Past Projects

ISAN & Didymo

Past Project

Why didymo? Contrary to other algae species, didymo represents an interesting paradox where didymo mats form under very low nutrient conditions. Also, managers continue to grapple with how best to address this species when faced with extraordinary mat formations. For the past decade, ISAN has had an interest in this unique species because of its management implications.

The alga, Didymosphenia geminata, commonly referred to as “didymo”, is a freshwater microscopic diatom. It is found in streams and rivers across much of North America. Didymo attaches to the streambed by a stalk and it forms thick mats that can alter aquatic ecosystems. These mats have a rough texture similar to wet wool and can look like strands of toilet paper.

In recent years, streams in New Zealand, North America, Europe, South America and Asia have noted unprecedented masses of “didymo”. This diatom is able to blanket up to 100% of stream surfaces by with thicknesses of greater than 8 inches, potentially altering physical and biological conditions within streams.


Cleaning equipment between uses on different freshwater systems is important to prevent the spread of didymo and other invasive species. If you can follow the simple Clean, Drain and Dry steps, then you will do a world of good.

For decontamination methods specific to didymo, you can learn more from the links below in the report “Decontaminating Equipment”. For more information on general cleaning practices, go to cleanangling.org.

Other resources of note include:


The Conference was held on March 12-13, 2013 in Providence, Rhode Island USA and proudly hosted by the Invasive Species Action Network and Northeast Aquatic Nuisance Species Panel.

The conference successfully brought together natural resource managers, researchers, conservationists, fishing clubs and others with an interest in learning more about didymo.


For management recommendations, read the Management Challenges of Didymosphenia geminata.

For a complete list of presenters and conference agenda, download the Conference Booklet.

Conference presentations:

  • Aunins – Genomic characterization of D. geminata: current progress and future directions.
  • Cary – A sensitive genetic-based detection and enumeration method for D. geminata.
  • Gills – Impact of D. geminata presence on juvenile Atlantic salmon: A project overview.
  • Kilroy – Plenary Speaker: Didymosphenia geminata: an extraordinary organism.
  • Klauda – Didymo infestation in Maryland, USA: A state agency’s reactions, responses and Felt/Results.
  • Kuhajek – Laboratory-based experiments to investigate didymo distribution patterns in New Zealand.
  • Montecino – On the biogeography of D. geminata in Chile: niche requirements and potential habitats.
  • Nelson – Identification, enumeration and measuring cell dimensions of D. geminata using an imaging particle analyzer (FlowCAM).
  • Pillsbury – Are the recent blooms of D. geminata in Lake Superior (USA) caused by an aggressive strain on environmental changes?
  • Richardson – Spatial distribution and ecosystem effects of a nuisance, bloom-forming diatom (D. geminata) in Catskill Mountain streams, New York.
  • Sanson and Gerbeaux – D. geminata in New Zealand:an update on current managment and research approaches.
  • Spaulding – Paleolimnological records of Didymosphenia geminata in North America.
  • Sundareshwar – Does sulfation of Didymo stalks facilitate iron adsorption and phosphorus concentration in mats?
  • VanPatten – Missouri’s proactive approach to didymo.
  • Zarnetske – Integrating invasion history with environment to model D. geminata hotspots across New Zealand.
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Smith River Project

Past Program

In 2010, Montana Fish, Wildlife & Parks worked with ISAN to create invasive species outreach materials to influence the behavior of Smith River floaters about invasive species through the permitting process.

Smith River AIS Postcard

The program utilized three primary outreach contact methods. The first is the inclusion of information about AIS and protecting the Smith in the floater packet sent to all permittees.

The second contact comes via a post card mailed to the individual and timed to arrive about a week before their float.

The final outreach contact occurs at the Camp Baker put in where all floaters are required to receive an informational briefing from a Smith River Ranger.

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Riparian Weed Mapping

Past Program

A Collaborative Effort to Address Noxious Weeds

Riparian areas are among the most diverse and important components of our ecosystem. Healthy riparian areas act as filters to maintain water quality, reduce streambank erosion, maintain a higher water table, provide forage and shelter for livestock and wildlife, and provide recreational and fisheries values. However, riparian areas are especially vulnerable to weed invasion because they are easily degraded by natural and human-caused events. 

However, riparian areas are especially vulnerable to weed invasion because they are easily degraded by natural and human-caused events.

The presence of noxious weeds in Montana’s riparian areas is poorly documented. Many of these areas are difficult for a landowner to access and, in the case of many islands, it is not clear who the landowner is. It is important that we survey our riparian zones to determine the extent of weed invasion and to begin to understand how control might be implemented. 

The Riparian Weed Project is a collaborative effort that brings together recreationists, landowners and weed managers to work on weed mapping and control projects. Since 2009 we have been compiling maps of the presence of terrestrial noxious weeds along the river banks of some of Montana’s rivers. 

Riparian Weed Maps

ISAN has archived maps available to those interested in this historic data. Please contact us if you are interested in requesting this data. Maps available include: 

  • The Upper Yellowstone River, 2009 (Paradise Valley downstream to near Billings)
  • The Madison River, 2010 (Reynolds to Ennis Lake)
  • The Madison River, 2010 (Warm Springs to Silver Bridge)
  • The Madison River, 2011 (Reynolds Pass to Ennis Lake)


Read and learn more about weed issues and ways you can tackle them.

Montana State Extension Service

Montana Weed Control Association

USDA Noxious Weeds

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