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Economic Consequences

We are still largely unable to account for the economic and biological damage wreaked by exotic invaders. Marine conservation biologists have reported that:

• A North American ctenophore is blamed for a
  $250 million loss in Azov and Black seas fisheries;
  
  
• The cost for controlling the Zebra mussel invasion
  in the Great Lakes is predicted to reach $1.8-3.4
  billion US by the year 2,000;
  
  
• Exotics contributed to the collapse of the
  Chesapeake Bay oyster fishery;
  
  
• We'd better start preparing for an invasion of
  green crabs.

Green Crab

Copyright Brenda Guild Gillespie 1999

Green crabs in ballast water first reached San Francisco Bay, CA, in 1989. By 1997, they had reached Coos Bay, WA, and just this year was found in Vancouver Island's Barkley Sound. Green crabs are a potential threat to BC oysters and clams, and may prey on young Dungeness and red rock crabs.

Conservation biologists also had this to say about green crabs: "The introduction and spread of Carcinus maenas has the potential to change coastal communities over much of western North America."

Health Consequences

We're also woefully ignorant about the potential health consequences of introduced species. In general:

• Non-indigenous species increase toxic threats
  to marine environments, and stimulate red tides;
  
  
• Other dinoflagellates and cysts originating in
  ships' ballast pose other threats;
  
  
• There are 61 species of toxic dinoflagellates worldwide.