Rock Snot (Didymo)

Rock Snot, also called “Didymo” (Didymosphenia geminata), is a species of diatom that grows in shallow waters.  It is native to the Northern Hemisphere in areas including Europe and Asia.  More recently, rock snot has been found in North America and in New Zealand.  A single drop of water can transport this fast-growing microscopic algae.

Impacts

Didymo forms large mats on bottoms of rivers, streams and lakes. These mats can grow so large and dense that they destroy critical habitat for fish and prey species and disturb spawning areas. Didymo is transported by fishermen’s waders and equipment as well as flowing water.

Rock Snot “Didymo” (Didymosphenia geminata) Identification
This is a species of diatom that grows in shallow waters.  It is native to the Northern Hemisphere, areas including Europe, and Asia.  It has more recently been found in North America and in New Zealand.  A single drop of water can transport this microscopic algae.  Didymo can form large mats on bottoms of rivers, streams and lakes that destroy critical fish habitat, prey species habitat and spawning areas.
Transportation:  Didymo is transported by fishermen’s waders and equipment as well as water flow.
Control:  A new research project (spring, 2009) at the University of Colorado at Boulder has discovered that high water flows greatly decrease the amount of didymo in the system.  This control method is still being researched and is not 100% proven yet.  Fishermen should take the follow precautions after fishing in didymo infested waters.  These methods will help reduce the spread of didymo.
Check: Before leaving the river, remove all obvious clumps of algae and look for hidden clumps. Leave them at the site. If you find clumps later don’t wash them down the drain, treat them with the approved methods below, dry them and put them in a rubbish bin.
Clean: Soak and scrub all items for at least one minute in either hot (60°C) water, a 2% solution of household bleach or a 5% solution of salt, antiseptic hand cleaner or dishwashing detergent.
Dry: If cleaning is not practical (e.g. livestock, pets), after the item is completely dry wait an additional 48 hours before contact or use in any other waterway.

Control/Management

A new research project (spring, 2009) at the University of Colorado at Boulder has discovered that high water flows greatly decrease the amount of Didymo in the system.  This control method is still being researched and is not yet proven.

Fishermen should take the follow precautions after fishing in Didymo-infested waters. These methods will help reduce the spread of didymo.

Check: Before leaving the river, remove all obvious clumps of algae and then look for hidden clumps. Leave them at the site, preferably in the sun to dry. If you find clumps later don’t wash them down the drain or sewer, treat them with the approved methods below, dry them and put them in a rubbish bin.

Clean: Soak and scrub all items for at least one minute in either hot (60°C) water, a 2% solution of household bleach or a 5% solution of salt, antiseptic hand cleaner, or dishwashing detergent.

Dry: If cleaning is not practical (e.g. livestock, pets), after the item is completely dry wait an additional 48 hours before contact or use in any other waterway.

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Black & Pale Swallow-worts | Giant Hogweed | Purple Loosestrife | Water Chestnut | Glossy Buckthorn | Eurasian Water Milfoil | Rock Snot, Didymo | European Frogbit | Japanese Knotweed