Four months after they put down an acre of rubber mats in the lake's southeast corner, scientists have looked under the mats.

"We pulled all the mats up and yeah the Asian Clam are toast."

UC Davis researcher Marion Wittmann says the dime-sized clam poses a threat because it fosters algae growth, not only hurting water quality but killing native species.

Whittmann told Capital Public Radio's Insight the mats are a non-chemical way of depriving the clams of oxygen.

"If a clam doesn't have oxygen then it cannot live."

The downside is that some native species are dying as well. Whittmann says they have a small army of researchers analyzing samples collected under the mats...

"…and see really what's there and what's still alive and what's not alive. So that's going to take a little bit of time."

Scientists say the Asian clams may have come to Lake Tahoe as peopled dumped the contents of their home aquariums into the lake.