Didymo May Not
Be Quite as Lethal
As Feared
By Sara Nelson

Two fishermen cast their lines into the curves of the beautiful White River near Royalton. The recent discovery of the didymo algae in the White River about 10 miles upstream from hear has caused concern for the future of fishing in the river, but a new report indicates the problem may not be as great as feared. (Herald / Tim Calabro)

State officials heard some encouraging news about the invasive algae didymo, also known as rock snot, at an international conference held in August.

Since the algae was found in the White River in July, the state has worked quickly to contain the threat it could pose to fish populations, recreation, and the tourism industry. State and environmental organizations have posted signs at river access points identifying didymo and describing a simple disinfection method for river users.

At the Aug. 17 conference, officials learned that this quick response was "the best thing we could do," said Leslie Matthews, an environmental scientist with the Agency of Natural Resources.

There is no way to eradicate the algae, which can cover river bottoms with unattractive fibrous mats that lower the populations of insects that fish eat. However, officials learned that the threat to fish may not be as serious as was initially thought.

Matthews said the link between the presence of the algae and declining fish populations hasn’t been conclusively proven in places like New Zealand, where the algae has invaded.

Scientists estimate that some rivers in Europe and Norway have had the algae for about 100 years without damage to fish populations. In Canada, the algae has even shown some natural decline.

Another reason for optimism is the success in Vermont of educational outreach containing invasive freshwater zebra mussels.

Matthews said meetings were scheduled this week to formulate a statewide response that would likely include more outreach and educational methods to prevent the spread of the algae to other rivers in Vermont.

Despite the good international news, Vermonters are still encouraged to remove any visible clumps of algae clinging to boats, clothing, or fishing gear, and to scrub or soak the items in hot tap water with plenty of soap.

Mary Russ, executive director of the White River Partnership, said her organization is continuing efforts to educate watershed residents about didymo and how to clean equipment. Russ said she was encouraged to learn that didymo may not reduce fish populations in areas where studies have been completed, but cautioned that "it is important for people to remember that didymo is just one species on a long list of current or potential non-native invasive species that can threaten the health of the White River."

"Learning about invasive species and committing to ‘check, clean, and dry’ all equipment after every outing can not only stop didymo from spreading, but also prevent new invasive species from taking hold."

More information about didymo can be found at the Agency of Natural Resources web site, www.anr.state.us/#didymo.