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The Disrupted

Food Web of the

Great Lakes

By Jason Treat, Kelsey Nowakowski,

and Eve Conant

Illustrations By Fiorella Ikeue

A thriving, complex food web is crucial to the health of one of Earth’s largest surface freshwater ecosystems. But introductions and invasions of non-native aquatic plants and animals, the harvesting and stocking of top predator fish, and elevated nutrient and contaminant levels have snarled the Great Lakes food web, affecting fisheries, wildlife, and the health of the ecosystem.

Number of new invasive species in the Great Lakes

by year

early 1800s

The original alpha

Lake trout were once at the top of the Great Lakes food chain. Their numbers were decimated during the past century after the introduction of the non-native sea lamprey.

Invasive

Stocked/managed

1860

1870

Alewives discovered in Lake Ontario

1880

Brown trout introduced in Lake Michigan

1890

Common carp

1930s

Sea lampreys disrupt the food chain

Sea lampreys invaded via locks and canals; they attach to large fish and suck their blood. Lake trout, whitefish, and chub populations began collapsing by the 1940s and 1950s.

1900

1910

Rainbow smelt

1920

1930

Sea lamprey discovered in Lake Michigan

mid-1960s

Invasive alewife populations expand

Without lake trout to feed on the alewife—a small river herring—the invasive fish’s population exploded throughout the lakes.

1940

White perch

1950

1960

late 1960s

Sport fish are introduced to manage invasive species

Introduced Pacific salmon consume alewife and rainbow smelt and provide a sport fishery that’s heavily managed through stocking and harvest regulations.

Salmon

1970

1980

Ruffe

Zebra mussels

Quagga mussels

1990

Zebra mussels

2000

Quagga mussels

1980s

Invasive mussels destroy the

base of the web

Invasive zebra mussels were surpassed by the closely related quagga mussels. Both carpet the lake bed, relentlessly filtering vital phyto­plankton from the water.

2010

2019

The lakes today

More than 180 invasive species with

reproducing populations continue to

threaten the Great Lakes Basin.

Key

Michigan

Superior

Ontario

Huron

Erie

Species dominant in lake

Parasite

Parasites live on or in a host species and feed at the expense of the host. The most widespread in the lakes are sea lampreys, which attach to large fish and suck their blood. Some fish populations have collapsed as a result.

Invasive species

Sea lamprey

Petromyzon marinus

Eats fish eaters

Eats forage fish

Species from the lower levels of the food web

are prey for the sea lamprey

Fish Eaters

Fish eaters are the top of the food web and support a valuable fishery. Some non-native fish eaters such as salmon were deliberately introduced to eat non-native forage fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Native species

Stocked/managed

Lake trout

Salvelinus namaycush

Eats forage fish

Coho salmon

Oncorhynchus kisutch

Eats forage fish

Chinook salmon

Oncorhynchus tshawytscha

Eats forage fish

Burbot

Lota lota

Eats forage fish

Eats macroinvertebrates

Walleye

Stizostedion vitreum

Eats forage fish

Eats macroinvertebrates

Brown trout

Salmo trutta

Eats forage fish

Rainbow trout

Oncorhynchus mykiss

Eats forage fish

Smallmouth bass

Micropterus dolomieu

Eats forage fish

Eats macroinvertebrates

White bass

Morone chrysops

Eats forage fish

Introduced rainbow trout have long been stocked and managed to provide a sport fishery in near-shore areas and in connected tributaries.

Atlantic salmon

Salmo salar

Eats forage fish

American eel

Anguilla rostrata

Eats forage fish

Brook trout

Salvelinus fontinalis

Eats forage fish

Forage Fish

Forage fish—an important link between the lower and upper food web— consume macroinvertebrates, zooplankton, and larval fish, and in turn are eaten by larger fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Native species

Lake sturgeon

Acipenser fulvescens

Eats round gobies

Eats macroinvertebrates

Lake sturgeons are large, ancient fish that eat organisms on the lake bottom, including invasive mussels and round gobies.

