Mussel Relocation Protocol

This protocol was developed by the Department of Natural Resources for relocating native mussels out of harm’s way from areas of potential in-stream impacts.

Relocations will occur in a time frame that allows completion of all relocation work prior to the initiation of activities that impact the streambed. This is to ensure that mussels do not move back into the relocation area before construction is initiated. The relocation schedule may be modified to occur in advance of project activities if mussels are not expected to move into the impact area (i.e. mussel moved in the late fall for activity starting in early spring). To minimize the thermal stress to the mussels, water temperature should be above 40℉.

Relocation Personnel

A malacologist experienced in unionid collection and monitoring techniques will coordinate collection and relocation efforts, and monitoring if required. The malacologist must be familiar with the identification of Wisconsin unionid mussel fauna and have particular expertise in the identification of rare species. The malacologist will be part of the relocation team.

The relocation team is responsible for collection and relocation efforts, and monitoring if required. The team provides personnel and equipment needed to complete all activities according to this protocol, and the team is responsible for acquiring all state, federal or other permits necessary for handling mussels at the site. Sufficient staff must be available to ensure safety and quality of work and minimize stress to the mussels during all phases of the relocation effort. The relocation team will prepare a final report following the relocation effort.

Transplant Area

Prior to the relocation effort, the relocation team will select a suitable transplant site. The site must be approved by NHC staff and should:

1. Be close to the collection area with sufficient habitat to support a viable population.
2. Have similar or better water quality, substrate, and fish fauna to the collection site
3. Not be influenced by factors detrimental to unionids (e.g. point discharge, dredging, navigation)
4. Have an existing or historical mussel population with similar species composition
5. If required, samples may be collected within the transplant site to determine existing unionid density and substrate composition before relocating. Mussels collected during sampling will be returned to the transplant area.
6. NHC staff will coordinate if there are problems determining a suitable transplant site.

Impact Area

Impact Area Delineation

Mussels will be relocated from all areas of temporary or permanent in-stream impact. If the impact is a bridge, the new bridge structure and any temporary structures used to construct the bridge (i.e. causeways, temporary bridge, barging staging areas) should be considered in the area of impact. All impact areas should include an appropriate buffer as dictated by substrate and flow conditions at that site. The impact area should be clearly marked, and the markers will remain in place throughout the relocation effort. If required, markers will remain in place throughout all in-stream construction activities and activities will be limited to these areas. This is to ensure that impacts to the streambed are contained within the areas where mussels were removed. The appropriate state or federal natural resource agency will determine whether the markers remain in place and should review any changes in construction plans and modify the impact area prior to the start or continuation of any work.

Mussel Collection from the Impact Area

Following the delineation of the impact area, the relocation team will establish transects or a grid within the collection area. All mussels in the impact area will be collected. Collecting from downstream to upstream is recommended as the most efficient approach. All mussels will be collected into mesh bags that will be maintained in the water. The number of mussels collected in each bag will be based on the size and number of mussels and adjusted to avoid overcrowding. All areas will be traversed at least twice to ensure all or an acceptable percentage of the total number of mussels within the area are collected.

Holding, Processing and Transport of Mussels

Following the collection of mussels from the substrate, the mussels will be maintained in the water at ambient temperature during holding and subsequent transport to the relocation site. Out of water time during processing should be kept to the minimum required to identify and process. Water temperatures should be monitored throughout the relocation. At a minimum, all mussels collected will be identified, counted, and relocated. Mussels may also be measured, aged and marked if required. All listed species will be identified, sexed (if appropriate), measured, aged, and uniquely marked on both valves. The gravidity of females should be noted (if appropriate and conducted cautiously). The method to be used for marking mussels should limit handling, be accomplished with a minimum out of water time, be fairly permanent, match shell type and size, and be easily readable after several years.

Placement of Mussels at Transplant Site

All listed species will be hand placed in a natural position within the substrate. The remaining mussels may be distributed by hand along the surface of the substrate, from the surface of the water above a suitable substrate, or hand placed in the substrate. Mussels should be distributed evenly (by boat, diver, or wading) in suitable habitat. An initial swim over is required at the completion of the relocation efforts to make sure mussels are distributed evenly and to collect any fresh dead from initial mortality.

Monitoring

Monitoring may be required to evaluate the success of the relocation project. Personnel from the relocation team will be responsible for conducting all monitoring unless other agents are agreed upon. Collected mussels will be identified and replaced. Listed species collected during the monitoring effort will be returned to the location where they were collected at that time. The dead shell of any species will be collected and reported, and its deposition determined by NHC. If calculated, the mortality of relocated listed species will be compared with mortality of other relocated and resident mussels. One-month monitoring may be required if there is a concern for immediate survival or other factors, but may not be required in waters lacking adequate visibility to avoid excessive handling of recently transplanted mussels. Yearly and subsequent monitoring may be required depending on the type of project, species involved and sensitivity of the resource, and would include a cursory search outside the relocation area to recover shells that may have been displaced and observe mussels that may have moved. General condition and behavior of the relocated and resident mussels should be noted.

Reports

A report will be prepared by the relocation team following completion of the relocation, detailing methods, data from relocated mussels and data from the transplant site. Additional monitoring reports will be submitted if required.