Which of the following are “exotic species”?
Wheat in Kansas
Steelhead trout in Lake Michigan
Bluegrass in Kentucky
Zebra mussels in Lake Erie
Steps to become an invasive species…..
Disperse from native range to somewhere else
Survive in new habitat
Reproduce in new habitat
Naturalize (establish permanent population)
Become a problem (immigrant vs invasive spp)
lag phase when not
know if spp will
become invasive
Some conditions can promote invasiveness
Vacant “niches”: ecosystems with few species
Escape from predators and competators
Disturbance of ecosystem
Consequences of invasion: Great
Lakes case study
Great Lakes Introductions increase over time
Ricciardi et al 2001
Routes of introduction
 Canals
 (sea lamprey)
 alewife
 Ballast water importation
 zebra mussels
 spiny water flea
 goby
 ruffe
 Aquaculture and aquarium trade and intentional release
 carp
The Sea Lamprey
(Petromyzon marinus)
Primative (jawless) fish
Native to Atlantic Ocean
Adults predatory on large fish
 Probably entered Great Lakes via the Hudson River and
its artificial extension, the Erie Canal (opened to Lake
Ontario in 1819)
Erie Canal
Hudson
 Gained access to Lake Erie through Welland Canal
around Niagara Falls (completed 1829), but not
noted in Lake Erie until 1921
 Thereafter invasion quickened; found in Lake
Huron in 1932, Lake Michigan in 1936, and Lake
Superior in 1946.
 Lampreys devastated
http://www.glfc.org/slft.htm
lake trout populations in
Great Lakes
 Removal of top predator
allowed smaller fish such
as alewife (also introduced
through canals) to boom
 Lamprey control (pesticide applied to juvenile form in
streams)- continues today
 Coho & Chinook salmon easier to grow in hatcheries
than lake trout. These exotic species were heavily
stocked
Alewife
 Euryhaline species
 Traveled through canals
(maybe native to Ontario)
 Population expanded when lake trout died
 Efficient zooplankton eater, changed zooplankton and
contribute to decline of native fish (e.g. bloater)
Lake Trout
Pacific Salmon
Bloater
Whitefish
Sea Lamprey
Alewife
Large zooplankton
Small zooplankton
Phytoplankton
Ballast-mediated species Introduction
discharge
uptake
transport
Water is used for ballast, but sediments accumulate too
Can contain resting stages or live animals
Dreissenid Mussels
History
 Ponto-Caspian origin
 Ballast transport
 First found in Lake St. Clair
http://www.earthwave.org/zmussel.htm
Biology
 Adults attach to substrate
 Planktonic larvae
 High population density
 High filtration rate
Zebra mussel covering hard substrate and
spreading over soft sediment in Oneida Lake, NY
Total coverage of
sediments in St
Lawrence Seaway
Covering hard objects
 Increase in water clarity in Oneida Lake, NY
5
Secchi depth (m)
zebra
mussels
4
3
2
1975
1980
1985
1990
1995
2000
Bay of Quinte; S. Millard, DFO
Lake Erken; P. Eklov, Uppsala U.
Western Lake Erie; S. Ludsin
Onieda Lake; CBFS
Naroch Lakes chain; L. Brulakova & A.
Karatayev, Austin St. U.
Mean annual Secchi depth (m)
pre zebra mussel
post zebra mussel
pre zebra mussel
6
80
70
5
60
4
50
40
3
30
2
20
1
10
0
0
Naroch
Oneida
Erie
Erken
Quinte N
Lake
Quinte B
Myastro
Batorino
Mean pre-zebra mussel TP (ug/L)
90
7
Dreissena and Unionid Clams
Some species extremely long lived, > 100 years
Do not mature for relatively long time ~> 10 years
Populations already hurt by water quality
problems and dams
 Zebra mussels
encrust unionid
shells. Interference
competition
 Native clams
usually disappear w/
in 5 yr of zebra
mussel introduction
Bythotrephes
 A native of Great Britain and northern
Europe
 Discovered in Lake Huron in 1984
 Spread to all the Great Lakes and some
http://www.miseagrant.org/ans/zoo.html
inland lakes.
Native Daphnia spp.
short vs. long spine
big vs. small body
http://ebiomedia.com/gall/classics/Daphnia/feature_main.html
Which would fish rather eat??
http://www.miseagrant.org/ans/zoo.html
http://ebiomedia.com/gall/classics/Daphnia/feature_main.html
 Feeds on smaller zooplankton in the Great Lakes
 May be reducing food for native plankton and fish
species
Round Goby
http://www.miseagrant.org/ans/fish.html
 Eat zebra mussels
 May compete with native darters or sculpins
 May consume eggs of natives (lake trout)
Eurasian Ruffe
European perch family
discovered in Duluth harbor
in 1985.
http://www.miseagrant.org/ans/fish.html
Have spread around Lakes Superior and have established a
population in Thunder Bay near Alpena, Michigan.
In some areas, explosive population growth and displace native
species such as y.p. and emerald shiners
Sharp spines make them difficult for larger fish to eat
Aquaculture Releases
Carp
European settlers
for food and fishing
well established population
Asian Carp
Southern fish farms
Knocking on the door: Asian carp
 several species, accidentally
released from aquaculture
facility.
 ~ 40 mi from Lake Michigan.
 Electrical barrier in place in
Chicago.
http://www.glfc.org/fishmgmt/carp.asp
Economics of electrical barrier
Construction cost?
Maintenance cost?
Will it work?
MN proposing bubble and sound curtain
57% effective
Lake Trout
Pacific Salmon
Bloater
Whitefish
Sea Lamprey
Alewife
goby
Spiny flea
Large zooplankton
Small zooplankton
Asian carp
Benthic algae
Zebra mussels
Phytoplankton
Invasional Meltdown
Theory that suggests that current invasions may
facilitate future invasions
Exotics don’t necessarily compete with one
another, may make it easier for others to get in.
Compare to “biotic resistance” or “empty niche”
theories described in reading
Prevention and Control
Prevent entry:
International trade treaties
International and interstate commerce
Examples: Garden plants, pets, aquarium fish,
agricultural species
Shipping industry regulations
Examples: all GL species
Very difficult to predict which species will become
invasive
How to decide which species cannot be imported
Eradication
Possible if detected early
Biology of species important, ex. it has slow
dispersal or depends on few other spp. for
survival
Long-term effort: funding for eradication program
is not cut
Public support
Maintenance Control
Keep population at low level to avoid ecological
damage
Some successful examples