Biology and Ecology

An Overview of the Asian Clam, Corbiculus Fluminea

A handful of C. fluminea. Source

Excellent at Invading

The Asian Clam is the most widespread, invasive mollusk in all of North America (5). They are r-strategists that demonstrate rapid growth as well as high reproductive rates and fecundicity (6). This aids in allowing them to aggressively expand their range. Because of this, restoration efforts and limitation management are quite difficult (1).
Asian clam populations can reach densities of up to 3000 clams/m² in ideal conditions (2). They gather nutrients by filter feeding and pedal feeding, allowing them to gather resources from many different sources. Their life expectancy ranges between 1-5 years, and they have up to two reproductive cycles per year (6). 

Threats

Native Species Displacement, Reduced Fitness

The expansion of this species is a huge threat to native mussel populations, as C. fluminea strongly outcompete native invertebrates (4,1). High densities of the Asian clam have been implicated in the decline of native unionids (4). Also, studies have found that there are positive correlations between clam density and mortality of juvenile mussels (8). Yeager et. Al found that treatments containing 8-32 clams per contained ecosystem experienced 100% mortaliy of unionids (8). Even juvenile unionids feel the cost of Asian clam presence: growth rates of juveniles in the containers with clams were significantly lower than those in control containers without Asian clams (8). These demonstrate that Asian clams at high densities can affect the survival and growth of other freshwater shellfish. This has serious implications for native bivalve and unionid species.

Increased Asian clam density led to up to 100% mortality of unionids in Yeager et. Al (1999).

Mussel height decreases with increased density of C. fluminea (Yeager et. Al 1999)

Ecosystem Altering

Asian clams have profoundly negative effects on the ecosystems that they encounter. This includes altering benthic habitats, introducing nutrients into aquatic systems, limiting phytoplankton, and destroying aesthetic values of beaches (1). Bivalve excrement causes eutrophication, which leads to increased algal blooms (2). Algal blooms can lead to hypoxia in the environment, which is responsible for killing many species by depleting the oxygen available in the water. They have negative impacts on aquatic ecosystems, ranging from decreasing phytoplankton abundance to altering the cycling of organic matter in sediments and shifting benthic biodiversity, especially impacting native bivalve species (Wittmann et. Al).

Algae growing in presence of C. fluminea in the naturally oligotrophic Lake Tahoe. Source

Explore this website to learn more about C. fluminea, its effect on Lake Tahoe's ecosystem and the US economy, and how you can help to further limit this invasive species from taking over freshwater closer to your home!