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

Ricciardi et al 2001 Great Lakes Introductions increase over time

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) Hudson Erie Canal

 Thereafter invasion quickened; found in Lake Huron in 1932, Lake Michigan in 1936, and Lake Superior in  Gained access to Lake Erie through Welland Canal around Niagara Falls (completed 1829), but not noted in Lake Erie until 1921

 Lampreys devastated 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

 Euryhaline species  Traveled through canals (maybe native to Ontario) Alewife  Population expanded when lake trout died  Efficient zooplankton eater, changed zooplankton and contribute to decline of native fish (e.g. bloater)

Lake Trout Alewife Bloater Whitefish Large zooplankton Small zooplankton Sea Lamprey Pacific Salmon Phytoplankton

Ballast-mediated species Introduction uptake transport discharge

Water is used for ballast, but sediments accumulate too Can contain resting stages or live animals

Dreissenid Mussels  Ponto-Caspian origin  Ballast transport  First found in Lake St. Clair  Adults attach to substrate  Planktonic larvae  High population density  High filtration rate History Biology

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

Secchi depth (m) zebra mussels  Increase in water clarity in Oneida Lake, NY

Bay of Quinte; S. Millard, DFO Onieda Lake; CBFS Lake Erken; P. Eklov, Uppsala U. Naroch Lakes chain; L. Brulakova & A. Karatayev, Austin St. U. Western Lake Erie; S. Ludsin

NarochOneidaErieErkenQuinte NQuinte BMyastroBatorino Lake Mean annual Secchi depth (m) Mean pre-zebra mussel TP (ug/L) pre zebra mussel post zebra mussel pre zebra mussel

Some species extremely long lived, > 100 years Do not mature for relatively long time ~> 10 years Dreissena and Unionid Clams  Zebra mussels encrust unionid shells. Interference competition Populations already hurt by water quality problems and dams  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 inland lakes. Native Daphnia spp. short vs. long spine big vs. small body

 Feeds on smaller zooplankton in the Great Lakes  May be reducing food for native plankton and fish species Which would fish rather eat??

Round Goby  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 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.

Economics of electrical barrier Construction cost? Maintenance cost? Will it work? MN proposing bubble and sound curtain 57% effective

Lake Trout Alewife Bloater Whitefish Large zooplankton Small zooplankton Sea Lamprey Pacific Salmon Phytoplankton Zebra mussels goby Asian carp Spiny flea Benthic algae

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