Heidi L. Dunn, Ecological Specialists, Inc., 114 Algana Court, St. Peters, MO 63376

Abstract. Unionids are frequently relocated from construction sites to mitigate impacts, particularly to endangered species. However, past relocation monitoring has been minimal and data suggests low recovery and possibly survival of unionids following relocation. Additionally, construction impact areas are often based on anecdotal information and few studies have tested the adequacy of buffer zones around construction, barge spudding and mooring, and streambank disturbance. Another seldom considered issue is construction area recolonization and habitat enhancement. Unionids were relocated from eight construction areas in six different rivers between 1987 and 1997. Monitoring varied among relocation studies from one to ten years, and frequently included monitoring of relocated and resident unionids. Factors contributing to high recovery and survival include using field personnel familiar with unionids, selecting a relocation area with a stable substrate and a similar unionid community that is near the collection area, keeping animals moist or in water, and avoiding extreme temperatures and overcrowding. Unionids within construction/demolition areas were monitored in two studies. Unionids were affected by construction up to 5 m from cofferdams and by pier demolition up to 16 m from piers. Methods of enhancing unionid habitat during construction were considered in two construction projects. Substrate was stable one year after relocation, and a few unionids had recolonized construction areas. Future mitigation of construction projects needs to include evaluation of buffer zones and habitat enhancement, as well as, survival of relocated unionids.