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7-1
Section 7
About Aquatic Invasive Species
The Great Lakes...darkly reflect how a global
tradefest can turn into an ecological makeover. What
was once a distinct North American body of water...is
now little more than a degraded multicultural
aquarium.
—Andrew Nikiforuk, Pandemonium1
Introduction Section 7 describes the aquatic invasive species
(AIS) that are living in or near Lac du Flambeau and
presents data from a survey on residents’
perceptions of AIS.
People transport organisms around all the time.
Sometimes when a non-native species is brought
into a new area the species will take over and
spread rapidly and widely throughout the area.
When this happens, the spread can cause major
harm to the native ecosystem or humans. When
non-native plants, animals, or pathogens rapidly
take over a new location and alter the ecosystem,
they are called invasive species.4
There is little doubt that AIS have negative impacts
on Wisconsin.5 AIS are one of the newer threats to
Wisconsin lakes, and residents spend several million
dollars each year trying to control AIS, costs that are
increasing every year.6
Of the many dozens of AIS that now make their
homes in Wisconsin, several have found their way to
Vilas County and other counties near Lac du
Flambeau, and even to the lakes and wetlands of
Lac du Flambeau (Table 7-1 and Table 7-2).
Table 7-1. Presence of AIS Near or in Lac du Flambeau*
AIS Oneida County
Price County
Vilas County
Iron County LdF
Banded Mystery Snail X X X X X
Chinese Mystery Snail X X X X X
Curly Leaf Pondweed X X X X
Eurasian Water Milfoil X X X X
Freshwater Jellyfish X X X X
Purple Loosestrife X X X X X
Reed Canary Grass X X
Rusty Crayfish X X X X X
Smelt X X X
Spiny Waterflea X X
*Data from variety of WDNR reports January 2014
The waters of Lac du Flambeau are clearly at risk.
Several lakes have infestations of rainbow smelt,
purple loosestrife, or rusty crayfish, while other AIS
like Eurasian water milfoil and curly-leaf pondweed
are moving ever closer. In the past few years curly-
leaf pondweed was found in Island Lake in
Manitowish Waters and in Lost Lake in St. Germain
in Vilas County, and on the Rainbow Flowage in
Oneida County; Eurasian water milfoil was found in
Kentuck Lake in Vilas County; zebra mussels were
found in Keyes Lake in Florence County; and the
Friends I am a boater, and like you I love our lakes.
I've been hearing about these aquatic invaders in
our state.
Non-native plants and animals, threaten waters
far and wide.
They’d love to make their way into a lake they’ve
never tried.
—Partial lyrics for the folk song, The Ballad of Aquatic Invasive Species, Scott Gatzke2
Wisconsin Statute Section 23.22 (1) (c) officially
defines invasive species as “nonindigenous species
whose introduction causes or is likely to cause
economic or environmental harm or harm to human
health.”3
7-2 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Chinese mystery snail was confirmed in Little
Crawling Stone Lake and Pokegama Lake in Lac du
Flambeau. As recently as 2013, Eurasian water
milfoil was found in Smokey Lake in Phelps and in
Lost Lake in St. Germain, and, in 2014, the spiny
waterflea was found in Trout Lake.7
Despite the prevalence of Eurasian water milfoil and
curly-leaf pondweed in Vilas County and counties
nearby, Lac du Flambeau is currently free of them
and the problems associated with them. Even so,
their presence nearby has fueled apprehension that
these and other AIS may eventually infest lakes and
wetlands in Lac du Flambeau, harming local
ecosystems, native plant species, and traditional
gathering resources while threatening human health,
the economy, and property values.
There is concern, too, that climate change could
increase the probability that new introductions of AIS
may replace native aquatic plants while
exacerbating the spread of AIS already in the area,
again at the expense of native plants.8
Table 7-2. Aquatic Invasive Species in Lac du Flambeau Lakes*
Waterbody Smelt Rusty
Crayfish Purple Loose-
strife*** Fresh Water
Jellyfish
Chinese Mystery Snail
Banded Mystery Snail
Reed Canary Grass
Big Crawling Stone Lake** 1975 1986
Fence Lake** 1968 2007 2010
Gunlock Lake 2008 2007
Flambeau Lake** 1968 2008
Ike Walton Lake**
Little Crawling Stone Lake** 1982 2002 2011 2010
Little Trout Lake** 1990 X X
Long Interlaken Lake** 1983 2013 2013
Lower Sugarbush X
Middle Sugarbush X X
Moss Lake** 1989 X
North Twin Placid Lake 1996
Pokegama Lake** 1996 1986 2011
Powell Marsh** X
Shishebogama Lake X 2010
South Twin Placid Lake X
Squaw Lake 1963 1961 2004
Toto Tom Lake 1990 X
Upper Sugarbush 1975
White Sand Lake** 2002 2008 X
Wild Rice Lake 1975 2010 2010 2006
*Table compiled from several WDNR reports of January 2014. X = date unknown **Focus of the Bear River Watershed Comprehensive Lake Management Plan ***Information for Purple Loosestrife from WDNR & Lac du Flambeau reports
Section 7: About Aquatic Invasive Species 7-3
Bear River Watershed Comprehensive Lake Management Plan
Aquatic Invasive Species Mystery Snails There are three species of mystery snails in
Wisconsin, (Chinese mystery snail, banded mystery
snail, and brown mystery snail, but only the brown
mystery snail is native to Wisconsin.9
In Lac du Flambeau presently, the Chinese mystery
snail (Figure 7-1) is in Little Crawling Stone,
Gunlock, Long Interlaken, Pokegama,
Shishebogama, Squaw and Wild Rice Lakes, and
the banded mystery snail (Figure 7-2) is in Fence,
Little Crawling Stone, Long Interlaken,
Shishebogama, South Twin Placid, and Wild Rice
Lakes (Table 7-2).
