SD Least Wanted.comAquatic invasive Species

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Europe, Asia and parts of North America


Didymo is a tan, light brown, and whitish diatom that clumps in strands and feels cottony to the touch. When submerged it looks similar to wet bathroom tissue.


This diatom can form large masses and reduce the primary productivity of the stream. It may be a cause for the decline of trout in some areas of the US.

Range Expansion:

Didymo can attach to waders and other gear and can easily be transported to new areas when fishing multiple streams in the same day.

South Dakota Distribution:
Asian Carp Distribution Map

Keep Aquatic Invasive Species Out of South Dakota's Waters


  • Remove aquatic plants and animals before leaving any waterbody.
  • Drain water from bait bucket, live well, bilge and motor before leaving any waterbody.
  • Dispose of unwanted bait, fish parts, and worms in the trash.
  • Spray/wash boat, trailer, and equipment with high pressure hot water on your way home or at home -OR- dry everything for at least 5 days.
  • Always report questionable species.


  • Never release live animals or plants - this includes all aquarium species, bait, pets or water garden plants. Do not release these into the wild. If you cannot find another home for animals, dispose of them in a trash can or bury them. Seal plants in plastic bags and dispose.


Because these hitchhikers can:

  • Reduce game fish populations
  • Ruin boat engines and jam steering equipment
  • Make lakes/rivers unusable by boaters and swimmers
  • Dramatically increase the operating costs of drinking water plants, power plants, dam maintenance, and industrial processes
  • Reduce native species
  • Degrade ecosystems
  • Affect human health
  • Reduce property values
  • Affect local economies of water-dependent communities.
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