Decontamination and Disinfection Procedures

After collecting field samples from bodies of water known or suspected to contain live zebra mussels at any life stage, all field equipment used to collect those samples, or that was in some way in contact with the body of water, should be thoroughly cleaned before moving to another site outside the known range of the zebra mussel. Whenever practical, the least infested (or least likely to be infested) sites should be sampled first to reduce the risk of accidentally infecting a new area during sampling. If sampling is being performed to determine whether zebra mussels are present at a given site, assume that they are present and thoroughly clean all sampling equipment before moving to another site outside the known range.

Methods for equipment decontamination

Small equipment (nets, waders, boots, buckets, etc.)
• All field equipment needs to be visually inspected and all visible mussels removed and killed.

• All field equipment must then be cleaned by soaking, dipping in, or scrubbing with, one of the disinfectant solutions listed. If one of these approaches is not possible, the equipment should ideally be steam-cleaned or at least rinsed with water (hot and/or high pressure if possible) and allowed to dry completely before next use.

• Particular attention must be given to places where the mussels could be accidentally trapped, such as the treads of boots and waders, hinges of benthic grabs, etc.

   

  Large equipment (boats, trailers, etc.)
  Compartments:

• Bilges, wet wells, live wells, and any other compartments that could hold water from an infested field collection site should be drained of water at the field site, and if possible, flushed with disinfectant solution or hot water and allowed to dry before the next use. If appropriate, the field site water may be drained back into the original body of water, as long as conditions are such that this would not cause chemical or biological contamination. Otherwise, such water must be drained into a suitable container for treatment prior to final disposal.

• If water is drained and collected, it must be disinfected and then disposed of by suitable means to avoid causing environmental damage or contamination.

• After draining contained water, all compartments should be filled with a disinfecting solution, and whenever feasible, the disinfectant should be retained in the compartment until arrival at the next site.

• If the compartment is too large to make filling practical, rinse it thoroughly with a disinfecting solution, and repeat.

   

  Boat hull surfaces, anchors, and trailers:

• Option 1: All surfaces must be scrubbed to remove any clinging material from the field site, then visually inspected and any remaining field site material removed, and finally hosed down with hot and/or high pressure water.

• Option 2: All boats, anchors, trailers used in field sampling will be cleaned using a self-service automatic car wash.

• Option 3: A boat hull, anchor, or trailer will be assumed to be free of live mussels if it has been thoroughly scrubbed, visually inspected, any visible field site material removed, and has remained dry and out of the water for at least 2 weeks (or 1 week in dry weather > 20 ºC.

  Regardless of which option is used for cleaning, visual inspection must follow with special attention being paid to: 1) cracks and crevices in which mussels may become trapped, and 2) aquatic macrophytes harboring juvenile mussels that may be present on trailers or propellers. Particular attention must be paid to trailer pads made of carpet and foam rubber, which could trap tiny mussels. If possible, such material should be removed from trailers before doing work in zebra mussel-infested waters.

Acceptable methods for disinfection
 

Chemical disinfection: This depends on the concentration used and the contact time. Since adult zebra mussels can close up and survive for extended periods of time under toxic external conditions, chemical disinfecting as a means to kill adult mussels may require a contact time of several days. It must be confirmed that the solution chosen is 100-percent effective in killing live zebra mussels within the contact time adopted. This determination should be completed at the beginning of the proposed research, and documentation of the test method used and observations confirming mortality should be retained and made available upon request. Suitable procedures for solution, contact time, and life-stage effectiveness documented in peer-reviewed scientific literature may be adopted by reference without further testing.

Heat: Temperature and exposure time determine the effectiveness of temperature treatments. Live steam, autoclaving, or boiling are all believed to be 100-percent effective against all zebra mussel life stages, as well as potential parasites they may contain. Minimum exposure times of

3 min at full heat for individual mussels and 10 min for clusters are recommended.

Freezing: Adult zebra mussels have a relatively low tolerance to freezing. Clarke et al. (1993) reported 100-percent mortality when individual mussels were exposed to -10 ºC for as little as 1.3 hr. However, clusters of mussels were more tolerant than individuals and the corresponding freezing mortality exposure time at -10 ºC appears to be at least 4 hr.

Physical: Crushing is an effective way to kill adult mussels, but may not be effective against attached larval or juvenile stages. Therefore, crushed adult remains should also be exposed to a chemical disinfectant solution prior to final disposal.

Desiccation: Desiccation is effective if allowed to continue for a long enough period of time. There are reports that live adult zebra mussels have survived for up to 21 days out of water under ideal conditions in a controlled laboratory setting. However, complete desiccation and exposure to warm dry air and/or direct sunlight should be effective in a week or less, but must be confirmed.

Approximate concentrations and contact times necessary to kill zebra mussels are presented below. The guidelines presented in the table are believed to be adequate to obtain 100-percent mortality for the veliger stage and may also be adequate for the other life stages, including juvenile and adult mussels. However, researchers are advised to test whichever procedures(s) they decide to use to assure 100% mortality. The use of lower concentrations or shorter contact times must be justified by experimental results conducted by the researchers.

Slowing the Spread of the Zebra Mussel Contents

Protocol for Responsible Monitoring Procedures