Not much is known about these invasive snails,
though it appears they have a negative effect on
native snail populations. Their large size and hard
operculum (a trap door cover which protects the soft
flesh inside) and their thick hard shell make them
less edible for predators, like rusty crayfish, an
invasive widely spread throughout Lac du
Flambeau.10
The Chinese mystery snail came from southeast
Asia, Japan, and eastern Russia, where it is a food
source, while the banded mystery snail is native to
North America.11
The Chinese mystery snail is believed to have been
sold originally in a Chinese food market in San
Francisco in the late 1890s; collected and used as
early as 1914 in Boston; and likely released from
someone’s aquarium into the Niagara River
sometime between 1931 and 1942.12
The banded mystery snail was likely spread by an
amateur conchologist who purposefully released
around 200 of the snails simultaneously into the
Hudson River. The snail probably dispersed by itself
following this event, but more recent introductions
were likely made via release from aquaria.13
Figure 7-1. Chinese Mystery Snail
Figure 7-2. Banded Mystery Snail
Little is actually known about either of the invasive
snails, including their sex life. The snail is a mystery
because in the spring when it gives birth, its young
are fully-developed snails that suddenly and
mysteriously appear.14
There has been much discussion among scientists
on whether the banded mystery snail is a potential
carrier of the swimmer’s itch parasite, but to date no
banded mystery snails have been found carrying the
parasite.15
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Bear River Watershed Comprehensive Lake Management Plan
Mystery snails thrive in silt and mud areas although
they can be found in lesser numbers in areas with
sand or rock substrates. They are found in lakes,
ponds, irrigation ditches, and the slower portions of
rivers and streams. They are tolerant of pollution
and often thrive in stagnant water areas.16
Lakes with high densities of mystery snails often see
large die-offs of the snails which are related to the
lake’s warming and resulting low oxygen (related to
algae blooms).17
Despite being classified as an invasive, mystery
snails are still available for sale through the internet
to aquarium enthusiasts who rely on them to keep
tanks free of unwanted algae.18
Curly-Leaf Pondweed Curly-leaf pondweed (Figure 7-3 and Figure 7-4) is a
non-native submerged aquatic plant that has a
unique ability to thrive in cool water, allowing it to
out-compete other aquatic plants.19
The plant is
currently not in any lake in Lac du Flambeau, though
it is in lakes in Vilas County and other counties
nearby (Table 7-1).
Figure 7-3. Curly-Leaf Pondweed
Figure 7-4. Infestation of Curly-Leaf Pondweed
Curly-leaf pondweed is one of 80 pondweed species
found throughout the world. It is native to the fresh
waters of Eurasia, Africa and Australia.20
The plant was accidentally introduced into the
United States when the common carp was brought
here during the mid 1800s. It is thought to have
made its way to Wisconsin in 1905 along with fish
imported from Europe.21
Curly-leaf pondweed has a unique life cycle. Unlike
most native aquatic plants that come out of
dormancy in spring and reach their maximum growth
in late summer or early fall, curly-leaf pondweed
normally begins growing in the fall.22
Depending on snow cover and winter severity, curly-
leaf pondweed may be dormant or actively growing
under ice. Its natural inclination for low water
temperatures helps it avoid competition with other
plant species. Its fast early spring growth allows the
stems to reach the water’s surface before any other
plant, and by late spring, a dense canopy of curly-
leaf can form, blocking sunlight from reaching other
native plants (Figure 7-5).23
Figure 7-5. Infestation of Curly-Leaf Pondweed
Curly-leaf pondweed plants usually complete their
life cycle in June or July, when they die back,
forming large mats of dying vegetation on the
surface which release nutrients such as phosphorus
into the water, fueling algal blooms.24
Turions and seeds are formed on the plants before
they die. A turion (Figure 7-6) is a dormant shoot
Section 7: About Aquatic Invasive Species 7-5
Bear River Watershed Comprehensive Lake Management Plan
segment (vegetative bud) that can form almost
anywhere on the plant. It is a hard structure that
looks a little bit like a burr or pinecone.25
Figure 7-6. Turion of Curly-Leaf Pondweed
Although the plants also produce seeds, the turions
are likely its most reliable form of reproduction. The
turion falls to the bottom of the lake as the plant dies
and begins to decay. Most of the turions begin to
sprout in fall, responding either to the shortening day
length or to water temperature. However, some
turions will actually sprout in the spring and some
will lie dormant in the sediment until environmental
conditions are favorable for sprouting. Turions can
remain dormant for years.26
For the plants that sprout in the fall, the initial growth
form is a winter foliage that stays green, sometimes
dormant or sometimes actively growing, even under
the ice. The curly-leaf pondweed foliage in winter to
early spring are quite narrow and lack the wavy
edges.27
A few days after ice-off, curly-leaf pondweed begins
to grow more rapidly and attain its spring foliage
(lasagna noodle-like wavy, hairy edges with a crispy
appearance). Turions that sprout in the spring also
have narrow non-wavy leaves when the plant first
sprouts, then the wavy leaves develop as the plant
matures.28
Eurasian Water Milfoil Eurasian water milfoil (EWM) is a submerged
aquatic plant that poses a serious threat to a lake’s
native aquatic plants and the animals that depend
on diverse ecosystems.29
EWM (Figure 7-7) is not
currently in any lake in Lac du Flambeau, but it is
found in Vilas County and other nearby counties
(Table 7-1).
Figure 7-7. Comparison of EWM with the Native Northern Water Milfoil
There are 11 native water milfoil species in North
America. Of these, seven are native to Wisconsin.
The native water milfoils are not as aggressive as
the exotic water milfoil and they have natural
predators. Some Wisconsin species of water milfoil
are quite rare and are on the Wisconsin Threatened
and Endangered species list.30
EWM can form thick underwater stands of tangled
stems and vast mats of vegetation at the water’s
surface. It can crowd out native plants and become
so thick that the larger fish cannot swim through the
tangled mats. When EWM mats get well established,
channels are needed to allow access from the
shoreline out into deeper water areas. EWM is now
one of the most troublesome submerged aquatic
plants in Wisconsin.31
EWM is native to Europe, Asia, and northern Africa.
