ANNAPOLIS, MD (December 16, 2009) — The Maryland Department of Natural Resources (DNR) announced today that didymo, an invasive non-native algae has been found in the Savage River below Savage River Reservoir. DNA tests by fisheries managers earlier this year indicated the likely presence of this troublesome organism, but the findings could not be confirmed until DNR Fisheries staff found a small mass of the material in late November near the Allegany footbridge.
“The confirmation of didymo in the Savage is troubling,” said DNR Inland Fisheries Director Don Cosden. “We are concerned about potential impacts to native brook trout populations here and upstream of the Reservoir as well. We are also concerned that the algae could spread to the North Branch of the Potomac River below the Jennings Randolph Reservoir, a prime trout fishing habitat.”
Didymo is an algae diatom that sometimes forms dense mats. It is not a threat to human health but it can cover the stream bottom and suffocate beneficial organisms. It can also create difficult fishing conditions, fouling lines and terminal tackle. The mats may persist even after the algae dies, causing habitat damage for an extended period of time. Didymo, also called “rock snot”, looks slimy, but feels like wet wool or cotton, and can be white, brown or yellow.
Didymo first turned up in Maryland in 2008 in Gunpowder Falls below Prettyboy Reservoir. Subsequent monthly DNR surveys in the Gunpowder watershed have shown that densities peak in late winter, particularly in the Falls Road area. It is too early to tell how didymo may impact aquatic insects and other important organisms in the food web.
Didymo has been spreading rapidly into clean cold streams along the Eastern Seaboard for the past few years. These streams are prime habitats for trout and the organisms that support them.
Didymo’s appearance in popular trout fishing areas indicates that it is being spread by anglers. Felt-sole boots used by anglers are understood to be a major contributor. DNR is encouraging anglers to replace their old felt-soled boots with the new sticky rubber-soled models, which are much easier to clean and disinfect.
Anglers and outdoor enthusiasts can help prevent the spread of this and other unwanted aquatic invaders by thoroughly cleaning and drying all gear that has been in the stream. Scrub away all dirt and debris before leaving the area. DNR has set up wader wash stations at some key access areas where anglers can disinfect boots in a 5 percent salt solution as they leave the stream. DNR also recommends washing with a salt solution or with common dish detergent when you return home to avoid carrying didymo to your next fishing destination.
(Note: Photos are NOT actual algae samples found in Maryland but are instead images solely to demonstrate what didymo algae looks like.)