Broadscale distribution, abundance, and habitat association of the Asian clam (Corbicula fluminea) in the lower Columbia River, USA

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Salvador Robb-Chavez, Washington State University Vancouver, Washington State University, Vancouver, WA, Stephen M. Bollens and Gretchen Rollwagen-Bollens, School of Biological Sciences, Washington State University, Vancouver, WA, Stephen M. Bollens, School of the Environment, Washington State University, Vancouver, WA, Gretchen Rollwagen-Bollens, School of the Environment, Washington State University, WA

Background/Question/Methods
The Asian clam, Corbicula fluminea, is an invasive freshwater bivalve that has established populations throughout the globe, including the Pacific Northwest, USA, and is known to have deleterious effects on natural and human systems. During 2017-2020 we collected adult and juvenile C. fluminea from 15 mid-channel and 29 shore-based sampling locations spanning 537 rkm of the Columbia River (CR) to elucidate the association of C. fluminea abundance and condition with habitat characteristics including dissolved O2, pH, temperature, salinity, specific conductivity, depth, geographic location, chlorophyll a concentration, bank slope, and sediment composition (granulometry, TOC). Triplicate samples were taken at 5m intervals at 30 cm water depth at shore-based sites, with all C. fluminea individuals >2 mm shell length within a 1 m2 quadrat collected from the top 15 cm of substrate, alongside surface water/sediment samples and environmental recordings. Mid-channel shipboard sampling utilized a Ponar grab sampler deployed at depths of 4-27 m to collect C. fluminea and sediment samples in tandem with surface water samples and environmental recordings.
Results/Conclusions
C. fluminea abundance was greatest at the confluence of the Sandy River with the CR near Gresham, OR (avg. 342 ind. m-2), with the majority of sample sites with abundances >100 ind. m-2 located downstream of Bonneville Dam and the majority of sample sites with abundances <100 ind. m-2 located upstream. Our results provide a better understanding of the basic biology and ecology of this global invader, as well as provide natural resource managers with information on where, when, and why this bivalve invades temperate river ecosystems.