It may have been brought in to the United States via
aquaculture and the aquarium trade. The first
authenticated record of EWM in the United States
was in 1942 in a Washington D.C. pond. In 2007 it
was found in 48 of the 50 states. EWM was first
documented in Wisconsin in the 1960s.32
EWM is an evergreen plant that remains alive over
the winter and starts growing when water tempera-
tures reach 50oF. EWM begins growing earlier in the
season than the native water-milfoils, making early
spring chemical treatment an option for its control.33
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In spring and summer, EWM can grow up to two
inches a day in water depths ranging from less than
one foot to over 20-feet. Thick beds can form in
water depths from 3 to 20 feet deep, but most
commonly reach nuisance levels in water depths of
6-15 feet.34
If EWM plant growth reaches the surface of a lake,
the plant will continue to grow and can form a
canopy over the surface (Figure 7-8), making the
area nearly impassable for a motor boat and
interfering with swimming and fishing, as well as
shading out native plants.35
Figure 7-8. Infestation of Eurasian Water Milfoil
Unlike curly-leaf pondweed, EWM does not produce
turions. EWM produces seeds and runners, but the
main method of plant spread is through dispersal of
plant fragments by boats and wave action.36
In the late summer and early fall, auto fragmentation
may occur, when the plant breaks itself into smaller
pieces. Plant cells at leaf nodes and side-branch
connections become weak, die, and break off. The
newly formed fragments float to new locations where
they fall to the substrate, root, and establish new
beds of EWM (Figure 7-9).37
Figure 7-9. Eurasian Water Milfoil Fragmentation
EWM has been known to hybridize with northern
water milfoil. The hybrids cannot be easily
distinguished by visual characteristics, but rather
have to be identified through DNA analysis.38
Freshwater Jellyfish The freshwater jellyfish (Figure 7-10 and Figure
7-11) found in Wisconsin are one of several species
native to China. They were first reported in North
America as early as 1884, and in Wisconsin in
1969.39
The freshwater jellyfish found in Lac du
Flambeau are in Middle Sugarbush Lake and White
Sand Lake (Table 7-2).
Figure 7-10. Freshwater Jellyfish
Adventitious roots
Section 7: About Aquatic Invasive Species 7-7
Bear River Watershed Comprehensive Lake Management Plan
Figure 7-11. Freshwater Jellyfish
Although they probably evolved from descendants of
ocean jellyfish, little is known about the evolution of
freshwater jellyfish, largely because they leave no
fossil records.40
William Sowerby (1827-1906), Director of the Royal
Botanic Gardens in Regent’s Park, just outside
London, England, found male jellyfish swimming in a
large, water-lily tank among the sediments and the
root crowns of pickerelweeds only three weeks after
filling the water tank. Thinking they came from South
America with the plants, he dubbed them Amazon
jellyfish.41
In 1884, mature jellyfish polyps were found in a
water tank at Regent’s Park, and that same year,
immature polyps were found in a stream in
Pennsylvania.42
The freshwater jellyfish probably landed at both
locations as polyps or cysts attached to sediments,
water plants, or fishes. At the time – the Victorian
Era of the 1880s – maintaining water gardens and
stocking carp were the rage, and garden clubs and
aquarium societies were busy gathering the world’s
exotic plants and fishes for display and study.43
The jellyfish soon made their way to other botanical
societies, as well as to public and private aquariums
throughout England, Europe, North America, South
America, and Australia. Some were flushed into
lakes and rivers when aquariums were emptied, and
swept downstream to new waters. Others may have
hitched rides on the backs of turtles or the feet of
water birds, perhaps they even stuck to boats and
boat motors.44
After appearing in Pennsylvania waters, jellyfish
progressively moved to other states and provinces.
By the time they were first sighted in Wisconsin, they
had already been reported in 33 states, the U. S.
Territory of Hawaii, and Washington DC.45
Wood ducks have been credited, or blamed, for
introducing jellyfish to Wisconsin when they visited a
farm pond near Baraboo, Sauk County. By 2006,
jellyfish sightings had been reported for 37 natural
lakes, two dugout ponds, and one creek.46
These “jellyfish waters” vary in size from tiny ponds
to lakes of 9,842 acres (Lake Mendota) and lakes
that are 236 feet deep (Big Green Lake).47
The freshwater jellyfish has been found in a variety
of water types. They have been observed in waters
ranging from crystal clear rock quarries to soupy
green farm ponds. Preliminary research indicates
that waters high in chloride do not favor colonization
by the freshwater jellyfish.48
The extent to which freshwater jellyfish are
impacting lakes is not known. Speculation exists,
however, that since jellyfish eat zooplankton (which
are normally eaten by small fish), some negative
impacts may be taking place.49
Rusty Crayfish Rusty crayfish (Figure 7-12) are in at least eleven
lakes in Lac du Flambeau (Table 7-2). They are
native to streams in the Ohio River Basin states of
Ohio, Kentucky, Illinois, Indiana, and Tennessee.
They were likely introduced to Wisconsin waters by
anglers who used them as live bait.50
7-8 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Figure 7-12. Rusty Crayfish
In Wisconsin lakes, the rusty crayfish can impact
native crayfish populations, aquatic plant
communities, and consequently entire lake
ecosystems.51
Rusty crayfish are aggressive and will chase native
crayfish from their prime habitat. When native
crayfish are chased out into the open, they are more
susceptible to predation by large fish. The rusty
crayfish consequently displace the native crayfish
and often reach high densities.52
Rusty crayfish eat small fish, insects, fish eggs, and
aquatic plants. They eat about four times the amount
of food a native crayfish eats. They are considered
messy eaters because when they snip off a plant to
eat, they often only eat small pieces of the plant and
the remainder of the plant floats away. If rusty
crayfish are eating Eurasian water milfoil, they can
actually spread the water-milfoil with their eating
habits.53
There are 330 native crayfish species in the United
States, of which 111 species are in peril of
extinction. Native crayfish are important members of
aquatic ecosystems in Wisconsin. They perform
many functions, including processing detritus and
serving as food for game fish.54
Mature rusty crayfish mate in late summer, early fall,
or early spring. The male transfers sperm to the
female, which she then stores until her eggs are
ready to be fertilized, typically in the spring (late April
or May) as water temperatures begin to increase.55
The stored sperm are released as eggs are expelled
and external fertilization occurs. The eggs attach to
swimmerets (small, leg-like appendages under the
tail). Just prior to egg laying, white patches will
appear on the underside of the female’s abdomen
(“tail section”), especially on the tail fan. These white
patches are glair, a mucus-like substance secreted
during egg fertilization and attachment. Rusty
crayfish females lay from 80 to 575 eggs.56
Eggs hatch in three to six weeks, depending on
water temperature. Once hatched, young crayfish
cling to the female’s swimmerets for three to four
molts (molting is when crayfish shed their old shell to
allow growth). Young crayfish may stay with the
female for several weeks for protection. Eventually
the young leave the female, and then undergo eight
to ten molts before they mature.57
Rainbow Smelt Rainbow smelt (Figure 7-13 and Figure 7-14) are a
small (7 to 9 inches long, weighing 3 ounces)
invasive fish. They are silvery overall with a pale
green back and iridescent purple, blue and pink on
their sides. They have a conspicuous silvery streak
running lengthwise along each side. In the water,
rainbow smelt shimmer colorfully. When removed
from the water, however, they quickly fade to a
silvery white and give off the odor of cucumbers.58
Figure 7-13. Rainbow Smelt
Section 7: About Aquatic Invasive Species 7-9
Bear River Watershed Comprehensive Lake Management Plan
Figure 7-14. Rainbow Smelt
The rainbow smelt is not native to the Great Lakes.
