With spring coming to the east and many a fisherman itching to shake off this year's long winter, it seems like a good time to call attention to a wonderfully informative short film about didymo, released last year by Jason du Pont. Most, if not all, of you have heard about didymo, and many others may fish or have fished in waters that have become infected with didymo. For those of you unfamiliar with Didymo, Didymo (Didymosphenia geminata), commonly known as "rock snot", is an invasive algae that thrives in some cold water habitats, forming thick mats on river and stream bottoms.

Despite familiarity with didymo and the threats it poses to the rivers we all hold dear, how many of us have seen didymo first hand? How many of us have experienced the impact of a didymo outbreak? Though we bear in mind the didymo threat and take precautions to avoid helping it spread to water bodies currently not infected but that remain under constant threat because of their proximity to infected streams or rivers, how sincere and extensive are those efforts, espeically for those of us that have no personal experience with the algae itself?

Jason du Pont's video, filmed over the course of many months on the didymo-infected Gundpower River in Maryland, shows the progression of the algae from its bloom in mid-winter through the spring as well as its impact on angling. The results are disturbing, to say the least, and that's taking into consideration that -- during Jason's filming -- abnormally high early spring flows greatly reduced the seasonal impact of didymo.

If you're not already taking precautions (such as not wearing felt soled boots and making sure to clean and disinfect water craft), hopefully Jason's film will set you on the right track. You can view the film below, but I'd recommend viewing it directly on Vimeo and in HD.


The notion that didymo is spread to rivers and streams via felt soles, laces, etc. (not to mention herons and osprey and eagles) has been refuted by science. After all the hysteria, it seems to be a function of stream chemistry (low phosphorous) - not the soles of your wading boots. Although a boon to the wading boot industry, it is now evident that all our efforts were in vain.