V. Effects Analysis


Effects of Actions on Species and Designated Critical Habitats


The implementation of a dreissenid control action is intended to benefit CRB native fish and wildlife species long term. In general, ephemeral effects are expected to last for hours or days, short-term effects are expected to last for weeks, and long-term effects are expected to last for months, years or decades. The activities covered by this program may have some ephemeral or minor, unavoidable, short-term adverse physical effects, such as increased sedimentation or riparian disturbance, to achieve dreissenid eradication. Minimization measures, such as best management practices, have been incorporated into the proposed action to reduce these short-term effects. However, short-term adverse effects are reasonably certain to occur, and are generally associated with near- and in-water application of chemicals or biocides. The direct physical and chemical effects of each project will vary depending on the type of action being performed. The effects to habitat that are common to many of the activity categories are discussed first, followed by a discussion of habitat effects specific to each activity category.


Effects to the Environment


Dreissenid control actions are intended to have long-term beneficial effects to the habitat of listed fish species at a variety of scales through removal of dreissenids that causes widespread, deleterious and long-term ecosystem effects through the physical and chemical alteration of any ecosystem in which they are introduced. Once established, Dreissenid mussels can dramatically alter the ecology of a water body and associated fish and wildlife populations. As filter feeders, they remove phytoplankton and other particles from the water column and thus shift production from the pelagic to the benthic portion of the water column (Sousa et al. 2009). Native mussels are significantly threatened by the presence of invasive mussels. By attaching themselves to the surfaces of other bivalves, Dreissenid mussels can starve freshwater mussels and drive indigenous populations to local extinction. Dreissenid mussels can also affect dissolved oxygen through respiration, and dissolved calcium carbonate concentrations through shell building (Strayer 2009).


Dreissenid mussels can cause substantial economic damage by infesting municipal, industrial, and agricultural water systems and attaching themselves to the hard substrates of pipes, dams, and diversion pathways. This restricts the flow of water through the systems impacting component service life, system performance, and maintenance activities. The annual cost to power plants and municipal drinking water systems in North America has been estimated between $267 million and $1 billion dollars (Pimental et al. 2005, Connelly et al. 2007).


Dreissenid eradication will have benefits at the project site, watershed, state and regional scales. Proposed actions will include activities that result in short-term adverse effects to habitat.

  1. The direct effects of control actions typically begin with pre-control activities, such as surveying, placement of barriers, and minor movements of equipment and personnel within the action area. Examples of effects associated with these activities may include increased sedimentation, increase in water temperature in the area enclosed by the barriers, and loss of riparian vegetation.
  2. The next stage, site preparation, typically requires construction staging areas, and materials storage areas that affect more of the project area. Effects associated with these activities depend on the type of control action proposed (e.g., reservoir drawdown versus biocide application) and the location of each activity, and will be analyzed in subsequent sections.
  3. The third stage, control activities, may introduce a chemical, biocide or other product to the environment. The duration of physical changes to the environment, which will occur with any control activity, will depend on the type of control action taken.
  4. The final stage for control actions is site restoration, which is intended to restore ecological function and habitat-forming processes to maintain or promote the site along a trajectory toward conditions that support functional aquatic habitats. This stage also includes long-term monitoring to assess the existence and status of dreissenids, effects on non-target organisms, physical changes to the environment, and effectiveness of site restoration activities.