The smelt is a saltwater species, though a
freshwater population exists in Green Lake, Maine.
Fish from this population were stocked into Crystal
Lake, Michigan in 1912. Some of the fish escaped
from Crystal Lake and were first caught in Lake
Michigan in 1926.59
Once established, the smelt population expanded
rapidly in Lake Michigan, becoming very abundant in
the 1930s. The smelt was nearly eliminated from the
lake in 1941–1942 by an unknown pathogen.
However, by the mid-1950s and into the 1960s the
fish were once again highly abundant.60
Smelt have been present in Wisconsin waters of the
Great Lakes for over 70 years, first discovered in
1928 in Little Sturgeon Bay in Door County. Through
the intentional or accidental efforts of private
individuals, smelt began to spread to Wisconsin’s
inland waters in the 1980s.61
Lac du Flambeau
currently has twelve lakes confirmed to have
rainbow smelt; Crawling Stone Lake being the first in
1975, and Pokegama and North Twin Placid Lakes
in 1996 (Table 7-2).
Few smelt live beyond five years of age. Both sexes
become sexually mature at about two years of age.
A female may produce 33,000 to 75,000 eggs in one
season, depending on her size. The spawning
season takes place in early spring. Larvae and
juveniles feed upon zooplankton, particularly
microscopic crustaceans. Adult smelt feed on small
crustaceans and fish.62
Fish biologists have clear data showing distinct
negative impacts of smelt on the sport fish
populations of Wisconsin’s inland lakes. For
example, smelt compete directly with juvenile
walleye for food, which may be a principal
mechanism in limiting walleye recruitment. They
compete with other native fish for food as well. Smelt
will even eat other fish in their early or larval life
stages. These larval fish or fry can include lake trout,
whitefish, walleye and cisco, a forage species native
to Wisconsin.63
The Tribal fish hatchery raises and stocks brown
trout to counter the influence of the rainbow smelt,
an invasive fish that can cause serious harm to the
walleye fishery in Lac du Flambeau. Rainbow smelt
and walleye inhabit the same spawning areas, but
the smelt tend to arrive first to lay their eggs. When
hatched, the smelt may eat the eggs of the newly
arrived walleye as well as the zooplankton that
walleye fry would ordinarily eat. The young smelt
then move to the deeper water where they and adult
smelt eat what would ordinarily be available for the
walleye when they arrive later. The life-cycle of the
brown trout is such that when they are introduced to
the lake, they dine on the smelt and serve as a
biological control favoring the walleye.64
There is some evidence that the rate mercury
accumulates in top level fish consumers accelerates
when they switch to a diet of smelt. Rainbow smelt
are also rich in thiaminase, an enzyme that destroys
thiamin, which is necessary for development of fish
embryos. As lake trout and other sport fish consume
the smelt, their ability to successfully reproduce
diminishes because of thiamin deficiency.65
Waterfleas The spiny waterflea and fishhook waterflea (Figure
7-15) infest lakes in Vilas County, but not in Lac du
Flambeau (Table 7-1).
7-10 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Figure 7-15. Spiny and Fishhook Waterfleas
Spiny and fishhook waterfleas are often first noticed
by anglers when the invasives become entangled on
fish lines (Figure 7-16), anchors, downrigger cables,
and other types of gear used in boating activities.66
Figure 7-16. Spiny Waterfleas on Fishing Line
In addition to causing problems for anglers and
recreational users, the invasive waterfleas have the
potential to disrupt food webs.67
Spiny and fishhook waterfleas are large (up to ¾
inch) predatory crustacean zooplankton that eat
smaller zooplankton, including Daphnia (native
waterfleas). This puts them in direct competition with
young fish that also eat native zooplankton.68
Like juvenile fish, spiny and fishhook waterfleas will
“stalk” their prey. And, like most invasive species,
they lack predators that can keep their population in
check. Young fish have trouble eating the spiny and
fishhook waterfleas due to their long, spiny tails.69
Spiny and fishhook waterfleas are native to parts of
Europe and Asia. Both species of waterfleas entered
the Great Lakes in ship ballast water from Europe.
The spiny waterflea arrived in the 1980s, followed in
the 1990s by the fishhook waterflea. One or both
species are now found in all of the Great Lakes.70
Their resting eggs can survive long after the adults
are dead, so the eggs, as well as the waterfleas,
may be transported via water between an infested
lake to a non-infested lake.71
Reproductive females carry their offspring on their
backs in a balloon-like brood pouch, which can be
filled with either developing embryos or resting
eggs.72
Most of the time, female spiny and fishhook
waterfleas exhibit rapid asexual reproduction where
females produce from one to ten eggs that are able
to develop into new females without mating or
fertilization. The new females are genetic replicas, or
clones, of the mother. The generation time of this life
cycle (embryo to adult female) varies with water
temperature because rates of metabolism rise and
fall with temperature.73
During the summer, when the surface water of the
lake is warm, waterfleas can produce a new
generation in less than two weeks. Since males are
not needed for reproduction, they are rarely found
when food is plentiful or when environmental
conditions favor rapid population growth.74
For spiny and fishhook waterfleas, sex of offspring is
not determined genetically, but rather by
environmental factors. When food becomes limited
or when the lake cools in the fall, males begin to
appear. Declining environmental quality can be
sensed by adult females, who respond by producing
male rather than female offspring. These males are
able to mate with surviving females, producing
resting eggs. The resting eggs are first carried as
orange-brown spheres in the female brood pouch.
