Impacts of Aquatic Invasive Species on the Lake Superior Fishery by Jeff Gunderson Minnesota Sea Grant Program
Can humans really impact the fishery of such a large waterbody?
Lake Superior Fishery Change Invasive Species cause of the greatest fishery impacts Chemical Pollution Sedimentation Commercial Fishing Recreational Fishing Habitat Loss
55 Non-Native Species in Lake Superior (Only 33 Native Fish Species) FISH (n=21) Alewife American eel Brook silverside Common carp Eurasian ruffe Freshwater drum Goby, round Goby, tubenose Goldfish Rainbow smelt Sea lamprey Stickleback, fourspine Stickleback, threespine White perch 7 Trout/Salmon INVERTEBRATES (n=21) Asian clam Bosmina coregoni (zooplankton) Cyclops strenuus (zooplankton) Echinogammerus ischuus (shrimp) Eurytemora affinis (zooplankton) Gammarus fasciatus (shrimp) New Zealand mudsnail Spiny waterflea Ripistes parasita (worm) Rusty crayfish Vejdovskyella intermedidia (worm) Zebra and Quagga mussels Other (n=13) 9 parasites and diseases 4 submerged/wetland plants
Environmental impact of two invasive species with the most demonstrable impacts Lamprey Atlantic Ocean via canals Smelt Atlantic Ocean via stocking
But first a description of two Lake Superior fish that endured precipitous declines not caused by invasive species lake sturgeon and brook trout Lake Sturgeon Unique fish Long lived Slow maturing
Thousands of Pounds Lake Superior Lake Sturgeon Production 140 120 100 80 60 40 20 0 1885 1891 Overfishing, habitat destruction, and dams caused decline of lake sturgeon 1897 1903 1909 1915 1921 1927 1933 1939 1945 Year Dramatic declines already by 1900 1951 1957 1963 1969 1975 1982 1988 1994
Coaster Brook Trout Lake Superior brook trout remain close to shore and historically spawned in 118 tributaries Provided a great sport fishery
Causes of Decline? Overharvest Primarily sport fishing Minnesota Historical Society Significant declines already apparent by 1880
Overharvest Causes of Decline? Stream habitat degradation
Research and management efforts toward rehabilitation are underway
Now, Invasive Species Induced Impacts SEA LAMPREY Most devastating invader in Great Lakes
What prevented lamprey from entering the upper Great Lakes? Niagara Falls:
Welland Canal Opened access to upper lakes Welland Canal was completed in 1829 Welland Canal was deepened in 1919 First sea lamprey in L. Erie 1921
Lake Trout a Valuable Fishery Wisconsin Historical Society Minnesota Historical Society Lake trout were the top predator and provided a commercial harvest of 4 to 6 million lbs. annually Photo: MN Historical Society
Thousands of Pounds 6000 5000 4000 3000 Lake Superior Lake Trout Lamprey first found in Lake Superior Sea lamprey caused lake trout extinction in Great Lakes, except Lake Superior Heavily impacted whitefish, burbot, walleye, suckers, rainbow trout, brown trout 2000 1000 0 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 Note: Commercial harvest data doesn t perfectly reflect changes in abundance because of changing net efficiencies, changing market demand, and changed regulations. 1957 1961 Years 1965 1969 1973 1977 1981 1985 1989 1993 1997 http://www.glfc.org/databases/commercial/commerc.php
GLFC Sea Lamprey Control Based on life cycle, focused controls in streams Prevent upstream spawning migration of adults mechanical and electrical barriers, trapping Kill juveniles in streams with selective chemicals Sterile male releases to reduce viable eggs produced. Attractants and repellants
Lamprey Chemical Control Photo: MI Sea Grant First TFM application Lake Superior, 1958
Lake Trout Rehabilitation after 50 Years Self-sustaining populations in most areas Stocking of hatchery reared fish has ceased in many areas Abundance is at or exceeds historical levels in many areas
Sea lampreys continue to kill as many or more lake trout than humans, but recovery has succeeded.
