Geology. Key Factors. Overfishing. Great Lakes Fishes. Historical Fishing. About 10,000 years since last glacial retreat very young ecologically

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1 Great Lakes Fishes Geology About 10,000 years since last glacial retreat very young ecologically Largest surface freshwater system on earth 21% of world s supply 84% of North America s supply Five unique lakes Key Factors Overfishing Habitat destruction Eutrophication Toxic pollutants Invasive species Overfishing Historical Fishing 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 1

2 Habitat Destruction European settlement and urbanization Deforestation: loss of cover, sedimentation, increased stream temperatures Drainage of wetlands: loss of nursery habitat Dams: block migration routes Loss of habitat greatly impacted Lake sturgeon in Lake Erie Atlantic salmon in Lake Ontario Eutrophication Cultural eutrophication: accelerated input of nutrients (esp. phosphates) into waterways, decreased dissolved oxygen Fertilizers Detergents Water treatment plants Lake Erie very susceptible Shallow and warm Extensive agricultural development in watershed Lake Erie is dead in the 1960 s Canada and US: Great Lakes Water Quality Agreement in 1972 Phosphorus reductions very successful Accelerated Eutrophication 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 Toxic Pollutants Bioaccumulation of PCB s 2

3 Invasive Species Great Lakes Invasive Species Canals (Welland, Erie) and ballast water Notable invaders: sea lamprey, carp, smelt, alewives, Pacific salmon, round gobies, zebra and quagga mussels Significant effects possible Displace native species Reduce biodiversity Alter established ecosystems Current Status of Great Lakes Fish Communities 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 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 Walleye Yellow perch Lake whitefish Rainbow smelt Alewife (for animal feed) Walleye Commercial fishing limited by toxic contaminants and pressure from recreational fishing interests Lake trout Lake herring Current Recreational Fisheries in the Great Lakes Recreational or sport fishing has become very valuable in the Great Lakes region Important species include Pacific salmon (coho and chinook) Walleye Yellow perch Largemouth and smallmouth bass Northern pike and muskie 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 Dependent upon an exotic species, the alewife Obstacle to restoration of native species? Muskie Smallmouth bass Chinook salmon Alewife Alewife die-off! Coho salmon 3

4 The Round Goby Our Newest Exotic Fish Invader Small fish: 4-10 in. with fused pelvic fin Native to Europe Ballast water introduction around 1990 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! The Future of Great Lakes Fisheries Overall health of fish communities slowly improving over time Habitat protection and restoration Reduction in pollutants Better management Restoration of native species (Lake trout, t Atlantic salmon, Lake sturgeon) Challenges remain Fish consumption advisories Exotic species Lake Sturgeon Great Lakes fishes are a valuable resource for current and future generations! Case Studies Important Great Lakes Fishes Atlantic Salmon Once very abundant in Lake Ontario 1 fisherman in 1800 s caught 400 in one night averaging 15 lbs each! Reports of salmon so numerous people were fishing with pitchforks Extinct by 1930 s Obstacles to Restoration Habitat remediation Clear, cold water Gravel substrates Passage for migrations Exotic species Competition with Pacific salmon, steelhead Predation from sea lampreys Can achieve length of over 6 ft and a weight of over 200 lbs Lake Sturgeon Feeds on soft-bodied benthic invertebrates and fish Nearly went extinct in Great Lakes Habitat destruction Overfishing 4

5 Lake Sturgeon Originally viewed as a nuisance species destroyed fishing gear Became valuable Caviar Meat Isinglass from swimbladder (foods, glass) Even burned in steamships! Vulnerable due to slow growth, maturation Important native piscivore prefers dim light Walleye Historically supported commercial fishery throughout the Great Lakes Fishery declined after 1950 s World-class fishery in Lake Erie Concerns about extinction in 1970 s Mercury concerns closed fishery, rebound Blue Pike Lake Whitefish Subspecies of walleye, now extinct. Smaller size, larger eyes Historically one of most harvested fishes Declared extinct in 1972, but rumors persist! Preferred deeper, cooler water Decline due to increased eutrophic conditions larval predation from smelt Overfishing and possible hybridization Salmonid prized for delicious, smoked meat Small mouth and large scales Feed near bottom in deep, cold water Important commercial fishery, not common in recreational fisheries Recent decreases in size, condition, lipid content More Dreissenid mussels, fewer Diporeia Most valuable fishery in Great Lakes in early 1900 s Lake Trout Widely distributed in colder regions of North America Feed on chubs, sculpin, rainbow smelt, alewife Overfishing and lamprey invasion decimated lake trout in 1950 s Extinct everywhere except Lake Superior Maintained today by extensive stocking Obstacles to Restoration Sea lamprey control still needed Competition from Pacific salmon Spawning habitats t Thiamine deficiency Causes early mortality syndrome (EMS) Thiaminase in prey, especially alewives 5

6 Sea Lamprey Sea Lamprey Life Cycle Most destructive invasive species in Great Lakes history Native to Atlantic Ocean and Lake Ontario Spread throughout Great Lakes via canals by 1947 Sea lamprey populations reduced by 90% by control programs expensive! One adult lamprey consumes lbs of fish in its lifetime Control Methods Chemical (TFM) primary control Barriers and traps Sterile male release Pheromones 6