They are later released and fall to the lake bottom
where they can survive the cold winter. In spring or
early summer, these eggs hatch into juvenile
females that begin the asexual reproduction again.75
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Bear River Watershed Comprehensive Lake Management Plan
Resting eggs can remain dormant for long periods of
time, and they offer an explanation for the arrival of
spiny and fishhook waterfleas in North America.76
Reed Canary Grass Reed canary grass (Figure 7-17) is found in 500,000
acres of wetlands, moist meadows, and riparian
areas throughout Wisconsin.77
In Lac du Flambeau,
it is in the Powell Marsh and near Little Trout Lake
(Table 7-2).
Reed canary grass is the “poster plant” for disturbed
wet sites. It forms dense stands in places where
clearing, grading, siltation, filling, or other disruptions
have created an opening with moist soil. A Eurasian
strain has been used for erosion control and lowland
pastures, but its aggressive growth has made it a
threat to native wetland plants.78
Reed canary grass is one of the first grasses to
appear in the spring and can grow 6-7 feet above
the soil surface. It reproduces by seed, by stem
fragments, and horizontal stems (rhizomes).79
Reed canary grass is one of the first wetland plants
to emerge in the spring, enabling it to shade out
native species that emerge later in the growing
season. It can stay green and actively growing well
past the first killing frost in autumn.80
Reed canary grass seeds and rhizomes readily float,
making streams and ditches networks for effective
dispersal by humans and wildlife. The seeds readily
adhere to moist skin or fur and are transported by
clothing, equipment, and vehicles.81
Yellow Flag Iris Yellow flag iris (Figure 7-18) is a beautiful, robust,
showy plant that is native to Europe, British Isles,
North Africa, and the Mediterranean Region.82
Currently, it is not found in Lac du Flambeau (Table
7-1).
Figure 7-18. Yellow Flag Iris
Yellow flag iris is also known as yellow Iris, water
flag, European yellow-Iris, and pale yellow iris.83
Yellow flag iris grows fast and spreads rapidly. Its
roots establish dense mats that support thickets of
three to six foot plants in shallow water along the
shorelines, crowding out beneficial native plants. It
spreads within an established site through root
growth, and to new locations by dropping seeds into
the water.84
While very young plants can be removed by hand-
digging or pulling, removing mature
plants typically requires equipment
that is likely to cause considerable
ground disturbance and increase the
potential for shoreline erosion.85
All parts of the plant are poisonous,
limiting the source of food for wildlife
in the areas where it dominates.86
There are presently no known
biological agents for effectively
Figure 7-17. Infestation of Reed Canary Grass
7-12 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
controlling yellow flag iris. There are suitable
herbicide options, but only chemicals approved by
the Wisconsin Department of Natural Resources
may be applied and then only by licensed
professionals with a WDNR permit.87
Purple Loosestrife Purple loosestrife (Figure 7-19) is an invasive
perennial that has spread rapidly in North American
wetlands, shorelines, and roadside ditches. Lac du
Flambeau has several infestations of the plant. See
Section 6 of this document for details.
Thick stands of
purple loosestrife
crowd out native
plants and reduce
food, shelter, and
nesting sites for
wildlife, birds,
turtles, and frogs.
Purple loosestrife
was introduced to
the United States
in the 1800s in
discarded soil and
water that had
been used for ship ballast. The plant, too, was
imported to sustain bee keeping and gardening
businesses. This European species has since
invaded nearly every U.S. state and at least six
Canadian provinces.
Due to the prevalence of infestations in Lac du
Flambeau, the Tribal Natural Resources Department
and the Town Lakes Committee have worked
together to control the infestations.
Results of Community Survey The process used to prepare the Bear River
Watershed Comprehensive Lake Management Plan
included mailing a survey to 3,000 households in
Lac du Flambeau. The survey posed questions
about topics like residents’ perceptions of the quality
of lake water, fishery, and overall environment;
current and ideal shoreline landscaping; interests in
attending a variety of workshops; and knowledge of
Aquatic Invasive Species and aquatic plants.88
Almost one-third (996 of 3,000) of the surveys were
returned completed, representing fifty-one lakes. Of
the 996 completed surveys, 576 are from
households affiliated with the ten lakes of focus in
the Bear River Watershed Comprehensive Lake
Management Plan.89
The remainder this section presents the survey
results for the questions related to aquatic invasive
species.
In order to help establish the extent to which
residents are knowledgeable about AIS, the survey
asked residents whether they had heard about AIS
prior to reading the survey.
Other than for Little Trout Lake, Flambeau Lake, and
Pokegama Lake, approximately one-third (Table
7-3) of the respondents indicate they had prior
knowledge of AIS.
Table 7-3. Prior Knowledge of AIS
Lake # Surveys Completed
# of YES Responses
% of YES Responses
Big Crawling Stone 96 33 34%
Little Trout 3 0 0%
Fence 123 43 35%
Long Interlaken 31 10 32%
Flambeau 54 10 19%
Moss 27 10 37%
Ike Walton 23 8 35%
White Sand 102 34 33%
Little Crawling Stone 34 10 29%
Pokegama 83 13 16%
Bear River Totals 576 171 30%
Figure 7-19. Purple Loosestrife
Section 7: About Aquatic Invasive Species 7-13
Bear River Watershed Comprehensive Lake Management Plan
The survey asked the residents who indicated they
had prior knowledge of AIS to identify from a list of
items, such as water quality and native fish, what
they believe is threatened by AIS.
Table 7-4 shows the percentages of responses for
each lake as well as totals for all ten lakes. For
example, of the 33 respondents for Crawling Stone
Lake, 42% believe that AIS threaten lake water
quality, 55% believe that AIS threaten native fish,
and so on.
Residents who had indicated that they had prior
knowledge of AIS were also presented with a list of
AIS and asked to identify which of them, if any, they
believe are currently in the lake (Table 7-5).
In addition to showing the percentages of
respondents who believe that particular AIS are
present in the lake, the table shows whether the AIS
are actually in the lake. For Crawling Stone Lake for
example, 18.2% of the respondents believe that the
banded mystery snail is in the lake, though in
actuality it is not.
The questionnaire asked residents who had
indicated that they had prior knowledge of AIS if they
have been taking time to look for AIS in the lake.
Table 7-6 shows the percentages of time that
respondents said they have been spending looking
for AIS. Of the 31 respondents for Crawling Stone
Lake, for example, 38.7% have not looked for AIS,
29% have looked once a season, 9.7% monthly,
9.7% weekly, and 12.9% daily.
