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Potential Steps Associated with a Dreissenid Response

An initial detection of dreissenids in a CRB waterbody would trigger a proposed action in the states of Washington, Oregon, Idaho, and Montana as well as British Columbia and Alberta via implementation of the CRB framework, the emergency consultation process, and state and provincial rapid response plans. Any waterbody in the CRB could be a potential location for the proposed action, from free-flowing rivers and streams, to hydropower reservoirs, and isolated water bodies. Access to any waterbody is dependent on the road network to each waterbody, and the amount of development and access sites available. Shallow areas close to public use access sites, such as boat launches and marinas, are the most likely locations where both dreissenid detections and proposed actions would occur because of the pathway of introduction (watercraft) and reality that any control action would need to occur in somewhat shallow water based on the ability to cordon off a waterbody.

Specific tasks associated with each action may include detection area isolation, sample collection, site monitoring, site preparation, fish and wildlife salvage, mussel treatment, equipment decontamination, site restoration activities associated with the control action (if necessary), and implementation of conservation and minimization measures and best management practices to avoid and minimize adverse environmental effects.

The following describes the types of most likely treatments and activities that would likely occur upon a detection of dreissenids. Note that these steps may occur concurrently, not necessarily sequentially, and incorporate elements of an incident command system.

1. Initial Detections and Notifications

Initial Detectios

An initial detection of dreissenids requires immediate steps and additional testing to determine the validity of the detection and the scope and extent of the potential infestation.

Communication relating to a dreissenid incident is either minimal, or extensive, based on the scope/complexity of the incident. The intent of any communication is to share the current and ongoing status of the incident. There are two essential types of communication—internal and external.


  • Internal communication is driven by the lead action agency/entity, who determines the extent of communication within his/her organization to raise awareness and develop a shared understanding of the status of the incident.

  • External communication is driven by the lead action agency/entity, who conducts a conference call with those that have jurisdictional responsibility for response/action, those that could potentially assist with response, those that have signed onto the Declaration of Cooperation, and Endangered Species Act Section 7 Consultation Leads (if appropriate).

Activate IMS

2. Verification

Mussel veligers (i.e., free-floating microscopic larvae) are sampled pulling a fine-mesh (mesh size of not less than 64 ‎μm and not more than 65 μm) horizontal plankton tows (WRP 2018). Plankton tow samples are analyzed for veligers using both visual and molecular techniques. Settlers (i.e., juveniles) and adult mussels are sampled via substrate samplers and other direct observations, such as shoreline surveys and SCUBA diving. Water quality data (e.g., profile readings recorded in the field, water chemistry samples for laboratory analysis, etc.) can be collected to provide insight into aquatic habitat conditions.

The Western Regional Panel and its member entities have adopted Building Consensus in the West guidelines for classifying water bodies for dressenids (WRP 2018):

  • Unsampled – Waterbody is not being sampled or monitored for dreissenids.

  • Undetected/Negative – Sampling/testing is ongoing and nothing has been detected, or nothing has been detected within the time frames for de-listing.

  • Inconclusive (temporary status) – Waterbody has not met the minimum criteria for detection.

  • Suspect – Waterbody has met the minimum criteria for detection.

  • Positive –Multiple (2 or more) subsequent sampling events that meet the minimum criteria for detection.

  • Infested – A waterbody that has an established (i.e., reproducing and recruiting) population of dreissenids.


The minimum criteria for detection is two independent lab results from the same sample using scientifically accepted techniques, such as cross-polarized microscopy, DNA-based polymerase chain reaction (PCR) assays, gene sequencing, and taxonomic identification.

List of recognized identification experts

Dreissenid mussel laboratories

3. Activate Incident Management System

Activating the Incident Management System advances coordination, communication, and response to a dreissenid introduction.

Generally, the lead action agency (e.g., the state or provincial fish and wildlife agency) initiates the Incident Command System upon official verification of a suspect detection of dreissenid mussels. The scope, scale and function of the ICS is determined based on the circumstances of the detection. The lead action agency may request assistance from other governmental and tribal partners, which may result in the development of cooperating agreements.


A rapid response may have one of several possible outcomes, such as containing the invasion to a given area, suppressing population densities to reduce the rate of spread, prohibiting high-risk transport vectors, or in the least desirable scenario, developing adaptive strategies to co-exist with the invader. Based on the evolving situation for new detections, the lead action agency will set the objectives for the response.  There are key steps integral to any such effort, including: (1) responding to and minimizing impacts of infestations; (2) providing timely and accurate information to managers, stakeholders and the general public; (3) providing for the safety of the public as well as all personnel involved at any stage of a response; and (4) coordinating with neighboring and regional jurisdictions on immediate response and long-term management, as appropriate. Developing a shared understanding of these important steps prior to a response is critical to effective prevention efforts, and greatly enhances the ability of jurisdictions to coordinate and cooperate.