Siscowet Fat Lake Trout Not found in other Great Lakes
Lean 15% fat Lake Trout Forms Lean Lake Trout Siscowet 40-67% fat Siscowet Lake Trout
Siscowets are approximately 14 times more abundant than lean lake trout The State of Lake Superior in 2000 http://www.glfc.org/pubs/specialpubs/sp07_2.pdf Siscowets Siscowets also appear to have experienced a strong recovery from lamprey devastation Lean lake trout
Photo: MN Historical Society Lake Superior Cisco Fishery Ciscoes were formerly called lake herring Historically, most abundant native fish Ciscoes Supported an annual commercial harvest of 10 to 15 million pounds
Lamprey Lake trout Lake trout ate cisco Therefore, Cisco should Millions of pounds of lake trout disappeared because of lamprey -- so many more millions of pounds of cisco were not be eaten by lake trout therefore, cisco numbers were expected to dramatically increase
Thousands of Pounds Instead, cisco numbers declined 25000 Lake Superior Cisco Harvest 20000 15000 10000 5000 Lake Trout Nearly Gone 0 1900 1906 1912 1918 1924 1930 1936 1942 1948 1954 Year 1960 1966 1972 1978 1984 1990 1996 http://www.glfc.org/databases/commercial/commerc.php
Rainbow Smelt Introduction Introduced into a MI inland lake in 1912 Found in Lake Superior in 1930s Found along North Shore in 1946 after which populations exploded
Rainbow Smelt Small coastal Atlantic Ocean fish Has had negative impacts on native species
Smelt Impacts Contributed to declines in native fish populations such as cisco and lake whitefish Herring Fisherman
1935 1939 1943 1947 1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 Thousands of Pounds 25000 Cisco and Smelt Production Note: Commercial harvest data doesn t perfectly reflect changes in abundance because of changing net efficiencies, changing market demand, and changed regulations, but I think it adequately portrays cisco decline and smelt rise and fall. 20000 15000 10000 Cisco Lake Herring Smelt 5000 0 Year http://www.glfc.org/databases/commercial/commerc.php
Pound net in Duluth-Superior Harbor Unlike the invasion of lamprey, smelt at least created a commercial fishery
It also created a party every spring in the good old days
Photo: WI Historical Society And more fun than anyone should have!
After 1979, smelt abundance declined and cisco increased. We re not sure why smelt crashed, but it was the increasing number of predators since the early 1980 s that has kept them in check.
Cisco Recovery Several strong year classes since their population lows in the 1970s Greatest biomass of prey fish Cautiously optimistic about future
1913 1918 1923 1928 1933 1938 1943 1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 1000s of Pounds Harvest 20000 18000 16000 14000 12000 10000 8000 6000 4000 2000 0 Cisco, Lake Trout, Smelt harvest and Lamprey Index Cisco Lake Trout Smelt Lamprey Index Year http://www.glfc.org/databases/commercial/commerc.php Less predators and less forage fish (food) available than prior to lamprey and smelt
The Old Invasive Species had Significant Environmental Impacts Lamprey Atlantic Ocean via canals Smelt Atlantic Ocean via stocking A story of devastation and successful recovery. We have had dramatic declines in the most abundant and valuable fish in Lake Superior caused by the introduction of lamprey and smelt. These were both Atlantic Ocean fish that entered through canals (lamprey) or by intentional stocking (smelt). The impacts that they caused 40 50 years ago have largely been reversed.
There are many more recently introduced invasive species: What will their legacy be? Here already Ruffe 1986 Fourspine sticklebacks 1986 Threespine sticklebacks - 1987 Spiny waterfleas - 1987 Zebra mussels - 1989 Round gobies - 1995 New Zealand mudsnails 2001 Quagga mussels - 2005 Coming soon? Bloody red shrimp VHS virus Fishhook waterfleas Others?
Only time will tell Thank you