The questionnaire asked residents who had
indicated that they had prior knowledge of AIS about
the extent to which they are concerned about AIS.
Table 7-7 shows the percentages of degree of
concern about AIS. Of the 33 respondents for
Crawling Stone Lake, for example, 36.4% are
extremely concerned about AIS, 51.5% are
somewhat concerned, 3% are not too concerned,
and 5% are unsure.
Table 7-4. Lake Resident Survey on Lakes Perceived to be Threatened by AIS
Lake #
Respondents
Lake Water Quality
Native Fish
Native Aquatic Plants
Native Shoreline
Plants Amphibians Wetlands Crustaceans Air
Quality Other
Big Crawling Stone 33 42% 55% 36% 33% 33% 33% 33% 6% 3%
Little Trout 0 0 0 0 0 0 0 0 0 0
Fence 43 49% 40% 37% 21% 9% 12% 7% 0% 5%
Long Interlaken 10 40% 20% 10% 10% 10% 0% 20% 0% 10%
Flambeau 10 40% 40% 20% 40% 40% 20% 30% 20% 0%
Moss 10 50% 40% 50% 40% 20% 30% 30% 20% 0%
Ike Walton 8 50% 25% 25% 38% 25% 25% 13% 13% 0%
White Sand 34 47% 38% 16% 21% 6% 3% 9% 0% 0%
Little Crawling Stone 10 60% 60% 70% 40% 20% 20% 20% 10% 10%
Pokegama 13 69% 69% 46% 38% 38% 38% 31% 8% 0%
Bear River Totals 171 49% 44% 35% 27% 22% 18% 19% 5% 5%
7-14 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Table 7-5. Perceived vs Actual Presence of AIS in Lakes
% of Respondents Believing AIS is Present vs. AIS Actually Present, Yes (Y) or No (N)
Lake #
Respondents BMS EWM RS CMS FJ RC CLPW PL
Crawling Stone 33 18% N 9% N 9% Y 6% N 0% N 36% y 0% N 18% N
Little Trout 0 0% N 0% N 0% Y 0% N 0% N 0% y 0% N 0% N
Fence 43 16% N 16% N 19% Y 7% N 0% N 30% N 2% N 5% y
Long Interlaken 10 20% N 20% N 0% Y 10% N 0% N 0% N 0% N 0% N
Flambeau 10 30% N 10% N 10% Y 20% N 10% N 20% N 0% N 10% y
Moss 10 30% N 20% N 0% N 10% N 30% N 10% N 30% N 60% Y
Ike Walton 8 13% N 0% N 0% N 0% N 0% N 13% N 0% N 0% N
White Sand 34 6% N 9% N 0% N 6% N 3% y 15% y 3% N 21% y
Little Crawling Stone 10 10% N 20% N 0% Y 0% Y 0% N 50% y 0% N 20% N
Pokegama 13 15% N 15% N 15% Y 0% Y 8% N 23% y 23% N 15% N
Bear River Totals 171 16% 13% 8% 6% 4% 25% 5% 15%
BMS: Banded mystery snail CLPW: Curly-leaf Pondweed EWM: Eurasian Water Milfoil RS: Rainbow Smelt CMS: Chinese mystery snail FJ: Freshwater Jellyfish PL: Purple Loosestrife RC: Rusty Crayfish
Table 7-6. Percent of Residents Looking for AIS and Frequency
Lake #
Respondents Never Once per Season Monthly Weekly Daily
Crawling Stone 31 38.70% 29% 9.70% 9.70% 12.90%
Little Trout 0 0% 0% 0% 0% 0%
Fence 41 43.90% 29.30% 19.5 2.40% 4.90%
Long Interlaken 9 55.60% 22.20% 22.2 0% 0%
Flambeau 10 40% 30% 0% 10% 20%
Moss 10 10% 30% 50% 10% 0%
Ike Walton 7 57.10% 28.60% 14.30% 0% 0%
White Sand 32 37.50% 34.40% 21.90% 6.20% 0%
Little Crawling Stone 9 33.30% 11.10% 22.20% 33.30% 0%
Pokegama 12 58.30% 16.70% 16.70% 8.30% 0%
Bear River Totals 161 41% 28% 18.60% 7.50% 5%
Section 7: About Aquatic Invasive Species 7-15
Bear River Watershed Comprehensive Lake Management Plan
Table 7-7. Residents Responding They Are Concerned About AIS
Lake # Respondents Extremely Concerned Somewhat Concerned Not Too Concerned Not Sure
Crawling Stone 33 36.40% 51.50% 3% 9%
Little Trout 0 0% 0% 0% 0%
Fence 42 52.40% 33.30% 4.80% 9.50%
Long Interlaken 9 33.30% 55.60% 11.10% 0%
Flambeau 9 33.30% 55.60% 11.10% 0%
Moss 10 20% 80% 0% 0%
Ike Walton 8 50% 25% 12.50% 12.50%
White Sand 34 58.80% 32.40% 2.90% 5.90%
Little Crawling Stone 9 100% 0% 0% 0%
Pokegama 13 46.20% 46.20% 0% 7.70%
Total Bear River 167 48.50% 40.70% 4.20% 6.60%
7-16 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Notes for Section 7 1. Wayne Grady The Great Lakes: The Natural History of a
Changing Region (Greystone Press, 2007) 274.
2. Scott Gatzke is the writer and performer of the folk song called The Ballad of Aquatic Invasive Species. This song and other songs by different writers and performers, such as One Boat, One Lake and Clean Boats, Clean Waters, are available (and can be listened to ) through the University of Wisconsin Extension: http://www.uwex.edu/erc/music/song_ballad_of_aquatic.html.
