Didymo Warning by Byron Begley

Warning!  There is a biological change that has the potential to also change fishing as we know it today.  The culprit is Didymo or as it is commonly called “Rock Snot”.  Didymo is a microscopic algae or diatom that has the ability to grow and form large mats that can affect stream habitats and food for fish. The diatom can cover a stream bed. I know many anglers know about this but I feel the topic should be discussed often to educate those who are unaware of Didymo.

Didymo has been around for a long time.  It was very common in China, Scotland, Sweden and Finland and it’s presence was recorded in the late 1800’s. Ditymo occurred in low nutrient water.  It was also described to be in North America in British Columbia in the late 1800’s. 

So why worry about something that has been around and written about for over 100 years?  Well for one thing, Didymo has spread lately to areas beyond it’s historical range.  And it now thrives in what were once considered non-threatened ecosystems.  This invasive diatom has adapted to waters in the United States and other Countries and it is happening fast. 

Also, the new Didymo is producing excessive growth.  In other words even in it’s historical range it is getting worse there.  This stuff is trying to take over. 

Just Google Didymo and you will find white papers, definitions and everything I saw and repeated above.    According to Wikipedia, Didymo was found in the Clinch River below Norris Lake, the South Holston tailwater and the Holston River below Cherokee Dam in 2005.  They say this was the first finding east of the Mississippi River.  Now we know it lives in the Watauga tailwater.  And these are nutrient rich streams contrary to the type of  ecosystem where Didymo only occurred a few years ago. 

Didymo has spread to many streams in the Northwest United States and the White River in Arkansas.  They found it in New Zealand recently and some strong regulations about waders and boat sterilization have been implemented to stop the spread.  Those people in New Zealand are scared to death and they should be. 

What you won’t find online is why it spread, why it has become more adaptive, why it is growing thicker and you won’t find any solution to the problem except trying to stop it from being introduced to new streams and lakes.

That is not easy.  One drop of water from a contaminated river can introduce the diatom to a new stream.  Just one drop of water.  This stuff can live in the felt of wet waders, in the bilge or pump on a boat, and when either are placed in a new stream the species can be introduced.  It’s that easy.  Everything you read will tell you that.

There are steps you can take to kill Didymo on your equipment.  That equipment would include waders, boat trailers, boats, inflatable craft, kayaks, canoes and possibly flies, reels and fly lines.  Some of these steps are feasible and would stop the spread of Didymo if everyone practiced them.  Here they are:

1.  Before leaving the river or lake remove clumps of algae.  Leave them on the river bank.  Don’t wash the clumps down the drain at home. So, brush off you waders, boots and boats before you go home.  This one sounds simple enough but you need to do more.

2. Soak and scrub your gear in 60 C water for at least one minute.  That will kill Didymo according to what I have read.  That is 140 degrees Fahrenheit. I wonder what that will do to the glue on your wading shoes and waders?  It might be OK, I don’t know.

3. Soak and scrub your gear in a 2% solution of water and household bleach. A gallon = 128 ounces.  2% = 2.56 ounces.  I would be safe and add 3 ounces of bleach.  Will this lessen the life of your waders over time?  I can’t find an answer to that. 

4. Scrub and soak your gear in a 5% solution of water and either salt, antiseptic hand cleaner or dishwashing detergent.  You would need to add 6 ½ ounces of either of these to make your gallon of disinfectant.  I can’t imagine that either of these would harm your gear.  Running this solution through cooling system of your outboard motor might not be a good idea.  Check with your motor manufacturer.  Boats and outboards can hold water for a long time.  And remember, all it takes is one drop of water. 

5. Let your gear dry completely and after it is completely dry wait an extra 48 hours to kill Didymo.  Here is where felt soled wading shoes is a problem.  Felt takes a long time to dry.   

6. I read that freezing solid will kill Didymo.  Of course that wouldn’t work for your boat except in the worst winter months.  You could put your wading boots in the freezer. I think disinfecting and drying makes more sense.

Wading boot manufacturers are trying to work on this problem.  They feel it is possible that felt will be outlawed from use at some point here in the United States.  Simms, Korkers and Chota have brought new rubber soled wading boots to the market.  I guess we’ll see over time how well they stick to the rocks in the Smokies.  I have a friend who has been wearing a pair of the Chota boots for a while.  He likes them on the Clinch. We have a test pair here at the shop.  Some of the guys here have used them and thought they were fine in the Smokies. 

Will Didymo eventually find it’s way to the Smokies?  The Fisheries staff are doing their research.  I talked to a Didymo expert at Tennessee Valley Authority yesterday.  He doesn’t know for sure but he thinks the canopy and shade will be favorable for the Smokies streams.  Didymo must like sunshine.  But nobody knows for sure.  Didymo is a mystery right now and there is no known feasable cure.

Will everyone disinfect their boat and trailer after each use?  Will everyone disinfect their waders after each use?  We better do it.  This is not the time or the place for apathy.  Warning signs and Disinfecting Stations are popping up.  I talked to some folks a few months ago about putting a Disinfecting Station here at the shop.  The problem is, we don’t have a sewer system and Little River is nearby.  What if it gets into the ground water.  I’m not willing to take that chance until someone proves that it would be safe.  Disinfecting Stations should be located next to the infected streams.  They are doing just that in some states. 

In parts of New Zealand you have to carry a valid Clean Gear Certificate and an approved Didymo cleaning kit.  On some rivers boating is not allowed anymore. As of October 2008 felt soled waders are banned in that Country.  I guess if that happens here there will be a lot of felt soled waders and wading shoes in stores and warehouses that will be worth nothing, including yours.  What a dilemma we find ourselves in.

So what is the good news? Well, scientists have not seen a change yet in the fish population or aquatic invertebrates in our infected tailwaters according to a TVA website. And we can take personal responsibility to help stop the invasive species from infecting other streams if we'll do it. Waders and boots should be disinfected and dried. We should do the same with boats and trailers. I don't see how you can completely disinfect a trailer with the boat sitting on it. Those carpeted boards that come in contact with your boat will be hard to treat and dry. We should disinfect outboard jet pumps somehow and disinfect the cooling system of all outboards. Canoes, kayaks and personal watercraft need to be disinfected. And, we can hope and support science to figure this mess out and do something about it if that is possible.