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The algae can spread easily to other streams, rivers
Warnings will soon be posted in the Delaware Water Gap National Recreation Area advising boaters and fishermen of a new invasive species of algae called Didymo, more commonly known as "rock snot" because of its goopy appearance.
Scientists in the past two weeks have discovered the algae from the Dingmans Ferry bridge in the Gap stretching about 100 miles north to upstate New York, where the river splits in its western and eastern branches.
"It might go all the way to Trenton," said National Park Service biologist Rich Evans.
This expanded range of rock snot was only confirmed in the past couple of weeks, and Evans said it's because of a change either in the environment or in the organism itself.
Didymo covers rocks like a sort of shag carpet, but has thrived best in colder waters than the stretch of the Delaware where it has now taken up residence.
It is that carpet-like growth, according to Evans, that keeps some fish species from laying their egg sacs on underwater rocks, and prevents caddisfly eggs from attaching to those same rocks as well.
Mayfly larvae like to feast on thin layers of other algae species that can also be found on underwater rock surfaces.
If rock snot crowds out the habitat for those flies, trout will lose a prime source of food.
Because its spores can easily attach to rubber wading boots and boat hulls, biologists are warning fishermen and boaters to clean any surface in contact with Delaware River water before going into any other body of water, including the trout streams that feed the Delaware.
"Wow," said Ernie Lisotto of Jersey City, N.J., who fishes almost every day from the Delaware down to the Jersey Shore.
Lisotto said he had never heard of rock snot but will take pains to clean his boots and boat now that he knows.
Evans said a light bleach mixture is best, but even dish detergent can make a difference.
Rock snot spores can live for up to 40 days out of water, suggests how easy it is for this invasive, fish-deadly plant is to spread.