Highly invasive alga found last year in several popular trout streams in the Northeast, Anglers considered an important vector in spread of didymo.

With Opening Day of trout season this weekend, the Connecticut Department of Environmental Protection (DEP) is reminding anglers and boaters to be on the lookout for the highly invasive freshwater alga Didymosphenia geminata, known as “didymo,” and to take precautions to prevents its spread into Connecticut waters.

In 2007, the presence of didymo was confirmed in the northern reaches of the Connecticut River (NH/VT), White River (VT), Batten Kill (NY/VT) and the East and West Branches of the Delaware River (NY/PA), all popular trout streams. These were the first official reports of didymo in the northeastern United States.

Didymo (commonly referred to as “rock snot”) is most frequently found in cold, relatively shallow streams and rivers having a rocky bottom, characteristics that are also typical of good trout habitat. During blooms, didymo can form thick mats of material that feel like wet wool and are typically gray, white and/or brown, but never green in color. These mats form on the bottoms of rivers and streams and can potentially smother aquatic plants, aquatic insects and mollusks, alter stream flow characteristics and fish habitat, and impact the food chain. Dense mats of didymo can also reduce the recreational and aesthetic value of the affected river.

Anglers may have contributed to the recent spread of didymo. The microscopic cells can cling to fishing gear, waders (felt soles can be especially problematic), boots and boats, and remain viable for months under even slightly moist conditions. Although didymo has not yet been found in CT, it has been found in near-by states. It is recommended that trout anglers, especially those who also fish streams outside Connecticut, practice CHECK, CLEAN, DRY procedures.

CHECK: Before leaving a river, stream or lake, remove all obvious clumps of algae and plant material from fishing gear, waders, clothing & footwear, canoes & kayaks, and anything else that has been in the water and look for hidden clumps. Leave them at the site. If you find any later, clean your gear and dispose of all material in the trash.

CLEAN: Soak/spray & scrub boats and all other “hard” items for at least one minute in either very hot (140°F) water, a 2% bleach solution, or a 5% dishwashing detergent solution. Absorbent materials such as clothes and felt soles on waders should be soaked for at least 40 minutes in very hot water (140°F), or 30 minutes in hot water (115°F) with 5% dishwashing detergent. Freezing thoroughly will also kill didymo.

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.

The above procedures will also be effective against other unwanted organisms.

Although didymo has not yet been found in Connecticut, DEP is taking additional precautions to prevent the introduction and/or spread of this and other invasive species. DEP’s Inland Fisheries Division is currently developing a formal “Biosecurity” policy for its field operations, with implementation to begin this upcoming field season. Also, as part of its outreach efforts on invasive species issues, DEP will be mailing an informational flier on didymo to many of the state’s bait & tackle shops this week.

An excellent source for information on didymo is the Biosecurity New Zealand web site www.biosecurity.govt.nz/didymo. Additional resources include the New Hampshire DES web site: www.des.state.nh.us/wmb/exoticspecies/didymo/index.html and the US EPA Region 8 website www.epa.gov/region8/water/didymosphenia/.