What are fungi?Associate Professor
Key Factors: Overfishing
Peak harvests in late 1800’s were nearly 150 million pounds; only 63 million today
Lack of management, improved fishing gear, other stressors
Key species: lake trout, sturgeon, Atlantic salmon, blue pike, whitefish, walleye, yellow perch
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Drainage of wetlands: loss of nursery habitat
Dams: block migration routes
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Fertilizers
Detergents
Canada and US: Great Lakes Water Quality Agreement in 1972
Phosphorus reductions very successful
Key Factors: Toxic Pollutants
Increased use of synthetic organic chemicals since 1940’s – persistent in the environment
Dangers first evident with pesticide DDT
Increased risk of cancer, birth defects, genetic mutation
Fish consumption advisories
Notable invaders: sea lamprey, carp, smelt, alewives, Pacific salmon, round gobies, zebra mussels
Significant effects possible
Displace native species
Current fish communities are very different from historical communities!
Native top predators such as Atlantic salmon and Lake trout replaced by introduced Pacific salmon
Supported by hatcheries and stocking
Native prey species such as lake herring and bloaters replaced by exotic rainbow smelt and alewife
Lake trout
Lake herring
Current Commercial Fisheries in the Great Lakes
Commercial fishing has declined significantly since its peak in the 1940’s and 1950’s
Important current species include
Commercial fishing limited by toxic contaminants and pressure from recreational fishing interests
Walleye
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Current Recreational Fisheries in the Great Lakes
Recreational or sport fishing has become very valuable in the Great Lakes region
Important species include
Walleye
The Alewife and Pacific Salmon
Two exotic species in the Great Lakes that have had huge impacts
Pacific salmon (coho and chinook) introduced in Lake Michigan in 1960’s to control alewives
World-class pacific salmon fishery developed, but
Relies on continued stocking of salmon
Contaminants in salmon
Obstacle to restoration of native species?
Alewife
Small fish: 4 - 10 in. with fused pelvic fin
Native to Europe
Has spread rapidly, very aggressive and tolerant
Competes with native species (especially sculpins), may eat fish eggs
Good bait for bass, may have contributed to spread!
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Native to Atlantic Ocean and Lake Ontario
Spread throughout Great Lakes via canals by 1947 – major declines in Lake trout
One adult lamprey consumes 20-30 lbs of fish in its lifetime
Sea lamprey populations reduced by 90% by control programs – expensive!
Most destructive invasive species in Great Lakes history
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Overall health of fish communities slowly improving over time
Habitat protection and restoration
Restoration of native species (Lake trout, Atlantic salmon, Lake sturgeon)
Challenges remain
for current and future generations!
Lake Sturgeon