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Goal: Sustain Our Nation’s Forests and Grasslands Invasive clams are associated with reduced growth of native mussels

Native freshwater mussels are disappearing rapidly, but the causes are poorly known. New research suggests that Asian Clams are a factor. Higher abundance of Asian clams was associated with lower growth of native mussels. The invasive clams have been present in North America since the 1960s, but their effects on native biota had not been well-studied.

A person’s hands holding a dozen small brown clams
In the Rockcastle River system of Kentucky, Asian clams were associated with slower mussel growth. Courtesy photo by Robyn Draheim, Center for Lakes and Reservoirs, Portland State University.

North America has the highest diversity of freshwater mussels on Earth, and, as filter feeders, mussels are integral components of stream ecosystems. Unfortunately, mussel populations have declined rapidly since the 1970s, and many streams have lost their entire mussel fauna. The causes of these declines are unknown, which hinders efforts to protect and restore mussel populations.

The invasive Asian Clam, Corbicula fluminea, arrived in eastern North America in the 1960s before the detrimental effects of invasive species were widely recognized. Consequently, its effects on mussels and other native biota remained largely unstudied. Researchers recently renewed attention on Asian Clams because the timing of their arrival coincides with the advent of mussel declines. The team studied 17 streams in the Daniel Boone National Forest in Kentucky, where mussel declines were blamed on coal mining. They placed 3-month-old mussels in streams for three months and measured their growth. They also measured water quality and Asian Clam abundance at each stream.

The study found no evidence of severe mining effects. Instead, it found that native mussel growth was conspicuously lower at sites where Asian Clams were abundant. This suggests that Asian Clams negatively affect native mussels, perhaps by competing with them for food. The research provides an important clue for understanding causes of mussel declines and prescribing management actions necessary to restore populations.

Principal Investigators
Wendell R. Haag, Research Fisheries Biologist
4155 - Center for Bottomland Hardwoods Research
Strategic Program Areas
Invasive Species
Resource Management and Use
Water, air, and soil
Wildlife and Fish
Abundance of an invasive bivalve, Corbicula fluminea, is negatively related to growth of freshwater mussels in the wild
CompassLive Article
Asian Clams and Native Mussel Growth
External Partners
Steven Price - University of Kentucky
Andrea Drayer - University of Kentucky
Drew White - University of Kentucky
Jacob Culp - Kentucky Division of Water
Monte McGregor - Kentucky Department of Fish and Wildlife Resources