Kiyi

Coregonus kiyi

Eats macroinvertebrates

Eats zooplankton

Invasive species

Cisco

Coregonus artedi

Eats macroinvertebrates

Eats zooplankton

Ruffe

Gymnocephalus cernuus

Eats macroinvertebrates

Eats zooplankton

Chubs and ciscoes eat zooplankton, small crustaceans, and fish, and are prey for piscivores.

Rainbow smelt

Osmerus mordax

Eats macroinvertebrates

Eats zooplankton

Bloater

Coregonus hoyi

Eats macroinvertebrates

Eats zooplankton

Rainbow smelts feed on zooplankton and larval fish, including their own young. They’re eaten by game fish and harvested by fisheries.

Emerald shiner

Notropis atherinoides

Eats macroinvertebrates

Eats zooplankton

Alewife

Alosa pseudoharengus

Eats macroinvertebrates

Eats zooplankton

Deepwater sculpin

Myoxocephalus

thompsonii

Eats macroinvertebrates

Common carp

Cyprinus carpio

Eats macroinvertebrates

Eats zooplankton

Slimy sculpin

Cottus cognatus

Eats macroinvertebrates

Yellow perch

Perca flavescens

Eats macroinvertebrates

Eats zooplankton

White perch

Morone americana

Eats macroinvertebrates

Eats zooplankton

Channel catfish

Ictalurus punctatus

Eats macroinvertebrates

Freshwater drum

Aplodinotus grunniens

Eats macroinvertebrates

A hijacked system

Invasive species have rewired the Great Lakes food web. Sea lampreys attack top predators; round gobies compete with fish for food sources and habitat. Meanwhile, invasive mussels redirect the flow of energy, diverting food from the water column to the lake bed.

Round goby

Neogobius melanostomus

Eats macroinvertebrates

Eats zooplankton

Lake whitefish

Coregonus clupeaformis

Eats macroinvertebrates

Eats zooplankton

Native lake whitefish eat invasive mussels, which are low in nutritional value, producing declines in this important cultural and commercial fish.

Round gobies aggressively consume zebra and quagga mussels. They’re eaten by several fish and birds, carrying toxins up the food web.

Macroinvertebrates

Macroinvertebrates are a diverse and integral group of mostly bottom-dwelling organisms that can be seen with the naked eye. They consume other smaller invertebrates, plankton, and decaying material.

Macroinvertebrates eat groups below them

like zooplankton and phytoplankton

Native species

Invasive species

Opossum shrimp

Mysis relicta

Eats zooplankton

Eats phytoplankton

Zebra and quagga mussels

Dreissena polymorpha

and Dreissena bugensis

Eat phytoplankton

Chironomids/

Oligochaetes

Eat phytoplankton

Mollusks

Eat phytoplankton

New Zealand mud snail

Potamopyrgus

antipodarum

Eats phytoplankton

Mayfly nymphs

Hexagenia spp.

Eat phytoplankton

Bloody red shrimp

Hemimysis anomala

Eats zooplankton

Eats phytoplankton

Amphipods

Diporeia

Eat phytoplankton

Fishhook water flea

Cercopagis pengoi

Eats zooplankton

Eats phytoplankton

Amphipods

Gammarus

Eat zooplankton

Eat phytoplankton

Bythotrephes, a water flea with a long, spiny tail, eats other zooplankton and competes with fish for food. It’s now widespread in the lakes.

Spiny water flea

Bythotrephes longimanus

Eats zooplankton

ZOoplankton

Zooplankton are microscopic animals found mainly in the water column. They consume phytoplankton and are consumed by other animals, including predatory zooplankton and forage fish.

Phytoplankton

Microorganisms fuel the web. Phytoplankton—

including Cyclotella and other diatoms—are eaten by zooplankton and bottom-dwelling organisms. Cyanobacteria such as Microcystis are also key primary producers.

Microcystis

Cyclotella

Sources: Ashley Elgin, Doran Mason,

Ed Rutherford, and Rochelle Sturtevant, NOAA Great Lakes Environmental Research Laboratory

The disrupted

food web of

the great lakes

By Jason Treat, Kelsey Nowakowski, and Eve Conant

Illustrations By Fiorella Ikeue

PublisheD November 17, 2020

A thriving, complex food web is crucial to the health of one of Earth’s largest surface freshwater ecosystems. But introductions and invasions of non-native aquatic plants and animals, the harvesting and stocking of top predator fish, and elevated nutrient and contaminant levels have snarled the Great Lakes food web, affecting fisheries, wildlife, and the health of the ecosystem.