Generally, the lead action agency involved will identify staff (both internal and external to the agency) willing to serve as Lead Action Agency Representative and response team staff. Joint command may be established for a response involving a waterbody where there are multiple jurisdictions. The Lead Action Agency Representative initiates a communications team, and engages the Columbia River Basin Interagency Response network as appropriate. 

To access Incident Management System forms specific to dreissenid responses, click here.


4. Delineate the Geographic Scope/Extent of the Incident

Delineate Scope

Delineating the geographic scope of the infestation helps inform the scope and potential impact of the infestation as well as any need for emergency restrictions. Delineating the scope and extent of the infestation requires intensive sampling efforts, which may include:

  • plankton tow sampling (microscopy analysis) and eDNA sampling in the infested area as well as upstream and downstream of the infestation;

  • examination of existing substrate samplers throughout the region, with an emphasis on water delivery and other entities with associated hydropower infrastructure;

  • a suite of methods to examine and potentially remove infrastructure in which dreissenids may attach; and

  • enhanced communication with property owners in and around the perimeter of the infestation to secure permission for sampling efforts.

5. Notifications and Communication

Notifications and Communication

Preventing further spread through containment strategies focused on pathways of spread is foundational to any new detection of dreissenids, and may include mandatory inspections, decontaminations, or closures. When closure of the waterbody is not possible, well-equipped watercraft inspection and decontamination teams should be deployed to inspect and decontaminate watercraft pre-launch and post haul-out.

Communication is integral to any containment strategy because containment strategies can affect boaters, other jurisdictions or management authorities, communities near waterbodies, and numerous other entities.

CRB Notification List

Sample Press Release

Sample Declaration of Emergency

Sample Executive Order

6. Containment


Preventing further spread through containment strategies focused on pathways of spread is foundational to any new detection of dreissenids, and may include mandatory inspections, decontaminations, or closures. When closure of the waterbody is not possible, well-equipped watercraft inspection and decontamination teams should be deployed to inspect and decontaminate watercraft pre-launch and post haul-out.

Communication is integral to any containment strategy because containment strategies can affect boaters, other jurisdictions or management authorities, communities near waterbodies, and numerous other entities.

7. Evaluate Response Alternatives

Evaluate Response Alternatives

Response to an introduction of dreissenids may lead to early detection rapid response actions, or containment and mitigation actions. 

If an action is deemed feasible (see below for more details on each):

  • Incorporate Endangered Species Act Best Management Practices

  • Incorporate Section 7 Consultation Requirements (if appropriate)

  • Obtain all necessary permits to implement the action

  • Obtain and organize resources

  • Implement the action

  • Evaluate the response

8. Determine if ESA Consultation is Triggered

Determine if ESA

Click here for guidance on navigating ESA Consultation issues.

9. Select Response Action

Select Response Action

Select the response action most likely to achieve control/containment goals and minimize detrimental effects to native and listed species.

10. Obtain and Organize Resources

Obtain/organize resources

Resources needed will depend on the response action that will be taken. For a potential list of resources available, click here.

11. Initiate Response and Implement Best Management Practices

Initiate Response/BMPs

Initial response activities include site mobilization, area isolation, and rescue/salvage.

Site Mobilization


Equipment expected to be used in any control effort: vehicles, boats, trailers, generators, small fuel and oil containers for small engines, pumps, hose material, silt curtains, portable water tanks, other barrier material, and treatment chemicals.


Site mobilization includes access and vegetation and wildlife considerations. Click here for Best Management Practices for each.


Area Isolation


The areas adjacent to public access site(s) where the detection of dreissenids is confirmed will be immediately closed to boat traffic, and any contaminated watercraft, including derelict vessels, will be removed. Isolation reduces the potential that dreissenid veligers or juveniles could escape the treatment area, which is important when the invasion is detected early and eradication is most likely. A barrier must significantly limit or eliminate water transfer from the treatment area to the main water body. Complete elimination of connectivity for the duration of treatment is preferred.

  • Establish mandatory decontamination procedures for all existing watercraft.

  • Collect samples inside and outside of the contaminated area for immediate analysis.

  • Determine the feasibility of using silt curtains or barriers to close the bay or marina to open water.


Isolation of a portion of the water body is intended to eliminate water transfer from the treatment area to the main water body and prevent the transfer of aquatic life from the main water body into the treatment area. Two methods commonly used to create this isolation are silt curtains and bladder dams.


