Freshwater Mussel Habitat Construction and Creation – St. Louis District Army Corps of Engineers

Freshwater Mussel Habitat Construction and Creation. Literature Review for the St. Louis District Portions of the Mississippi and Illinois Rivers and Similar Habitats. Freshwater Mussel Habitat Construction Meeting, Scope of Work Development, and Implementation to Assess Mussel Habitat Value of Existing Structures in the St. Louis District Portions of the Mississippi River, Evaluation of Mussel Data with Respect to Hydraulic Characteristics, and Recommendations for Future River Training Structure Construction

2012 – 2018

St. Louis District Army Corps of Engineers currently uses several types of river training structures to improve navigation while also maintaining or improving habitat for fish and invertebrates. They were interested in determining if these river training structures could be modified to create mussel habitat. EcoAnalysts reviewed literature and interviewed researches with respect to mussel habitat studies and mussel habitat creation attempts. Unionid mussel studies within the last 10 years within the St. Louis District were also compiled in GIS. Information was assembled in a report describing current knowledge of mussel habitat, mussel habitat creation, mussel distribution within the St. Louis District, and potential ideas for modifying river training structures for mussels. EcoAnalysts then conducted a workshop with biologists from St. Paul, Rock Island, and St. Louis Districts, Illinois Department of Natural Resources, and Missouri Department of Conservation, as well as river hydrologists and engineers from the St. Louis District. The goal of the workshop was to educate river hydrologists and engineers with respect to freshwater mussels, educate biologists on river engineering and hydrology, and develop ideas on how river training structures could be used to create or enhance freshwater mussel communities. Ideas from the workshop were used to develop a sampling strategy for assessing habitat conditions at existing training structures and reference sites (existing mussel beds). Preliminary data from bathymetric and ADCP surveys conducted by the St. Louis District were used to develop polygons for mussel sampling at 2 reference and 5 structure sites. Mussel beds and areas without mussels were delineated, and quantitative samples were collected in a 3 random start systematic design within these polygons. Principal components analysis was used to determine if mussel assemblage metrics (MCAT metrics [density, species richness, recruitment, age distribution, sensitive/tolerant species, species and tribe evenness, % Lampsilini]) differed among sites with and without mussels. PCA factors were correlated with hydraulic metrics to determine what metrics were associated with mussel beds. Habitat characteristics important to mussel presence include slope (20 to 30%), substrate composition (avoiding interlocking rock), particle size (D50 greater than coarse sand), and substrate stability (shear stress/critical shear stress less than 1). These ideas could be applied to bankline revetment, the interior of chevron dikes, chevron dike legs, and areas downstream of MRSs.