Gary Engberg Outdoors

Managing Wisconsin Lakes Spring Netting on Madison’s Lake Mendota 4-30-09

gengberg April 30th, 2009

Every spring as soon as the ice goes out in many of Wisconsin’s lakes, the Wisconsin Department of Natural Resources personnel is out doing fish surveys on many of the state’s lakes. There are two kinds of surveys done, one kind is a Comprehensive Survey and the other is Index Sampling.
In the Comprehensive Survey, the DNR combines intensive spring fyke netting and spring and fall electro fishing runs to cover the entire lake being surveyed. The overall purpose of this survey is to describe the size and condition of the major fish populations of recreational interest, assess regulations, and suggest necessary managerial actions. The Comprehensive Surveys target walleye, northern pike, and muskie while providing some insight into the adult components of those fisheries. These surveys are also used to make population estimates.
Index Sampling uses only electro-fishing which is directed at selected sites in both the spring and fall. Bass, panfish, and young of the year fish are most effectively monitored by Index Sampling.
This spring, I was lucky enough to be able to accompany the DNR netting crews on Madison’s Lake Mendota. This year, the early spring fyke netting began in the middle of March and continued into the third week of April. Weather is a major component in the spring netting with cold temperatures and strong winds affecting the ability of the DNR workers set nets properly and catch fish. I saw nets that had over 300 channel catfish over 10 pounds in them one day and the next day had zero fish. Even in the spring, fish are constantly moving and seeking out warmer water and areas for spawning. Kurt Welke, DNR Fisheries manager for Dane County, Scott Harpold, a DNR Fisheries Technician Manager, and Dick Brandt, a part-time DNR Fisheries worker did the vast majority of the research and work on Lake Mendota in rain, snow, cold, and the strong winds of a Wisconsin spring.
The spring survey begins when the crews stretch the long fyke nets perpendicular to the shore where adult walleye, muskie, northern pike, and other gamefish congregate in spawning areas. The nets are checked regularly from everyday to every other day including Saturdays. When the nets are checked and hold fish, the crew measures the fish, determine their sex by the presence of eggs or milt, mark the fish by fin-clipping or tagging, and in some cases removing a scale or a dorsal fin spine sample for later analysis before releasing the fish. All of this data is carefully recorded for later study, analysis, and research. I witnessed a number of fish from the nets that were recaptures meaning that they had been caught in a net in previous years and fin-clipped.
The Madison Chain of Lakes include; Lake Mendota, Lake Monona, Lake Wabesa, Lake Wingra, and Lake Kegonsa. The fish netting and sampling follow a 5 year rotation on these lakes. Every year, one of the 5 lakes receives a Comprehensive Survey while the other lakes receive a spring and fall Index Sample. This was Lake Mendota’s year for a Comprehensive Survey.
As a stocked fishery with little if any natural reproduction, Lake Mendota’s walleye and pike numbers are better than most of the lakes in Wisconsin. The size structure is excellent and harvest or legal-size walleyes are well represented. There also is a growing and significant smallmouth population and a quality largemouth fishery. The perch numbers are down over the long-term mean, but the hatches of 2004 and 2005 should be of good size. Continue Reading »