Wednesday, February 8th, 2023
Wednesday, February 8th, 2023

Breaking News for

Sportsmen Since 1967

‘Rock snot’ suddenly the newest invasive concern

By Don LehmanContributing Writer

With the fight against one dreaded fisheries invader still
ongoing, state officials are closely watching the appearance of
another potentially devastating invasive species just a short
distance from New York state.

A gruesome algae known as ‘didymo’ was confirmed to have made
its way into two prime Vermont trout streams as of mid-July, and
biologists there were warning it could devastate trout waters where
it spreads.

The algae has caused huge problems in New Zealand, where it
coats river bottoms and smothers aquatic life that trout depend on.
It also has recently gotten footholds in some southern states and
parts of Canada.

Its scientific name is didymosphenia geminata, but it’s called
‘rock snot’ because of its resemblance to mucus and slickness when
it coats river bottoms. It’s apparently native to cooler, northern
waters, but over the past two decades has started to expand its

It favors cool, fast, nutrient-poor waters, and the trout
streams of the Adirondacks and Catskills would seem to be prime
territory for it should it make its way west. It also spreads
easily, with it taking just one cell to begin development.

New York Department of Environmental Conservation spokeswoman
Lori O’Connell said the agency was aware of the arrival of the
algae in Vermont, but said there has been no confirmed reports of
it in New York.

Rich Preall, a DEC fisheries biologist in Region 5, said ‘it
would be very bad’ if didymo made its way into New York’s

‘It’s a mucus-like covering that gets all over the rocks,’ he
said. ‘It gets everywhere.’

In New Zealand, those who use waterways and don’t take proper
precautions to stop its spread can be fined thousands of dollars,
he said.

Its arrival in New York would be another big headache for an
agency still dealing with the ramifications of viral hemorraghic
septicemia (VHS), a fish-killing disease that has been found in the
Great Lakes system and a pair of Finger Lakes – Conesus and

‘We’re so busy looking for VHS. Every time someone finds a dead
fish the phone rings,’ Preall said. ‘It’s one thing after

Didymo was confirmed in the Upper Connecticut and White rivers
in Vermont earlier this summer, the first discovery of it in the

One guide who saw it in the Connecticut River and also had seen
the damage it caused in New Zealand warned of dire consequences in
an article in the July 11 Rutland (Vt.) Herald newspaper.

‘It will destroy the aquatic insect population and, in turn,
will destroy the wild trout population because there will be
nothing to feed on,’ guide Lawton Weber told the Herald.

Fisheries officials from around New England held an emergency
meeting July 13 to discuss ways to stop the spread of the algae.
George Crombie, Vermont’s natural resources secretary, called it
‘imperative’ that ways be found to control it.

No predators or apparent ways to kill it have been found once it
becomes entrenched in a waterway.

It sticks to boats, waders and other clothing that comes in
contact with it, and can live for weeks outside of water and on
clothing such as wader felt soles.

Freezing waders or using a bleach or detergent solution to kill
the algae seem to be the best way to kill the microscopic didymo
cells that linger on clothing or waders.

Vermont officials urged anglers and other water recreationists
to institute New Zealand’s recommended procedures for preventing
the introduction and spread of didymo: Check, Clean and Dry.

Check: Before leaving a river or stream, remove all obvious
clumps of algae and look for hidden clumps. Leave them at the
affected site. If you find any later, do not wash them down drains;
dispose all material in the trash.

Clean: Soak and scrub all items for at least one minute in
either hot (140 degrees F) water, a 2 percent solution of household
bleach or a 5 percent solution of salt, antiseptic hand cleaner or
dishwashing detergent.

Dry: If cleaning is not practical, after the item is
completely dry to touch, wait an additional 48 hours before contact
or use in any other waterway.

Share on Social


Hand-Picked For You

Related Articles