Benthic survey of Ellisport Bay, Lake Pend Oreille, Idaho, for Asian clams

Background/Question/Methods

Native to freshwater lakes and streams in Asia, the Asian clam (Corbicula fluminea) was introduced to North America in the early 20^th century. This species can influence native mollusk communities, alter water quality, and change food web structure.    Asian clam infestations in lakes are documented to create conditions that support unsightly algal blooms, and litter the shore with shells.  In rivers, the Asian clam causes biofouling in waste water treatment plants, power plants, and other intake structures.     A small population of Asian clams was first discovered in 2012 in Ellisport Bay in Lake Pend Oreille, Idaho near a resort community. The objectives of our study were to determine the extent of the distribution of Asian clams in this bay, to determine the environmental characteristics associated with their occurrence, and to consider potential management options. In the summer of 2014, over 200 Ponar grab samples were removed from the substrate along a grid throughout the bay.  The location and sediment characteristics were evaluated and recorded along with the presence or absence of Asian clams.

Results/Conclusions

We found native clam species scattered throughout the area, but Asian clams were found only in the sand and cobble areas close to the shore near the resorts.  Although management recommendations such as cleaning, draining, and drying all recreational equipment after use are important to reduce the spread of this invasive species, other management efforts are being explored.  At the end of the summer we elected to pursue a control strategy using a non-permeable benthic barrier placed over the infested area. This approach was modified after measures used successfully to control a larger infestation of Asian clams in Lake Tahoe, CA/NV.