Sep 18, 2007 — The Clayton Opera House was an appropriate setting for a state Assembly hearing on invasive species yesterday. The St. Lawrence River outside hosts zebra and quagga mussels, round gobies, and the fish-killing disease, VHS, some of the best-known invasives. They've caused billions of dollars in economic and ecological damage. And many hitchhiked here in the ballast of foreign freighters that float past Clayton every day. Experts testified that the federal government has dropped the ball on stopping the spread of invasives. But they said New York could be in a unique position to take a stand. David Sommerstein reports.