Didymosphenia geminata (Didymo)
Found in the Gunpowder

-Submitted by John Brognard, Conservation VP
Mid-Atlantic Council - Federation of Fly Fishers

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Didymo or Rock Snot has been discovered in the Gunpowder River. Didymo has also invaded streams in West Virginia, Virginia, numerous streams in the West and North East and even streams in Alaska. Didymo grows profusely and eventually smothers the small insects in the stream. As a result the fish starve. At this time there is know known way to stop the infestation in a stream. We can only hope to prevent the spread to other streams by becoming better stewards of our environment.

In May 2006, EPA Region 8 and the Federation of Fly Fishers co-sponsored an international symposium on an emerging issue, the phenomenon of Didymo. Here is a excerpt from the white paper published by the group: “The diatom Didymosphenia geminata (Lyngbye) Schmidt is emerging as an organism with anextraordinary capacity to impact stream ecosystems on a global scale. In recent years, streams in New Zealand, North America, Europe, and Asia have been colonized by unprecedented masses of “Didymo” and its extracellular stalks. This diatom is able to dominate stream surfaces by covering up to 100% of substrate with thicknesses of greater than 20 cm, greatly altering physical and biological conditions within streams. This species is expanding its geographic range in North America and the rate that nuisance blooms are reported by the public and local media are increasing, yet little scientific investigation of the phenomenon in North America has been initiated.”

The white paper is available on the Mid-Atlantic Conservation website. I urge everyone to take the time to read the information. If you are not able to access our site or read the information I will be glad to send you a copy of the article. Dan Neuland also provided an excellent article in the Frederick News Post.

Recommendations to prevent the spread of Didymo:

• Do not enter a different stream until all your equipment is thoroughly cleaned with water with a 5% salt solution, rinsing with clean water afterward. A second method is to thoroughly dry all your gear. This includes everything from waders, fly and spinning line, reels, swimming suits, boats, canoes and kayaks, anything that can transport the spores.

• Replace felt sole waders/wading shoes with rubber soles of some type, but remember the upper portion of the wading shoe may remain wet for some time. The spores can live in damp places for several days. Another choice would be to have a second or even a third pair of felt sole wading shoes.

• If you spot Didymo, report it immediately to the DNR fisheries (301-898-5443) or you may contact me and I will make sure to have it investigated and get the word out.

Clubs in our area are joining forces to build and place cleaning stations along all our local streams. The stations will provide information about Didymo and have a salt solution in a pan to clean gear. We hope to start deploying the stations during the first week of June.

Didymo can literally kill a stream, so my passionate plea to everyone using our streams for fishing, swimming or paddling is to take this scourge very seriously and make every effort to prevent the spread. If you would like to help deploy and/or maintain a station please contact me.

Click here for another article about Didymo with photos and distribution maps.

John Brognard
Conservation VP
Mid-Atlantic Council – Federation of Fly Fishers
jb@flyfishwebdesign
301.371.4205
301.676.7669