Harvesting an invasive bivalve in a large natural lake: species recovery and impacts on native benthic macroinvertebrate community structure in Lake Tahoe, USA.

The increasing dispersal and establishment of aquatic invasive species in natural freshwater ecosystems has led to efforts to remove non-native taxa and/or restore native species. An invasive bivalve, Asian clam (Corbicula fluminea), recently (2002) became established in a large, natural subalpine lake (Lake Tahoe, USA). In 2009, experimental efforts were undertaken to harvest C. fluminea from Lake Tahoe sediments using a manually operated suction dredge apparatus. Treatment and control plots were monitored for a 450 day period after dredging to observe target species (C. fluminea) and non-target macroinvertebrate recovery rates. A paired Before-After-Control Impact analysis was used to assess the short- and long-term impacts of suction dredging. Physical harvest resulted in short-term reductions of C. fluminea (1500 individuals m-2 before treatment to 60 individuals m-2 14 days after treatment) with significant disruption to benthic macroinvertebrate community structure. The impact to the target invasive species (C. fluminea) was present 450 days after treatment and community diversity (as represented by Simpson diversity index) did not recover after 1 year (365 days) in dredged sites. Certain non-target macroinvertebrate taxa (Chironomidae and native clam (Pisidium spp.)) increased in suction dredge plots to levels greater than before treatment or in control plot conditions at the end of the study period. Harvesting C. fluminea significantly reduced population densities for a period of 450 days after the removal. Recolonization rates of C. fluminea and non-target species over multiple reproductive seasons will determine the feasibility for this method as a long-term control strategy. Copyright © 2012 John Wiley & Sons, Ltd.