Monday, February 6th, 2023
Monday, February 6th, 2023

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Lake Winnebago, Fond du Lac/Winnebago/Calumet counties

Winnebago’s 2021 fall trawling dredges up good news

By WON Staff

The DNR’s Lake Winnebago fisheries team has been conducting a bottom trawling survey every year since 1986 to establish and follow trends in the big lake’s fish community. The survey allows the team to compare year-class strength and adult abundance of game fish and forage species across 35 years of sampling.

The DNR team doesn’t do the trawling survey alone – each year volunteers donate more than 400 hours of labor to the project that samples 46 GPS waypoints during the first week of August, September and October. Each run involves towing a 27-foot wide trawl along the bottom for five minutes at 4 mph that covers about one acre. The trawl mostly catches young-of-the-year (YOY) and yearlings, but adult fish are also caught.

The team is currently working on the 2022 survey, but results of the 2021 survey are now available. A total of 96,997 YOY fish were sampled in 2021, making it the third-highest YOY count on record. In addition, 57,883 adult fish were captured, representing 23 species. The 2021 trawl survey highlights include above-average walleye and yellow perch year classes, the highest YOY sauger catch rate since 2010 and strong adult catches for yellow perch and bluegills. In addition, strong forage fish catch rates were found, including a record- setting YOY trout perch catch rate, strong adult emerald shiner catch and a measurable YOY freshwater drum year class.

The 2021 YOY walleye catch was 8.2 per trawl, well above the average of 4.6 per trawl.

“The above-average hatch was unexpected based on the lower overall spring water level on the Wolf River,” said Adam Nickel, DNR senior fisheries biologist. “Adequate spring water levels are crucial for providing suitable walleye spawning conditions by allowing adult fish access to flooded marsh habitat, providing adequate flows to keep eggs well-aerated and flushing out newly hatched fry.”

During late March and early April, gauge height at the New London USGS site on the Wolf River fluctuated from 6 to 7 feet during spring electrofishing survey efforts. A minimum gauge height of 7 feet is needed to get the main New London and Shiocton marshes operating, with an 8-foot gauge height being more optimal, said Nickel. Although levels were lower in early April during the peak spawn, a small flood pulse in mid-April pushed gauge heights to 8 feet. Steady increasing water temperatures followed.

“The notable YOY walleye catch in 2021 should boost the adult population, particularly if there is good survival. Since 2016, the average YOY walleye catch rate has surpassed 3.6 per trawl annually, and the adult walleye catch rate remained stable in 2021. As a result, multiple-year classes have been produced recently that will continue contributing to the adult fishery and should provide good angling opportunities,” said Nickel.

A total of 42 YOY saugers with a catch rate of 0.3 per trawl was recorded, the highest YOY sauger catch rate since 2009. Since the Sauger Rehabilitation Program ended in 2010, adult sauger numbers have decreased on Lake Winnebago and natural reproduction has been limited. The rehabilitation program included installing rock spawning reefs and stocking on Lake Winnebago from 2001-10. The goal was to enhance sauger spawning habitat and increase adult numbers to increase natural reproduction.

Although the project did increase adult sauger numbers from 0.2 per trawl in 2001 to 2.6 per trawl in 2009, natural reproduction continues to be limited, said Nickel. Catch rates for adult saugers have decreased to similar rates observed before the rehabilitation program began.

To improve the sauger situation, volunteers from Walleyes for Tomorrow led efforts for an experimental fry stocking project on the Upper Fox River from 2017-19 and 2021. Each spring, spawn is taken from ripe fish captured from Lake Winnebago, and fertilized eggs are transferred to a portable hatchery on the Upper Fox River in Berlin. Genetic samples were taken from all adults, allowing saugers captured during future years to be genetically tested to evaluate if they were from fry stockings or natural reproduction. In 2021, 58 saugers (42 YOY) were captured during trawling and 15 from spring netting, all less than 15 inches.

Following a record catch in 2020, YOY perch showed another measurable year class in 2021. The catch rate for YOY perch in 2021 was 5.1 per trawl, the fourth straight year with a catch rate greater than 3.5 per trawl. The adult catch was 9.6 per trawl, the fourth-highest adult perch catch since 1986. The high adult catch in 2021 can be attributed to yearlings from the record 2020 year class, which ran 5.5 to 7.5 inches.  Some adult fish measured up to 12.5 inches. Fish from the record year class in 2020 should begin to reach 8 to 10 inches in 2022.

Oxbow Lake

Nearest town: Oshkosh, FdL

Surface area: 131,939 acres

Max. depth: 21 feet

Water clarity: 4 feet

Fish species present:

Black crappies, white bass, bluegills, pumpkinseeds, rock bass, yellow perch, white suckers, catfish, smallmouth  bass, largemouth bass, northern pike, walleyes, muskies, and lake sturgeon.

For information:

DNR regional fisheries office (920) 424-3050, the DNR web site http://www.dnr.state.wi.us/org/water/fhp/fish, or call Fox River Bait & Tackle, (920) 233-7409.

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