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With the recent discovery that the invasive aquatic alga known as didymo or "rock snot" has spread further down the Delaware River, the Pennsylvania Fish and Boat Commission (PFBC) is reminding anglers and boaters that cleaning their gear is the easiest, most effective means of preventing the alga from spreading to other waters.

The Delaware River Basin Commission (DRBC) last week confirmed that on April 18 one of their biologists discovered large didymo blooms over a 40-mile stretch of the Delaware River extending from the area near the confluence with the Lackawaxen River downstream to the vicinity of Dingmans Ferry Bridge. This section of river includes portions of two National Park units: the Upper Delaware Scenic and Recreational River and the Delaware Water Gap National Recreation Area. With this discovery, blooms of didymo are now in approximately 100 miles of the river.

"We may not be able to eliminate didymo from the river, but we can do our best to slow its spread and to prevent it from spreading to other waters," said Bob Morgan, the PFBC's ecologist who studies aquatic invasive species (AIS). "Didymo cells can easily attach to any items or equipment contacting the infected water, including fishing tackle, waders and the bottoms of boats. It takes only one didymo cell to start a new colony of the alga. We urge anglers and boaters to 'Clean Your Gear!' before leaving a water and entering another one."

The PFBC recommends that anglers allow exposed equipment to completely dry before entering new waters. Allow equipment to dry to the touch, and then allow it to dry another 48 hours. Thick and dense material like life jackets and felt-soled wading gear will hold moisture longer, take longer to dry and can be more difficult to clean. Soaking equipment in hot water containing dishwashing detergent (2 cups detergent/2.5 gallons of water) for 20 minutes also will kill harmful AIS.

Cleaning boats and equipment with hot water (maintained at 140 F) by pressure washing or soaking is another effective method. If hot water is not available, a commercial hot-water car wash also makes an ideal location to wash boats, motors and trailers. At the other end of the temperature range, freezing items solid for at least 24 hours is effective. If cleaning, drying or freezing is not practical, please restrict the equipment's use to a single waterway.

The PFBC is coordinating with the DRBC, scientists from N.Y. and N.J., and the National Park Service to identify appropriate next steps, including further sampling of the river to determine if there are additional areas with didymo.

Didymo is not a public health hazard, but it can cause ecological damage by smothering other organisms which also live on the riverbed and support the food web for the resident fish community. It's been called "rock snot" because of its gooey appearance. Its scientific name is Didymosphenia geminata.