for a total of 42,480 adult fish captured (Appendix 2). Interestingly, 2020 also had the highest number of adult lake sturgeon sampled on record (43 fish).