Fish Management

Walleye are an incredibly important species in Wisconsin ecologically, economically, and culturally.
They’re unique in that they are a cool water low-light adapted species. While originally a river
species, Walleye were introduced to many Northwoods lakes around the turn of the 20th century.
In recent decades, however, Walleye populations have been declining in Wisconsin. This includes
both adult numbers and the number of young fish surviving their first year, a process called
recruitment. But the degree of decline varies by lake, and there’s no single factor causing it.
Instead, Walleye appear to experience a bottleneck in many lakes—where some combination of
environmental or biological factors limits how many young fish survive to adulthood.
Many studies have investigated what’s driving these changes. Two common suspects are rising
water temperatures and increasing numbers of Largemouth Bass, which are now more widespread
in Wisconsin lakes. In one notable study, scientists removed over 300,000 warm water fish,
including bass, from a lake over three years to see if Walleye would bounce back. After the removal,
Walleye did not begin to reproduce naturally in the lake. Yellow Perch populations, however,
increased sharply, though this trend was also seen (though not significantly) in a nearby reference
lake.

These findings suggest that Walleye decline isn’t being caused by bass alone. Rather, it's likely due
to a combination of factors, including climate change. Temperature plays a huge role in aquatic
ecosystems, often called the "master factor" because it influences fish growth, reproduction, and
survival. As lakes warm, studies project that Largemouth Bass will continue to thrive, while Walleye
may struggle. Models predict that by the end of the century, only about 10% of today’s Walleye dominant lakes in Wisconsin will remain so.

Another major factor affecting Walleye is overharvest. Walleye in northern Wisconsin are harvested
both by recreational anglers and by Tribal members in the Ceded Territory. Tribal harvest is a
common point of discussion, but it’s important to understand the facts. Tribal harvest is tightly
regulated and targets fewer fish than what state agencies estimate is removed by recreational
fishing. Tribal harvest also tends to focus on smaller male Walleye, which is more sustainable
because female fish are the egg producers. In contrast, recreational anglers tend to keep a higher
percentage of larger female Walleye.

Fisheries scientists have often used a benchmark of 35% of biomass removal to define overharvest.
However, it’s also important to consider production—how much new fish biomass a lake generates
each year. When we look at it this way, overharvest appears to be a more widespread problem than
previously thought.

During the talk, I also briefly shared some of my own research on Walleye habitat use. We use
archival tags, tiny data loggers surgically implanted in Walleye, to track their movement and habitat
preferences in different lakes. We've found that Walleye prefer water temperatures around 22°C
(72°F) and oxygen levels above 7 mg/L. Interestingly, they aren’t always in their preferred light
environment, likely because doing so would mean sacrificing their thermal or oxygen needs. Still,
access to these low-light habitats is critical at key times of day.

Different types of lakes restrict Walleye in different ways. This means that future management
efforts could be more successful if they’re tailored to the unique features of each lake rather than
relying on one-size-fits-all strategies. Historically, fisheries management in Wisconsin has focused
on resisting change, such as stocking Walleye to maintain populations. But many managers are
now considering other approaches, including accepting that some lakes may no longer be suitable
for Walleye, and focusing resources on lakes where Walleye are still doing well.
I included a figure at the end of the presentation that shows how different environmental factors
affect Walleye survival, especially for stocked fish. It’s a complicated topic, and many managers
could spend hours on it, but it highlights the importance of understanding lake-specific dynamics.

While many of the factors affecting Walleye populations like climate change are beyond individual
control, there are things property owners can do to help support healthy Walleye populations:

1. Reduce light pollution – Young Walleye are drawn to light, which can make them more
vulnerable to predators in shallow water. Limiting shoreline lighting at night can help.

2. Minimize use of chemicals near the lake – Pesticides and fertilizers can harm water
quality and be especially dangerous for larval fish. Reducing runoff from your property.

 

3. Protect and restore shorelines – Spawning habitat is a key limiting factor for Walleye.
Stabilizing shorelines and preserving gravel or rocky areas can promote natural
reproduction.

4. Prevent the spread of aquatic invasive species (AIS) – AIS can disrupt entire ecosystems
and reduce resources available for native fish like Walleye.

5. Eat more bass! – This one’s a bit tongue-in-cheek, but targeting abundant species like
Largemouth Bass (especially from deep, clear lakes, where they taste fantastic) can help
reduce potential competition with Walleye and free up potential food items that Bass might
have eaten.

 

And if you catch a big Walleye, consider releasing it—those large females are
vital for maintaining healthy populations.

 

I am happy to discuss any of the above points or answer any questions at – qcsmith2@wisc.edu

 

 

 

 

Two Sisters Lake has a walleye population maintained through natural reproduction and stocking.
Walleye population in 2023 was estimated to be 1,019 adults (1.4 / acre), based on the May fyke
netting of 522 adults fin clipped and the results of later electrofishing ratio of fin clipped to
unclipped (23 of 65). 93% were 15 inches or longer, largest was a 29.7-inch female.

 

Electrofishing was done June 6 and September 25, 2023.

 

2023 fyke netting and electrofishing results for:
Muskellunge 12 (67% 40 inches or longer, largest 48.6-inch female)
Northern Pike 53 (8% 26 inches or longer, largest 34.3 inches)
Largemouth Bass 470 (12% 14 inches or longer, largest 18.7 inches)
Smallmouth Bass 170 (33% 14 inches or longer, largest 19.7 inches)

 

Other Species caught:
Rock Bass, Bluegill, Black Crappie, Yellow Bullhead, Pumpkinseed, Yellow Perch, White
Sucker, Black Bullhead, Greater Redhorse, Common Shiner, Golden Shiner, Mimic Shiner,
Bluntnose Minnow, Fathead Minnow, Central Mudminnow, Logperch, Johnny Darter, Mottled
Sculpin

 

Special fishing regulations for Two Sisters Lake walleye:

 

Season Dates: May 6-March 3 Daily Bag Limit: 3 Size Limit: 18 inches
Two Sisters was stocked with 27,419 small fingerling walleye in 2023. There are no plans to stock
in 2024 to avoid competition and reduced survival of last year’s fingerlings. Stocking is planned
for next year (2025). The muskellunge population is maintained through natural reproduction.

 

As of May 8, 2024, tribal spearing results are 86 of the 87 walleye declared and 2 of the 7
muskellunge declared. 

 

 

Update In the Fall 2019 Newsletter, we introduced the concept of the WDNR Fish Sticks Program. This is an attempt to create new fish and wildlife habitat to aid the health of the fisheries in local lakes. "DNR Fish Sticks Projects are intended to restore woody habitat in lakes by adding trees to the near shore area. They are large woody habitat structures that utilize whole trees either grouped together or single trees that result in placement of more than one tree per 50 feet of shoreline. Fish Stick structures are anchored to the shore and are partially submerged near the shoreline of the lake." Several residents have expressed interest in this program but we would like to see more. Residents who are interested in utilizing part of their shoreline to help upgrade the overall fish and wildlife habitat of our lake should call John Estes at 303-941-1413 or email him at jestes7313gmail.com for information.