Number of new invasive species

in the Great Lakes by year

Invasive species

Stocked/managed species

Alewives

discovered

in Lake Ontario

Brown trout

introduced in

Lake Michigan

Sea lamprey

discovered

in Lake Michigan

Ruffe

Zebra mussels

Salmon

Quagga mussels

Common carp

Rainbow smelt

White perch

1910

1950

1870

1930

1970

1920

2019

1880

1960

1890

1980

1860

1990

1940

2010

1900

2000

early 1800s

The original alpha

Lake trout were once at the top of the Great Lakes food chain. Their numbers were decimated during the past century after the introduction of the non-native sea lamprey.

Lake trout

Salvelinus namaycush

1930s

Sea lampreys disrupt

the food chain

Sea lampreys invaded via locks and canals; they attach to large fish and suck their blood. Lake trout, whitefish, and chub populations began collapsing by the 1940s and 1950s.

Sea lamprey

Petromyzon marinus

mid-1960s

Invasive alewife

populations expand

Without lake trout to feed on the alewife—a small river herring—the invasive fish’s population exploded throughout the lakes.

Alewife

Alosa pseudoharengus

late 1960s

Sport fish are introduced

to manage invasive species

Introduced Pacific salmon consume alewife and rainbow smelt and provide a sport fishery that’s heavily managed through stocking and harvest regulations.

Chinook salmon

Oncorhynchus tshawytscha

Quagga mussels

Dreissena bugensis

1980s

Invasive mussels destroy

the base of the web

Invasive zebra mussels were surpassed by the closely related quagga mussels. Both carpet the lake bed, relentlessly filtering vital phyto­plankton from the water.

Zebra mussels

Dreissena polymorpha

The lakes today

More than 180 invasive species with reproducing populations continue to threaten the Great Lakes Basin.

Michigan

Superior

Ontario

Huron

Erie

Key

Species dominant in lake

Parasite

Parasites live on or in a host species and feed at the expense of the host. The most widespread in the lakes are sea lampreys, which attach to large fish and suck their blood. Some fish populations have collapsed as a result.

Sea lamprey

Petromyzon marinus

Eats fish eaters

Eats forage fish

Species from the lower levels of the food web

are prey for the sea lamprey

Fish Eaters

Fish eaters are the top of the food web and support a valuable fishery. Some non-native fish eaters such as salmon were deliberately introduced to eat non-native forage fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Native species

Stocked/managed

Lake trout

Salvelinus namaycush

Eats forage fish

Burbot

Lota lota

Eats forage fish

Eats macroinvertebrates

Chinook salmon

Oncorhynchus tshawytscha

Eats forage fish

Smallmouth bass

Micropterus dolomieu

Eats forage fish

Eats macroinvertebrates

Walleye

Stizostedion vitreum

Eats forage fish

Eats macroinvertebrates

Coho salmon

Oncorhynchus kisutch

Eats forage fish

White bass

Morone chrysops

Eats forage fish

Atlantic salmon

Salmo salar

Eats forage fish

Brown trout

Salmo trutta

Eats forage fish

Introduced rainbow trout have long been stocked and managed to provide a sport fishery in near-shore areas and in connected tributaries.

American eel

Anguilla rostrata

Eats forage fish

Brook trout

Salvelinus fontinalis

Eats forage fish

Rainbow trout

Oncorhynchus mykiss

Eats forage fish

Forage Fish

Forage fish—an important link between the lower and upper food web— consume macroinvertebrates, zooplankton, and larval fish, and in turn are eaten by larger fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Lake sturgeons are large, ancient fish that eat organisms on the lake bottom, including invasive mussels and round gobies.

