Lake Tahoe boaters beware: Asian clam control project at Emerald Bay

Boaters heading to Lake Tahoe in the next six weeks may experience a short delay when entering Emerald Bay due to an Asian clam control project that will be taking place there.
The Asian clam control project is being implemented by a team of partners from the Lake Tahoe Aquatic Invasive Species Program, with plans to treat an area of up to 5 acres at the mouth of Emerald Bay. Treatment will be accomplished by covering the infested lake bottom with thin rubber barriers, augmented with organic material, that reduce the available oxygen and smother the clams. It will be the largest project of its type in the history of Lake Tahoe.

The Asian clam control project is scheduled to begin on October 17 (weather permitting) and the deployment of bottom barriers will take from 4 to 6 weeks to complete. A TRPA boat will be on hand to help direct boat traffic in and out of Emerald Bay during the installation.

Boaters are advised to use extra caution when entering Emerald Bay during this period and to avoid endangering members of the dive team. Blue and white or red and white dive flags will be used by agency personnel to indicate that divers are in the water, at which point boaters are required to stay at least 200 feet away from the dive and project area. Boats entering or exiting Emerald Bay between the hours of 5 a.m. and 11 a.m. may be subject to short delays in order to ensure safe passage for the divers and control vessels.

"This is a physically demanding undertaking. The project team is laying down over 4 miles of barriers, in very cold water at the mouth of Emerald Bay where water currents are known to fluctuate rapidly,” said Dr. Geoffrey Schladow, Director of the UC Davis Tahoe Environmental Research Center. “Boaters are urged to help the effort by keeping a safe distance and following the directions of the guide boat.”

The barriers will be left in place for approximately one year in order to achieve clam mortality. Crews will return for three weeks in the fall of 2013 to remove the barriers. Work will primarily occur during early morning and on weekdays, with no work occurring on the weekends or holidays in order to reduce boater inconvenience.

Currently, the clams live on a shallow, gravel sill approximately 15 feet below the surface that partially separates Emerald Bay from Lake Tahoe. The Asian clam infestation at Emerald Bay is in the early stages of invasion and currently small enough to manage through an effective prevention and control program. Recent scientific research has shown that the use of bottom barriers is effective at controlling Asian clam infestations in Lake Tahoe. Without treatment, the population can grow rapidly and become extremely difficult and expensive to control.

"The Tahoe Resource Conservation District is proud to be a part of this broad collaborative effort and do our part in preserving the beauty and majesty of Emerald Bay,” said Jim Brockett, AIS Control Project Coordinator with the Tahoe Resource Conservation District. “We urge boaters to be safe and observant as our divers deploy the clam-killing barriers that will help protect Lake Tahoe from this invasive species."

Controlling the Asian clam population in Lake Tahoe is critical as the clams have a variety of negative impacts. The clams could increase the potential for other species such as quagga mussels to establish in Lake Tahoe by increasing localized calcium concentrations. They also promote the growth of algae by releasing highly concentrated nutrients. Increases in algae impact the scenic beauty of the shoreline by changing the water color, reducing water quality, and washing rotting materials onto the beaches. Perhaps most significant, Asian clams compete with native animals for habitat and food, which causes a disruption in the food web. By treating the Emerald Bay infestation in the early stage, these impacts can be minimized or avoided. The treatment will also
help prevent the spread of these invasive clams to other areas of Lake Tahoe.

“Preserving the exceptional boating and recreation opportunities in Emerald Bay State Park is important to us,” said Dan Shaw, Environmental Scientist for the California Department of Parks and Recreation. “We are asking the boating community to exercise caution and a little patience when enjoying Emerald Bay for the next month.”

The Lahontan Regional Water Quality Control Board, U.S. Fish and Wildlife Service, California Department of Parks and Recreation, and the Tahoe Regional Planning Agency are leading the charge to control Asian clams in Emerald Bay. The U.S. Forest Service, Pacific Southwest Research Station is funding continued research on the invasive clam infestation to monitor the effectiveness of this control effort. The team of partners working on this project also includes staff from the Tahoe Resource Conservation District, California State Lands Commission, Nevada Division of State Lands, and researchers from the University of California Davis Tahoe Environmental Research Center and the University of Nevada Reno.

The Lake Tahoe Aquatic Invasive Species Program consists of 40 public and private partner organizations including federal, state and local jurisdictions, research partners, public utility districts, and private marinas. This Program provides leadership, direction and resources to fulfill its mission of prevention, detection and control of aquatic invasive species in the Lake Tahoe Basin.

— Writer Kristi Boosman is the Public Information Officer for the Tahoe Regional Planning Agency. She can be reached at (775) 589-5230 or kboosman@trpa.org.