Didymo on the Westfork

I have floated the Westfork of the Bitterroot River a couple of times in the last week, before the water started pouring over the dam, and couldn't help but notice the large amounts of Didymo on the rocks and underwater brush. Now before you freak out and think the sky is falling, let's back up a little bit. For those of you who don't know what didymo (aka "rock snot") is, I will try to explain the little I know.

Didymo is a naturally occurring diatom that is found in almost every Western river that runs clean and cold. This diatom has received a lot of press as of late in places like New Zealand, Chile/Patagonia and some rivers in the U.S.. When didymo explodes on rivers, it covers miles of river and forms very large mats (up to 6-12" deep) and that choke off aquatic life. Didymo thrives on rivers that receive a lot of sunshine, which is most good trout fisheries. Once didymo takes hold of a river, it is almost impossible to eradicate. New Zealand was the first country to take a proactive position by banning the use all felt soled boots . This is just one way didymo is transferred from river to river. It also can be transferred via boats (both clinging to the bottom and sides as well as water stored in the boat itself), any type of clothing, fishing gear and birds. (By the way the picture to the right is NOT on the Westfork. It is a stock picture of a completely choked river by didymo.) Although we cannot control the spread through birds, the other ways didymo is transferred can be controlled. If you are taking your boat from one river to another be sure to wash it out completely and thoroughly with a 10% bleach solution before getting to your next destination. If you have felt soled wading boots, make sure to thoroughly wash them with at least a 10% bleach solution and let them COMPLETELY dry out. Most wader companies are now making rubber soled boots to help fight the spread of didymo. However, they too must be washed and dried. Currently, there are many states considering banning felt soled wading boots in attempt to stop the spread of didymo, as well as other "Aquatic Nuisance Species". As of this writing, Vermont and Maryland have bills in the House of Representatives awaiting approval. Alaska was the first state to enact any legislation and will ban all felt in SE Alaska in 2011 and state-wide in 2012.

After the first time I noticed didymo on the Westfork of the Bitterroot River, I called Chris Clancy, Montana FWP Fisheries Biologist for the Bitterroot River. Mr. Clancy immediately relayed my story via email to both James Craft, Research Scientist Flathead Lake Biological Station and Bob Wiltshire, Executive Director Center for Aquatic Nuisance Species. I received an email from all of the above parties asking if I could collect samples the next time I was on the Westfork. I collected two samples (the first 2 miles above Job Corps and the second 2 miles below Job Corps) which Mr. Clancy immediately sent off to be analyzed. I have to give props and thank Mr. Clancy for his prompt actions regarding this matter. For those of you who follow my blog, you know that I have had some harsh words for Mr. Clancy. However, during this process he has been great to work with and his reposnses have been immediate. Mr. Clancy also informed me that there will be someone on the Bitterroot River this summer from the Center for Aquatic Nuisance Species that will be sampling the river for invasive species. When I find out more information on this issue I will follow up with another blog. In the meantime, I do not think we are due for a full blown invasion of didymo. However, if we experience severe low flows this year, anything could happen. The best thing anyone can do is practice the good preventative measures described above.