Native species

Invasive species

Lake sturgeon

Acipenser fulvescens

Eats round gobies

Eats macroinvertebrates

Emerald shiner

Notropis atherinoides

Eats macroinvertebrates

Eats zooplankton

Alewife

Alosa pseudoharengus

Eats macroinvertebrates

Eats zooplankton

Ruffe

Gymnocephalus cernuus

Eats macroinvertebrates

Eats zooplankton

Slimy sculpin

Cottus cognatus

Eats macroinvertebrates

Deepwater sculpin

Myoxocephalus

thompsonii

Eats macroinvertebrates

Cisco

Coregonus artedi

Eats macroinvertebrates

Eats zooplankton

Common carp

Cyprinus carpio

Eats macroinvertebrates

Eats zooplankton

Bloater

Coregonus hoyi

Eats macroinvertebrates

Eats zooplankton

Rainbow smelt

Osmerus mordax

Eats macroinvertebrates

Eats zooplankton

Chubs and ciscoes eat zooplankton, small crustaceans, and fish, and are prey for piscivores.

Rainbow smelts feed on zooplankton and larval fish, including their own young. They’re eaten by game fish and harvested by fisheries.

Yellow perch

Perca flavescens

Eats macroinvertebrates

Eats zooplankton

Freshwater drum

Aplodinotus grunniens

Eats macroinvertebrates

White perch

Morone americana

Eats macroinvertebrates

Eats zooplankton

Kiyi

Coregonus kiyi

Eats macroinvertebrates

Eats zooplankton

Channel catfish

Ictalurus punctatus

Eats macroinvertebrates

Round goby

Neogobius melanostomus

Eats macroinvertebrates

Eats zooplankton

Lake whitefish

Coregonus clupeaformis

Eats macroinvertebrates

Eats zooplankton

A hijacked system

Invasive species have rewired the Great Lakes food web. Sea lampreys attack top predators; round gobies compete with fish for food sources and habitat. Meanwhile, invasive mussels redirect the flow of energy, diverting food from the water column to the lake bed.

Native lake whitefish eat invasive mussels, which are low in nutritional value, producing declines in this important cultural and commercial fish.

Round gobies aggressively consume zebra and quagga mussels. They’re eaten by several fish and birds, carrying toxins up the food web.

Macroinvertebrates

Macroinvertebrates are a diverse and integral group of mostly bottom-dwelling organisms that can be seen with the naked eye. They consume other smaller invertebrates, plankton, and decaying material.

Macroinvertebrates eat groups below them

like zooplankton and phytoplankton

Native species

Invasive species

Opossum shrimp

Mysis relicta

Eats zooplankton

Eats phytoplankton

Zebra and quagga mussels

Dreissena polymorpha

and Dreissena bugensis

Eat phytoplankton

Bloody red shrimp

Hemimysis anomala

Eats zooplankton

Eats phytoplankton

Chironomids/

Oligochaetes

Eat phytoplankton

Mayfly nymphs

Hexagenia spp.

Eat phytoplankton

Mollusks

Eat phytoplankton

New Zealand mud snail

Potamopyrgus

antipodarum

Eats phytoplankton

Fishhook water flea

Cercopagis pengoi

Eats zooplankton

Eats phytoplankton

Amphipods

Diporeia

Eat phytoplankton

Amphipods

Gammarus

Eat zooplankton

Eat phytoplankton

Spiny water flea

Bythotrephes longimanus

Eats zooplankton

Bythotrephes, a water flea with a long, spiny tail, eats other zooplankton and competes with fish for food. It’s now widespread in the lakes.

ZOoplankton

Zooplankton are microscopic animals found mainly in the water column. They consume phytoplankton and are consumed by other animals, including predatory zooplankton and forage fish.

Phytoplankton

Microorganisms fuel the web. Phytoplankton—including Cyclotella and other diatoms—are eaten by zooplankton and bottom-dwelling organisms. Cyanobacteria such as Microcystis are also key primary producers.

