DNR Spring Walleye Survey

Shocking Lipsett Lake 

(Click on this picture to get a larger version)

 

 

This is the first time anyone remembers the DNR shocking the lake during the daytime hours.

(picture submitted by Aaron and Holly Tempel)

 

 

One of the things that people who don't live on Wisconsin Lakes seldom see is the DNR shocking the lakes.  Here is a picture from our dock of the shocking -- and below is an explanation of how and why they do it.  Nets were put in Friday -- they shocked the lake tonight, which is Monday.

Just thought you might be interested.

Spring Adult and Total Population Estimates

One important method the Wisconsin DNR uses to assess walleye populations is spring adult and total population estimates. Walleyes are captured with fyke nets each spring shortly after ice out. Each fish is then measured (total length to the nearest tenth of an inch) and receives a permanent mark such as a fin clip. All sexable fish and those of unknown sex that are at least 15 inches in length are considered to be part of the adult population and are given a specific mark unique to that lake. Fish of unknown sex that are less than 15 inches in length are considered juveniles and given a different lake-specific fin clip. The goal is to mark at least 10% of the total spawning population, and marking continues until this target is reached or spawned out females begin to appear in the fyke nets.

To estimate adult abundance in each lake,  walleyes are recaptured 1-2 days after netting with the use of electrofishing equipment. The entire shoreline of each lake, including islands, is electrofished, and this effort is used to calculate an adult walleye population estimate. All walleyes in this recapture run are measured and examined for marks. In addition, all unmarked walleyes are given an appropriate mark so that a total  population estimate can be calculated. This is done via a second electrofishing effort approximately two weeks later using methods similar to those used to obtain adult population estimates.

Population estimates are calculated by multiplying the number of marked fish known to be in the lake by the total number of fish captured, then dividing
by the number of marked fish captured. The abundance of walleyes in each of four length classes (<11 .9="" 12-14.9="" 15-19.9="" and="">20") is estimated, and these are summed to estimate the adult and total abundance of walleyes in each lake. If spearing occurs after the start of the marking period, the number of marked walleyes speared is subtracted from the number of marked fish at large during the recapture period. These fish are then added back to the estimated number of fish present at the time of marking for the appropriate population (adult or total).

Fish populations in general, and walleye populations in particular, are extremely variable and can change drastically from year to year, so a
continuing survey of lakes provides critical information on trends occurring in these populations. However, it is logistically impossible to obtain accurate population estimates from all harvested lakes in the Ceded Territory each year. Therefore, random subsamples of lakes are selected each year for walleye population estimates.