3. Wisconsin Department of Natural Resources online: http://dnr.wi.gov/topic/Invasives/what.html.
4. Ibid.
5. Ibid. Also see A Statewide Strategic Plan for Invasive Species: Priority Objectives 2013-2016 (Wisconsin Department of Natural Resources, April 2, 2013) 6. Online at http://invasivespecies.wi.gov/docview.asp?docid=24479. Also see Aquatic Invasive Species Monitoring Procedures (Wisconsin Department of Natural Resources, UW-Extension and Wisconsin Association of Lakes, prepared by Laura Herman, March 2009) 3. This document is a guide for citizens interested in monitoring for aquatic invasive species. The manual provides much information on the impacts of AIS. Online at http://www4.uwsp.edu/cnr/uwexlakes/CLMN/publications.asp
6. For specific information on the costs, see Estimating the Cost of Invasive Species in Northern Highland Lakes, a study that revealed an annual welfare loss of approximately $1800 on average per shoreline property as determined by survey of 2,955 residents in 2008. The research is available at http://lter.limnology.wisc.edu/research/research_highlight/estimating-costs. Also, the costs associated with Aquatic Invasive Species are of national concern. For a review of the economic impacts of AIS nationwide, see Sabrina J. Lovell, Susan F. Stone, and Linda Fernandez, The Economic Impacts of Aquatic Invasive Species: A Review of the Literature (Northeastern Agricultural and Resource Economics Association, Agriculture & Economics Resource Review, 2006)195-208. And, the problems and issues related to Aquatic Invasive Species are not limited to the United States and Wisconsin. For an interesting perspective on AIS and globalization, see Reuben P. Keller, Invasive Species in Europe: Ecology, Status, and Policy (Environmental Science in Europe, a SpringerOpen Journal, 2011), online at http://www.enveurope.com/content/23/1/23.
7. Information provided in periodic updates from the Vilas County Invasive Species Coordinator.
8. Climate Change Adaptation Plan - Draft (Office of Water, United States Environmental Protection Agency, September 2013) 4. Online at: http://epa.gov/climatechange/Downloads/impacts-adaptation/office-of-water-plan.pdf. Also see Global Climate Change Impacts in the United States; U.S. Global Change Research Program (Cambridge University Press, 2009) 122. Online at: http://downloads.globalchange.gov/usimpacts/pdfs/climate-impacts-report.pdf.
9. Aquatic Invasive Species Monitoring Procedures, 155.
10. Ibid.
11. Ibid.
12. U.S. Geological Survey online: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1045 (4/4/2013, Page 3).
13. U.S. Geological Survey online: (4/4/2013, page 3). http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1047
14. Aquatic Invasive Species Monitoring Procedures, 155.
15. Ibid.
16. U.S. Geological Survey online: http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1045. (4/4/2013, Page 3).
17. Aquatic Invasive Species Monitoring Procedures, 156.
18. As recently as November 11, 2013, Chinese mystery snails were available for purchase at $3.00 through Aquatic Community at: http://www.aquaticcommunity.com/ads/search.php?searchid=14409.
19. Aquatic Invasive Species Monitoring Procedures, 47.
20. Ibid.
21. Ibid.
22. Ibid.
23. Ibid.
24. Ibid.
25. Ibid, 48.
26. Ibid.
27. Ibid.
28. Ibid.
29. Ibid, 17.
30. Ibid.
31. Ibid.
32. Ibid.
33. Ibid.
34. Ibid.
35. Ibid.
36. Ibid, 18.
37. Ibid.
38. Ibid.
39. Ibid, 191.
40. Ibid.
41. Ibid.
42. Ibid.
43. Ibid.
44. Ibid.
45. Ibid, 192
46. Ibid.
47. Ibid.
48. Ibid.
49. Ibid.
50. Ibid, 105.
51. Ibid.
52. Ibid.
53. Ibid.
54. Ibid.
55. Ibid.
56. Ibid.
57. Ibid.
58. Wisconsin Department of Natural Resources. Online at: http://dnr.wi.gov/lakes/invasives/aisdetail.aspx?roiseq=22554562.
Section 7: About Aquatic Invasive Species 7-17
Bear River Watershed Comprehensive Lake Management Plan
59. History of Smelt in the Great Lakes (University of Wisconsin Sea Grant Institute). Online at: http://www.seagrant.wisc.edu/Home/Topics/FishandFisheries/Details.aspx?PostID=360.
60. Ibid.
61. Wisconsin Department of Natural Resources. Online at: http://dnr.wi.gov/topic/invasives/documents/classification/lr_osmerus_mordax.pdf.
62. Combination of information from multiple sources, including: see footnotes 59 and 61; and, USGS at: http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=796; and http://limnology.wisc.edu/personnel/jakevz/ais/rainbowsm
elt.html. 63. Wisconsin Department of Natural Resources, see
footnote 61.
64. Larry Wawronowicz, Director of Tribal Natural Resources Department. From a presentation made at a Lake Steward Workshop, August 4, 2010.
65. Wisconsin Department of Natural Resources, see footnote 61.
66. Aquatic Invasive Species Monitoring Procedures ,173.
67. Ibid.
68. Ibid.
69. Ibid.
70. Ibid.
71. Ibid.
72. Ibid.
73. Ibid.
74. Ibid.
75. Ibid, 174.
76. Ibid.
77. Reed Canary Grass Management Guide (Wisconsin Department of Natural Resources, PUB-FR-428 2000). Online at: at http://dnr.wi.gov/topic/forestmanagement/documents/pub/fr-428.pdf.
78. Through the Looking Glass, A Field Guide to Aquatic Plants (Reindl Printing, Inc., Merrill, WI., 2001) 48-49.
79. Reed Canary Grass Management Guide.
80. Ibid.
81. Ibid.
82. Fact sheet about the Yellow Iris provided by the Vilas County Land & Water Conservation Department, March 2013.
83. Wisconsin Department of Natural Resources. Online at: http://dnr.wi.gov/topic/invasives/fact/yellowflagiris.html.
84. Fact sheet about yellow iris, see footnote 82.
85. Ibid.
86. Wisconsin Department of Natural Resources, see footnote 83.
87. Fact sheet about yellow iris, see footnote 83.
88. Bear River Watershed Comprehensive Lake Management Plan Survey, Lake-by-lake Comparisons, 2012, See Appendix.
89. Ibid, Items 1, 2. See Appendix.
Figure Notes for Section 7 Figure 7-1. Chinese Mystery Snail. Photo from “Kemongsa Science In Picture” Volume 21, published by Kemongsa, 1993. http://www.in.gov/dnr/files/CHINESE_MYSTERY_S NAIL.pdf
Figure 7-2. Banded Mystery Snail. Amy Bensn, USGS. http://nas.er.usgs.gov/queries/factsheet.aspx?Speci esID=1047
Figure 7-3. Curly-Leaf Pondweed. Leslie J. Mehrhoff, University of Connecticut, http://www.mtweed.org/curlyleaf-pondweed/.