Cyclotella

Microcystis

Sources: Ashley Elgin, Doran Mason, Ed Rutherford, and Rochelle Sturtevant,

NOAA Great Lakes Environmental Research Laboratory

The disrupted food web

of the great lakes

By Jason Treat, Kelsey Nowakowski, and Eve Conant

Illustrations By Fiorella Ikeue

PublisheD November 17, 2020

A thriving, complex food web is crucial to the health of one of Earth’s largest surface freshwater ecosystems. But introductions and invasions of non-native aquatic plants and animals, the harvesting and stocking of top predator fish, and elevated nutrient and contaminant levels have snarled the Great Lakes food web, affecting fisheries, wildlife, and the health of the ecosystem.

Number of new invasive species

in the Great Lakes by year

Invasive species

Stocked/managed species

Zebra mussels

Quagga mussels

Alewives discovered

in Lake Ontario

Brown trout

introduced in

Lake Michigan

Ruffe

Sea lamprey discovered

in Lake Michigan

Salmon

Common carp

Rainbow smelt

White perch

1910

1950

1870

1930

1970

1920

2019

1880

1960

1890

1980

1860

1990

1940

2010

1900

2000

early 1800s

The original alpha

Lake trout were once at the top of the Great Lakes food chain. Their numbers were decimated during the past century after the introduction of the non-native sea lamprey.

Lake trout

Salvelinus namaycush

1930s

Sea lampreys disrupt

the food chain

Sea lampreys invaded via locks and canals; they attach to large fish and suck their blood. Lake trout, whitefish, and chub populations began collapsing by the 1940s and 1950s.

Sea lamprey

Petromyzon marinus

mid-1960s

Invasive alewife

populations expand

Without lake trout to feed on the alewife—a small river herring—the invasive fish’s population exploded throughout the lakes.

Alewife

Alosa pseudoharengus

late 1960s

Sport fish are introduced

to manage invasive species

Introduced Pacific salmon consume alewife and rainbow smelt and provide a sport fishery that’s heavily managed through stocking and harvest regulations.

Chinook salmon

Oncorhynchus tshawytscha

Quagga mussels

Dreissena bugensis

1980s

Invasive mussels destroy

the base of the web

Invasive zebra mussels were surpassed by the closely related quagga mussels. Both carpet the lake bed, relentlessly filtering vital phyto­plankton from the water.

Zebra mussels

Dreissena polymorpha

The lakes today

More than 180 invasive species with reproducing populations continue to threaten the Great Lakes Basin.

Michigan

Superior

Ontario

Huron

Erie

Key

Species dominant in lake

Parasite

Parasites live on or in a host species and feed at the expense of the host. The most widespread in the lakes are sea lampreys, which attach to large fish and suck their blood. Some fish populations have collapsed as a result.

Sea lamprey

Petromyzon marinus

Eats fish eaters

Eats forage fish

Species from the lower levels of the food web

are prey for the sea lamprey

Fish Eaters

Fish eaters are the top of the food web and support a valuable fishery. Some non-native fish eaters such as salmon were deliberately introduced to eat non-native forage fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Native species

Stocked/managed

Coho salmon

Oncorhynchus kisutch

Eats forage fish

Chinook salmon

Oncorhynchus tshawytscha

Eats forage fish

Lake trout

Salvelinus namaycush

Eats forage fish

Burbot

Lota lota

Eats forage fish

Eats macroinvertebrates

Walleye

Stizostedion vitreum

Eats forage fish

Eats macroinvertebrates

Brown trout

Salmo trutta

Eats forage fish

Atlantic salmon

Salmo salar

Eats forage fish

Introduced rainbow trout have long been stocked and managed to provide a sport fishery in near-shore areas and in connected tributaries.

Smallmouth bass

Micropterus dolomieu

Eats forage fish

Eats macroinvertebrates

White bass

Morone chrysops

Eats forage fish

Rainbow trout

Oncorhynchus mykiss

Eats forage fish

American eel

Anguilla rostrata

Eats forage fish

Brook trout

Salvelinus fontinalis

Eats forage fish

Forage Fish

Forage fish—an important link between the lower and upper food web— consume macroinvertebrates, zooplankton, and larval fish, and in turn are eaten by larger fish.

Fish eaters eat groups below them

like forage fish and macroinvertebrates

Lake sturgeons are large, ancient fish that eat organisms on the lake bottom, including invasive mussels and round gobies.

