Aquatic Nuisance - Didymo
Didymo (Didymosphenia Geminata)
- Originates in Europe, Asia and parts of North America.
- Rapid Creek in Pennington County in the Black Hills
- It is tan, light brown, and whitish that has clumps of ropy strands, a rough cottony feel and fibrous.
Where did it come from?
Where can it be found in South Dakota?
What does it look like?

Why is Didymo a problem?
- It can form in large masses driving out food sources for other plants and animals. It may be a leading cause in the decline of Brown Trout in Rapid Creek.
How is Didymo spread?
- Didymo can stick to anything (boats, fishing gear, and wading gear) it touches and be transported without the proper removal.
Check out Aquatic Nuisance Species Prevention on ways to prevent the spread of Aquatic Nuisance Species
Didymo links
Digital Frontier Fact Sheet on Didymo
Pictures of Didymo
South Dakota Didymo Distribution
SD AIS Species
A.I.S. Fish
Asian Carp
Common Carp
Western Mosquitofish
European Rudd
Snakehead
A.I.S. Invertebrates
Zebra & Quagga Mussels
Rusty Crayfish
Asian Clam
New Zealand Mudsnail
Red-rimmed Melania
A.I.S. Plants
Brittle Naiad
Didymo
Curlyleaf Pondweed
Flowering Rush
Eurasian Water Milfoil
Purple Loosestrife