  • Impervious silt curtains (Figure 3) would be deployed via boat (e.g., commercial silt curtain or HDPE material anchored in place), then secured to shore on the other end, or the boat can deploy the curtain in a circular fashion around the perimeter of a treatment area. Silt curtains can be up to 30.5 m in length, with a skirt of the same depth. Curtains can be fastened together to extend as far as necessary, whereas the skirts have a bottom chain for weight, and can be anchored to the substrate with sand bags.


The skirt is lowered, and sandbag anchors placed once the curtain has been appropriately stretched. This includes dropping the weighted skirt by untying or cutting, binding, and attaching and lowering sandbags into place.

Removal steps occur in the reverse order.


  • Inflatable bladder dams [e.g., PLUG (Portable Lightweight Ubiquitous Gasket) and Tiger (PVC-coated fabric) dams, high density polyethylene (HDPE) liner material] would be deployed by humans on foot.


Figure 3. Example of a deployed turbidity curtain.

Inflatable bladder dams (Figure 4) can be positioned across the substrate and pumped with water to effectively block connectivity.
This isolation method may be depth-limited.


Methods for bladder dam deployment may include:

  • Bladder dams are unrolled and waded into place on foot, and the bladders are then filled via water pumped into the bladder.

  • Any pump intake would be required to draw as specified by NMFS (2001) to protect juvenile fishes 20–30 mm.


Removal steps occur in the reverse order. If water is used from the water body being treated, the bladder water would receive treatment before being discharged.


Figure 4. Example of a deployed inflatable bladder dam. Source:



Methods that could be used to isolate a portion of the water body, in addition to silt curtains and inflatable bladder dams, may include geotextile fabric filled with an appropriate material as well as a combination of sandbags, polyvinyl chloride (PVC)-coated fabric, and blocks.


Water tracer dyes

To evaluate the effectiveness of containment barriers (regardless of type) after installation but prior to treatment, tracer dyes may be used. Water tracing introduces xenobiotic substances[1] into waters and are a potential source of water contamination (Behrens et al. 2001). The selection of a tracer depends on the receiving system, cost, ease of analysis, toxicity, ambient background concentrations, and the degree to which the tracer behaves conservatively (Runkel 2015). Fluorescent dyes used as water tracers should be readily soluble in water, conservative, stable through time, measurable at large dilutions, simply and easily detectable, low in toxicity, readily available and inexpensive, and not deteriorate upon contact with water as well as pose no significant health or environmental threats (Field et al. 1995).





In cases in which listed aquatic species are present, attempts should be made to rescue/salvage listed species (that would not naturally move away from the action area). The guidelines and protocols identified in Reynolds (1996) and NMFS (2000) for electrofishing would be implemented during fish salvage. For all other species, such as mollusks, gastropods, and crustaceans, all attempts would be made to rescue/salvage any listed species and retain them offsite, or move them into another portion of the water body where it has been determined they will not be affected by the action.

Best management practices minimizing impacts to these species would be developed in advance of implementation.


Fish salvage methods may include:

  • Boat or backpack electrofishing gear calibrated to the specific onsite water conditions (i.e., conductivity).

  • At least one team of three people would wade, or operate a boat throughout the treatment area, netting fish and placing them in containers of fresh water with air supply until no fish are captured for a period of 5–10 minutes. Number of teams and total collection effort would depend on size of the treatment area.

  • Fish would be transferred to a separate holding tank with uncontaminated water calibrated to the ambient treatment area water temperature with oxygen supply.

  • A clean water flush calibrated to the ambient treatment area temperature would completely replace the tank volume prior to fish release outside of the treatment area.

  • A separate crew with sanitary equipment would conduct the fish transfer via nets and smaller containers adjacent to the treatment area.

  • All equipment used during salvage would be treated onsite using the same methods as equipment sterilization (discussed below).


[1] Xenobiotic substances are synthetic chemicals generally not naturally produced.

To access information about Best Management Practices as well as strategies to prevent the introduction and spread of invasive species during a response, click here.


12. Initiate Post-Consultation with Federal Agencies, if Needed

Initiate post-emergency consult

To access information about post-emergency consultation with Federal agencies, click here.

13. Document and Share Lessons Learned

Document lessons learned

This toolkit is intended to use an adaptive management framework, which incorporates debriefings, after-action reviews, and incorporate of knowledge and lessons learned to inform future goal setting and planning. Every dreissenid action should include these elements to complete the adaptive management cycle and improve future responses to dreissenid introductions.


This version of the adaptive management framework was developed by the resource stewardship division at
Rocky Mountain National Park.

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