Native species

Invasive species

Bloater

Coregonus hoyi

Eats macroinvertebrates

Eats zooplankton

Alewife

Alosa pseudoharengus

Eats macroinvertebrates

Eats zooplankton

Emerald shiner

Notropis atherinoides

Eats macroinvertebrates

Eats zooplankton

Lake sturgeon

Acipenser fulvescens

Eats round gobies

Eats macroinvertebrates

Ruffe

Gymnocephalus cernuus

Eats macroinvertebrates

Eats zooplankton

Deepwater sculpin

Myoxocephalus

thompsonii

Eats macroinvertebrates

Slimy sculpin

Cottus cognatus

Eats macroinvertebrates

Common carp

Cyprinus carpio

Eats macroinvertebrates

Eats zooplankton

Cisco

Coregonus artedi

Eats macroinvertebrates

Eats zooplankton

Chubs and ciscoes eat zooplankton, small crustaceans, and fish, and are prey for piscivores.

Rainbow smelts feed on zooplankton and larval fish, including their own young. They’re eaten by game fish and harvested by fisheries.

Rainbow smelt

Osmerus mordax

Eats macroinvertebrates

Eats zooplankton

Yellow perch

Perca flavescens

Eats macroinvertebrates

Eats zooplankton

Freshwater drum

Aplodinotus grunniens

Eats macroinvertebrates

Kiyi

Coregonus kiyi

Eats macroinvertebrates

Eats zooplankton

White perch

Morone americana

Eats macroinvertebrates

Eats zooplankton

Channel catfish

Ictalurus punctatus

Eats macroinvertebrates

Round goby

Neogobius melanostomus

Eats macroinvertebrates

Eats zooplankton

Lake whitefish

Coregonus clupeaformis

Eats macroinvertebrates

Eats zooplankton

A hijacked system

Invasive species have rewired the Great Lakes food web. Sea lampreys attack top predators; round gobies compete with fish for food sources and habitat. Meanwhile, invasive mussels redirect the flow of energy, diverting food from the water column to the lake bed.

Native lake whitefish eat invasive mussels, which are low in nutritional value, producing declines in this important cultural and commercial fish.

Round gobies aggressively consume zebra and quagga mussels. They’re eaten by several fish and birds, carrying toxins up the food web.

Macroinvertebrates

Macroinvertebrates are a diverse and integral group of mostly bottom-dwelling organisms that can be seen with the naked eye. They consume other smaller invertebrates, plankton, and decaying material.

Macroinvertebrates eat groups below them

like zooplankton and phytoplankton

Native species

Invasive

Opossum shrimp

Mysis relicta

Eats zooplankton

Eats phytoplankton

Chironomids/

Oligochaetes

Eat phytoplankton

Zebra and quagga mussels

Dreissena polymorpha

and Dreissena bugensis

Eat phytoplankton

Bloody red shrimp

Hemimysis anomala

Eats zooplankton

Eats phytoplankton

Mayfly nymphs

Hexagenia spp.

Eat phytoplankton

Mollusks

Eat phytoplankton

New Zealand mud snail

Potamopyrgus

antipodarum

Eats phytoplankton

Fishhook water flea

Cercopagis pengoi

Eats zooplankton

Eats phytoplankton

Bythotrephes, a water flea with a long, spiny tail, eats other zooplankton and competes with fish for food. It’s now widespread in the lakes.

Amphipods

Diporeia

Eat phytoplankton

Amphipods

Gammarus

Eat zooplankton

Eat phytoplankton

Spiny water flea

Bythotrephes longimanus

Eats zooplankton

ZOoplankton

Zooplankton are microscopic animals found mainly in the water column. They consume phytoplankton and are consumed by other animals, including predatory zooplankton and forage fish.

Phytoplankton

Microorganisms fuel the web. Phytoplankton—including Cyclotella and other diatoms—are eaten by zooplankton and bottom-dwelling organisms. Cyanobacteria such as Microcystis are also key primary producers.

Cyclotella

Microcystis

Sources: Ashley Elgin, Doran Mason, Ed Rutherford, and Rochelle Sturtevant, NOAA Great Lakes Environmental Research Laboratory