Figure 7-4. Infestation of Curly-Leaf Pondweed. Photo provided by Vilas County Invasive Species Coordinator. Raking curly-leaf pondweed from Little Saint Germain Lake in 2002.
Figure 7-5. Infestation of Curly-Leaf Pondweed. Little Saint Germain Lake, 2002. Photo provided by Vilas County Invasive Species Coordinator.
Figure 7-6. Turion of Curly-Leaf Pondweed. Robert W. Freckmann, Herbarium, University of Wisconsin, Stevens Point, http://www.mtweed.org/curlyleaf- pondweed/.
Figure 7-7. Comparison of EWM with the Native Northern Water Milfoil, Wisconsin Department of Natural Resources Wild Cards
Figure 7-8. Infestation of Eurasian Water Milfoil. Photo provided by Vilas County Invasive Species Coordinator.
Figure 7-9. Eurasian Water Milfoil Fragmention. EWM on Little Saint Germain Lake, 2002. Photo provided by Vilas County Invasive Species Coordinator.
Figure 7-10. Freshwater Jellyfish. Photo Open Cage Wikimedia Commons, http://newswatch.nationalgeographic.com/2012/08/3 1/freshwater-jellyfish-species-of-the-week/
Figure 7-11. Freshwater Jellyfish. Myriah Richerson, USGS/NAS, http://nas.er.usgs.gov/queries/FactSheet.aspx?speci esID=1068
Figure 7-12. Rusty Crayfish. Wisconsin Department of Natural Resources. http://dnr.wi.gov/org/caer/ce/eek/critter/invert/rustycr ayfish.htm
Figure 7-13. Rainbow Smelt, http://en.wikipedia.org/wiki/Rainbow_smelt
Figure 7-14. Rainbow Smelt, http://www.adirondackalmanack.com/2011/03/adiron dack-fish-rainbow-smelt.html
Figure 7-15. Spiny and Fishhook Waterfleas, Sea Grant Minnesota http://www.seagrant.umn.edu/ais/waterflea
Figure 7-16. Spiny Waterfleas on fishing line. Sea Grant Minnesota http://www.seagrant.umn.edu/ais/waterflea
Figure 7-17. Infestation of Reed Canary Grass. Minnesota Department of Natural Resources, Photo by Angela Anderson. http://www.dnr.state.mn.us/invasives/terrestrialplant s/grasses/reedcanarygrass.html
Figure 7-18. Yellow Flag Iris. Noxious Weed Control Board. http://www.nwcb.wa.gov/detail.asp?weed=78
7-18 Section 7: About Aquatic Invasive Species
Bear River Watershed Comprehensive Lake Management Plan
Figure 7-19. Purple Loosestrife. Maryland Department of Natural Resources, Photo by K.L. Kyde. http://dnr.maryland.gov/wildlife/Plants_Wildlife/Purpl eLoosestrife/index.asp
Table Notes for Section 7 Table 7-1. Presence of AIS Near or In Lac du Flambeau.
Table 7-2. Aquatic Invasive Species in Lac du Flambeau.
Table 7-3. Prior Knowledge of AIS. Data from Bear River Watershed Comprehensive Lake Management Plan Survey, Lake-by-lake Comparisons, June 2012, Question #25. See Appendix.
Table 7-4. Lake resident Survey on Lakes Perceived to be Threatened by AIS. Data from Bear River Comprehensive Lake Management Plan Survey, Lake-by-lake Comparisons, June 2012, Question #27. See Appendix.
Table 7-5. Perceived vs Actual Presence of AIS in Lakes. Bear River Watershed Comprehensive Lake Management Plan Survey, Lake-by-lake Comparisons, June 2012, Question #26. See Appendix.
Table 7-6. Percent of Residents Looking for AIS and Frequency. Bear River Watershed Comprehensive Lake Management Plan Survey, Lake-by-lake Comparisons, Question #28. See Appendix.
Table 7-7. Residents Responding They Are Concerned About AIS. Bear River Watershed Comprehensive Lake Management Plan Survey, Lake-by-Lake Comparisons, Question #29. See Appendix.
Figures Figure 7-1. Chinese Mystery Snail .................................... 7-3
Figure 7-2. Banded Mystery Snail ..................................... 7-3
Figure 7-3. Curly-Leaf Pondweed ..................................... 7-4
Figure 7-4. Infestation of Curly-Leaf Pondweed ................ 7-4
Figure 7-5. Infestation of Curly-Leaf Pondweed ................ 7-4
Figure 7-6. Turion of Curly-Leaf Pondweed ...................... 7-5
Figure 7-7. Comparison of EWM with the Native Northern Water Milfoil ............................................ 7-5
Figure 7-8. Infestation of Eurasian Water Milfoil ................ 7-6
Figure 7-9. Eurasian Water Milfoil Fragmentation ............. 7-6
Figure 7-10. Freshwater Jellyfish ...................................... 7-6
Figure 7-11. Freshwater Jellyfish ...................................... 7-7
Figure 7-12. Rusty Crayfish .............................................. 7-8
Figure 7-13. Rainbow Smelt .............................................. 7-8
Figure 7-14. Rainbow Smelt .............................................. 7-9
Figure 7-15. Spiny and Fishhook Waterfleas .................. 7-10
Figure 7-16. Spiny Waterfleas on Fishing Line ................ 7-10
Figure 7-17. Infestation of Reed Canary Grass ............... 7-11
Figure 7-18. Yellow Flag Iris ........................................... 7-11
Figure 7-19. Purple Loosestrife ....................................... 7-12
Tables Table 7-1. Presence of AIS Near or in Lac du
Flambeau* ............................................................. 7-1
Table 7-2. Aquatic Invasive Species in Lac du Flambeau Lakes* ................................................... 7-2
Table 7-3. Prior Knowledge of AIS .................................. 7-12
Table 7-4. Lake Resident Survey on Lakes Perceived to be Threatened by AIS ...................................... 7-13
Table 7-5. Perceived vs Actual Presence of AIS in Lakes ................................................................... 7-14
Table 7-6. Percent of Residents Looking for AIS and Frequency ............................................................ 7-14
Table 7-7. Residents Responding They Are Concerned About AIS ............................................................. 7-15
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