Zebra mussel (Dreissena polymorpha)
how it got here: similar to the goby, the zebra mussel
is also native to the black sea, and was brought over in
ballast water in the late 1980s. It’s a small, prolific mussel
about the size of your pinky nail, with a distinctive zebra
stripe shell pattern and a razor-sharp edge.
the bad: Zebra mussels are notorious for explosive
growth that damages and fouls industrial equipment
such as intake and exhaust pipes, navigational buoys,
docks, and pilings. they also have profound ecosystem
impacts, like severely decreased phytoplankton biomass,
reduced populations of some fish species from nutrient-
poor water, and increased bio-availability of pollutants
such as pCbs and mercury.
the good: In short, they clear up the water. Zebra
mussels have spread through much of the eastern part of
the country, and many infested lakes feature much clear-
er and cleaner water after their introduction, which can
enhance fisheries for some species of game fish and
improve aesthetics for recreational and pleasure boaters.
summer 2019 I FlWFIshInG.com
Water hyacinth (Eichhornia crassipes)
how it got here: Native to south America, the water
hyacinth was introduced to the u.s. in the 1800s by orna-
mental gardeners, as it’s a very attractive free-floating
plant with beautiful purple flowers. It’s a popular aquari-
um plant and is sold in many greenhouses.
the bad: Water hyacinth grows in vast, dense mats on
the surface, which decrease light penetration and reduce
both animal and plant diversity. hyacinth mats also
decrease dissolved oxygen and alter nutrient and turbidity
conditions. they can create physical problems by clogging
up docks, marinas, dams and other navigational structures.
the good: hyacinth mats create overhead cover, which
can (in moderation) increase available cover for young-of-
the-year fish, as well as game fish and panfish species.
how it got here: A small, bottom-dwelling fish native
to the black and Caspian seas, the round goby is believed
to have been transported to the Great Lakes in the 1980s
in the ballast water of freighters coming from Europe.
First recorded in 1990, the Round Goby has quickly
spread throughout the Great Lakes watershed as well as
many inland lakes across the upper Midwest.
the bad: Gobies are extremely aggressive, and studies
have shown native fish diversity is severely decreased in
areas where round gobies are abundant. they have also
been shown to negatively impact nest success of small-
mouth bass and other native fish species.
the good: Gobies are an extremely abundant and
nutritious food source for many predatory populations,
including bass, walleyes, and even non-fishes such as the
Lake Erie water snake and double crested cormorant. the
abundance of gobies has improved growth rates (length-
at-age) of predatory fish species, as well as improved the
recreational fishery for many anglers.
round Goby (Neogobius melanostomus)
northern snakehead (Channa argus)
how it got here: Native to China, Russia and Korea, the
northern snakehead was introduced to u.s. waters in the late
1990s by illegal release from aquariums and live food mar-
kets. In the early 2000s, there was a memorable “frankenfish”
frenzy, as various media outlets reported frightening stories
of the projected spread of the voracious feeder.
the bad: Northern snakeheads compete with native
populations for food and habitat. studies have shown that
their diets significantly overlap with the largemouth bass in
most areas of their establishment, and the fish can lead to
reduced abundance of many native species such as bowfin.
the good: Northern snakehead have created thriving
niche fisheries in many waters in which they have estab-
lished themselves. they are extremely aggressive, hard
fighters and willingly attack many of the same lures you’d
use bass fishing. they are also considered excellent table
fare. Many anglers are starting to target them specifically
as a food fish.
tJ Maglio is a tournament angler and outdoor writer based in
Minnesota. he has a degree in wildlife ecology from the university of
Wisconsin, Madison and has also worked professionally as a wildlife
biologist and environmental consultant.
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