Category Archives: Reports

Green Bay Value Study

This is the study WFT paid for in 2018 to document the value of Sport Fishing on Green Bay.  We did this in anticipation of the commercial fishing growth in Green Bay.

WFT representatives attended 2 meetings, one in Sturgeon Bay and one in Green Bay in 2018.  Both meetings disturbed us greatly, thus the study.

The DNR has never really referenced the study. Meredith Penthorn at DNR and she said she would post it on the DNR website to make it a public document.

In an effort to better understand angling in the Bay of Green Bay watershed and how this identity impacts the state economy, the authors worked with Walleyes for Tomorrow and the Wisconsin Department of Natural Resources (WDNR). Since the WDNR continually examines the catch of anglers through a long-standing creel survey design that is used to estimate fishing pressure and success, the data collection effort for this study piggy-backed upon this creel survey design by distributing a survey packet to recreational anglers intercepted at boat launches and shore fishing areas.

Diets of Larval Walleyes in Northern Wisconsin Lakes

Nathan Jaksha1, Daniel Isermann2, & Daniel Dembkowski1

University of Wisconsin-Stevens Point1, USGS-Wisconsin Cooperative Fishery Research Unit2

Introduction

  • Walleye are an important species in Wisconsin that support both recreational hook-and-line and tribal spear fisheries.
  • Walleye recruitment has declined in some lakes that previously supported natural recruitment yet has remained stable in other lakes.
  • Recent studies suggest that a recruitment bottleneck may be occurring at or before the larval stage in lakes exhibiting declines in natural recruitment.
  • Reasons for the contrasting trends in recruitment among populations are unclear, as are mechanisms underlying the recruitment bottleneck in lakes with declining recruitment.
  • Differences in prey availability among lakes with different recruitment histories could contribute to the observed trends in recruitment.
  • Assessment of larval walleye diets from lakes with different recruitment histories could provide important insight to the role of prey resources in explaining trends in walleye recruitment in Wisconsin lakes.
Photo of an adult walleye sampled by the Wisconsin DNR

Objective

Describe diet composition of larval walleyes in northern Wisconsin lakes displaying two different recruitment histories: sustained natural recruitment (S-NR) and declining natural recruitment (D-NR).

Methods – Sampling

  • Larval  walleye sampling occurred during 2016 & 2017 on 13 lakes
    • Five of these lakes were resampled in 2018
  • Sampling started mid-May each year
    • Continued at 7-10 d intervals until early June
    • Surface temps = 11-16˚C
  • Larval walleyes were collected using a 1,000-µm mesh conical ichthyoplankton net.
    • Towed at surface (5 min) at both nearshore (within 100-m) & offshore locations (≥100-m) at night
  • Percid larvae identified to species using dichotomous keys
    • Random subset selected for genetic verification of visual species identification using PCR techniques

Methods – Diets

  • Gut contents of each fish were removed and diets were quantified using mean percent composition by number of individual diet items.
  • Zooplankton items classified to order for adult copepods and genus for cladocerans
  • Larval fish encountered in diets identified genetically using qPCR techniques
Magnified image of a zooplankton (Daphnia spp.) diet item
Magnified image of a larval Walleye

Results – All Lakes

  • Larval walleye collected from 6 S-NR lakes and 4 D-NR lakes (diets summarized in Table 1).
  • Guts were removed from 115 larval walleyes (mean TL = 11.4 mm; range = 6.4 –22.0 mm).
  • 27% of diets (31 of 115) were empty
  • 37% of diets (42 of 115) contained larval yellow perch
  • 16% of diets (18 of 115) contained zooplankton
Table 1. Mean percent composition by number and counts of prey items observed in larval walleye diets from all lakes combined.
Diet Item% CompositionCount
Daphnia spp.15.041
Calanoid Copepods1.83
Cyclopoid Copepods5.816
Bosmina spp.0.53
Larval Fish63.349
Unidentifiable13.510

Results – S-NR vs. D-NR Lakes

  • S-NR Lakes = 86 larval walleye (diets summarized in Table 2)
    • Larval walleye mean length = 11.3 mm (range = 6.5 -22.0 mm)
    • 38 % of diets (33 of 86) were empty
    • 31% of diets (27 of 86) contained larval yellow perch
    • 20% of diets (17 of 86) contained zooplankton
  • D-NR Lakes = 29 larval walleye (diets summarized in Table 2)
    • Larval walleye mean length = 12.4 mm (range = 7.8 -21.0 mm)
    • 28% of diets (8 of 29) were empty
    • 52% of diets (15 of 29) contained larval yellow perch
    • 3% of diets (1of 29) contained zooplankton
Table 2. Mean percent composition by number and counts of prey items observed in larval walleye diets from S-NR and D-NR lakes.
Recruitment History:S-NR LakesD-NR Lakes
Diet Item% CompositionCount% CompositionCount
Daphnia spp.19.1404.81
Calanoid Copepods2.530.00
Cyclopoid Copepods8.1160.00
Bosmina spp.0.730.00
Larval Fish60.13471.415
Unidentifiable9.4523.85

Discussion

  • Larval yellow perch were the dominant prey item for larval walleyes in lakes exhibiting both sustained and declining natural recruitment.
    • Extent of piscivorymuch greater than previously assumed
  • In general, larval walleyes in S-NR lakes consumed a greater diversity of prey items and more zooplankton than larval walleyes in D-NR lakes.
  • Further statistical analyses required to determine if diets and prey availability differed between S-NR & D-NR lakes.

