Several years ago the fly fishing world was forever changed by Didymo. From felt soles to washing waders, fly lines, etc. the end of the world was near. Besides the signs that say to your waders before entering the waters, Didymo has disappeared from print.
I've heard that the spring runoffs take care of it for us, but that sounds too easy.
Felt is still allowed in many states and I'm tired of busting my butt using the slippery rubber soled wading boots.
Anyone have any news?
Yes, I have news that you have not heard. You might just be the last person who has not heard that
felt boots are NOT causing dydimo blooms. The dydimo blooms are caused by low phosphorus in the water.
Dydimo has been it the North America for hundreds of years. Dydimo was present in North America in as early as 1218 AD, in the sediment at the bottom of Naknet Lake dated by a volcanic eruption. So who brought didymo to Alaska well before any Europeans even know it existed?
'We found no statistically significant change in the numerical presence of D. geminata or D. clavaherculis, as a group, in Naknek Lake between the years 1218 and 2003."
Historical abundance and morphology of Didymosphenia species in Naknek Lake, Alaska
The dydimo blooms are caused by low phosphorus in the water.
Max Bothwell, a research scientist for Environment Canada, who wrote an influential article that linked angler's felt soled boots to dydimo spread has now reversed himself and said that anglers are not responsible.
Here is his original article, On the Boots of Fishermen:
https://www.tandfonline.com/doi/abs/10.1577/1548-8446-34.8.382
He now believes that dydimo has been in North American waters and that it is a change in water chemistry, specifically
lower phosphorus levels that has
caused dydimo blooms.
Read the article in the current issue of American Angler, July-August, 2013, pp 8-9.
"'I no longer believe the problem is North American streams is the result of it (dydimo) being moved around.' …. Scientists are now convinced that dydimo lives in many streams, but blooms only when the water has far less than the normal amount of phosphorus…… The most damaging dydimo episode in the US seems to have been on Rapid Creek in South Dakota, where a six-mile bloom dramatically impacted a blue ribbon brown trout fishery. In 2007 and 2008, Bothwell and other scientists added phosphorus to sections of Rapid Creek. Sure enough, the dydimo mats shrank"
He published his findings in Freshwater Biology (2012) 57, 641–653 in an article titled:
Didymosphenia geminata growth rates and bloom formation in relation to ambient dissolved phosphorus concentration
"The blooms were present only in rivers where average dissolved P was very low. Didymo in higher nutrient waters had higher cell division rates, shorter stalks, and did not form blooms.
…. the blooms are caused by low nutrients in the overlying water, which promotes excessive stalk production. Subsequent surveys, experiments and observations in New Zealand have all been consistent with low nutrients (specifically low P) driving the blooms."
What causes didymo blooms
I think this recent discovery makes more sense than the old theory that all of a sudden dydimo sprang due to anglers boots when anglers have been using these same rivers for over a century with no dydimo blooms.
What is causing the dydimo blooms, I surmise, is the current trend of reducing phosphorus in laundry detergents and lawn fertilizer. So as we get rid of phosphorus to prevent algae blooms we get dydimo blooms.
Ever wonder why NZ has such a problem with dydimo? They have lots of crystal clear streams and rivers with low phosphorus because there is little run off from agriculture and lawns.
Basic epidemiology 101 states that we cannot stop the spread of what has already spread. How we then prevent disease is to make the target population less receptive to the disease. We allow the addition of some phosphorus into fertilizers in the river drainage of these dydimo affected rivers.
Secondly,
there is no single chemical decontamination method that will kill all invasives WITHOUT damaging the waders and boots. Now that it has been established that felt soles are not responsible for dydimo blooms, the worst invasive is the New Zealand Mud Snails. They are resistant to chemicals and felt is NOT where they hide. They hide IN the boot, under the footbed and any crevice.
A study by the California Department of Fish and Game found hundreds of NZ Mud snails lodged inside the crevices of individual test boots.
Over 50% of them were less than 1 mm in diameter. Replacing felt with rubber is not going to stop them.
"The majority of NZMS recovered were associated with wading boots. NZMS were observed on the tongue area of wading boots, associated with the laces or the area of the tongue that was tucked beneath the lacing eyelets. Large numbers of small NZMS were present inside of the boots, having worked down between the boot and the neoprene bootie of the wader. If the boots contained padded insole inserts, NZMS were also found underneath the inserts, associated with sand grains. NZMS were recovered from every treated set of wading gear. Numbers of NZMS per sample ranged from 1 to 227 with a mean of 33 (Appendix 2). Over 50% of NZMS recovered were < 1 mm in size (Table 4)."
http://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=3867
Finally,
New Zealand has the most rigid laws (The fine for spreading invasives is 5 years in Prison and/or a $100,000.00 fine). Yet
this has not stopped the spread of invasives.
We have 300 times the population of New Zealand, small fines and no jail time; and yet there are those that believe that rubber soles will stop the spread of invasives. Clearly that ignores the evidence.