Alien species in the Hudson: an overview

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Alien species in the Hudson an overview
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What is an alien?
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A definition

• An alien species is one that was moved outside of
  its native range by human activities
• Usually applied only to species established in
  the wild (doesnt include wheat or chickens)
• Also called exotic, non-native, non-indigenous,
  introduced, or invasive species

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How many alien species live in the fresh waters
of the Hudson basin?

• Where did they come from?
• When did they arrive?
• How did they get here?
• What ecological effects have they had?

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More than 100 species, including many of our most
familiar plants and animals
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Aliens began to arrive a long time ago and are
still coming
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The aliens came from all over the world

• Canals
• Shipping
• Agriculture
• Stocking

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Aliens in the Hudson

• Many species
• Began arriving a long time ago
• New species still arriving
• 6-7 species/decade
• About 15 have strong effects, so
• A new strong species every decade
• Types of species linked to specific human
  activities

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Effects of aliens in the Hudson
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Zebra mussels
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Spread of zebra mussels in the Hudson
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Filtration rate of zebra mussels
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Impacts of zebra mussels
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Control options for zebra mussels

• Can be controlled in industrial settings (power
  plants, drinking water intakes) by chemicals,
  mechanical scraping, pipe coatings (267 million
  so far)
• No known or likely control in most natural
  settings

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E. Blair, NYSDEC
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but that so fine a plant as this, with its
handsome leafy rosettes, and edible nuts, which
would, if common, be as attractive to boys as
hickory nuts now are, can ever become a nuisance,
I can scarcely believe
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Lots of water-chestnut in the Hudson
of area
River kilometer
NYC
Albany
Findlay, Nieder, Barnaba et al.
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Impacts of water-chestnut
Caraco and Cole

• Impediment to recreation
• Depletes oxygen
• Removes nitrate (nitrogen)
• Changes animal community

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Eradication efforts

• 2,4-D and hand-pulling, 1961-76
• Beds reduced in size by 60
• Control abandoned because of herbicide
  regulations and changing priorities
• Beds as large or larger than before control

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Aliens in the Hudson (2)

• Some species have huge ecological effects
• Control difficult or never tried
• So effects are long-lasting or permanent

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New aliens continue to arrive
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Chinese mitten crab
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Northern snakehead
Asian clam (Corbicula)
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Round goby
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• The five carps
• Deliberately introduced 1850-2000
• Supposed to be desirable
• Widely distributed and spreading
• Negative ecological impacts
• Hard or impossible to control

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Etc., etc., etc.
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Conclusions

• The Hudson is full of alien species
• These species arrived here as a result of
  specific, careless human activities
• Some of these species have large ecological or
  economic impacts
• These effects can be long-lasting or permanent
• Alien species will continue to arrive and cause
  problems until we change our behavior
• We could do a better job preventing the arrival
  of alien species