Acknowledgements

  • This study was funded by the Wisconsin Department of Natural Resources through the Fisheries Analysis Center at the University of Wisconsin-Stevens Point.
  • Jason Gostiaux
  • Walleyes for Tomorrow: Research Fellowship

Flexible Classification of Wisconsin Lakes for Improved Fisheries Conservation and Management

Successful fisheries management practices developed for one ecosystem can often be used in similar ecosystems. We developed a flexible lake classification framework in collaboration with ~100 fisheries biologists for improved fisheries conservation management in Wisconsin, USA. In total, 5,950 lakes were classified into 15 lake classes using a two tiered approach. In tier-one, lakes were clustered into “simple” and “complex” sportfish assemblages. In tier-two, lakes were further clustered using accumulated degree days, water clarity, and special cases. We focus on temperature and clarity because these factors often drive fisheries change over time — thus a lake’s class can change over time. Lake class assignments were refined through a vetting process where fisheries biologists with expert knowledge provided feedback. Relative abundance, size-structure, and growth rates of fishes varied significantly across classes. Biologists are encouraged to utilize class interquartile ranges in fisheries metrics to make
improved fisheries assessments. We highlight hard-won lessons from our effort including: (1) the importance of co-developing classification frameworks alongside fisheries biologists; and (2) encouraging frameworks where lakes can shift classes and fisheries expectations over time due to factors like climate change and eutrophication.

2017-18 Winnebago System Walleye Report

Attached is the 2017 Winnebago Walleye Report. The report covers a variety of topics including 2017 spring water level and walleye hatch results, 2017 spring adult spawning stock results, walleye exploitation and reward tag study results, a walleye population outlook, and a regulation change discussion update.

Walleye anglers have enjoyed some productive walleye fishing on the Winnebago System over the last few months, particularly in May and June. Many anglers have also been wondering how the 2018 walleye hatch will stack up after the historical spring weather events that swept through the area (you may remember the 30 inch snow event in April). DNR staff and a host of local volunteers completed the first round of the Annual Lake Winnebago Bottom Trawl Assessment last week.

Preliminary results indicated a measurable 2018 walleye hatch (5.7 young of year/trawl), but we will have to wait until the September and October trawling rounds are completed for official results. The survey is also vital for evaluating the year class strength of other sport and forage fish species in Lake Winnebago. Stay tuned for the annual trawling report once the survey concludes in fall. I hope you enjoy the walleye report and good luck with your summer fishing adventures. We are committed to service excellence.

Visit our survey at http://dnr.wi.gov/customersurvey to evaluate how I did. Adam D. Nickel Phone: (920) 424-3059 adam.nickel@wisconsin.gov

Click here for 2017-18 Winnebago System Walleye Report

2016 Lake Winnebago Bottom Trawling Assessment Report

2016 Lake Winnebago Bottom Trawling Assessment Report
Adam Nickel, Winnebago System Gamefish Biologist, January 2017

The 2016 Winnebago bottom trawling survey results are in and it was a great year to be on the boat as the survey revealed strong year classes for crappie, walleye, and forage base species. Over 36 volunteers (a mix of new and veteran) boarded the Calumet in 2016 and donated over 400 volunteer hours of labor. The bottom trawl assessment is the most critical fisheries assessment conducted on the Winnebago System and simply could not be conducted without the help of our dedicated volunteer base.

The objectives of the trawling assessment are to:
1) provide critical information on year class strength of game and nongame fish species,
2) monitor trends in the forage base,
3) monitor general population trends of game and nongame fish species. The survey also provides volunteers with a hands-on experience with
conducting survey work on the system.

Full report details are here

Walleye Movement in the Winnebago System (2011-2013)

I attended the Berlin chapter meeting last night and had some interesting conversation. Today I called Adam Nickle our Fisheries Biologist. The attached PDF document is a report on a walleye tracking study DNR conducted with WFT funding. WFT purchased the sonic tags. Much of the Berlin conversation centered around lack of walleye using the Fox River as a spawning area.

As you can see from the text, the Winnebago System has 35 listening devices installed. These are used to track sturgeon primarily but are also used to track walleye, flathead catfish and musky. The System is so large and dynamic that this system has been very beneficial to understand how important fish species move around on an annual basis.

Walleye Movement in the Winnebago System (2011-2013)

 

See

Report from Green Lake

image1After several outboard motor issues, we set seven nets the evening of the twenty-second. In cooperation with the local DNR biologist who are currently performing their five year warm water fish survey, we are running three of their nets so we actually have ten nets to work.

We got three net-nights under our belts. We have handled 137 walleyes, with 38 of which were “workable” females (nothing over 26″ do we strip, this also accounts for green females – all these fish were documented then released) to 61 lively always ready boys – decent ratio.

We have 3’072’000 future walleye dinners/wall-hangers incubating. Hatching of those eggs will begin about 5/12 with full hatching on 5/16. Target is around 9’300’000 eggs, with a target release number of 7’500’000. We’ll see how it all goes, we’ve got a great hatchery attended – should go fine.

Peshtigo Flowage – Walleye Spawning Reef

Here are a bunch photos for the Peshtigo Flowage – Walleye Spawning Reef project