A roundup of Asian carp on Kentucky Lake using 1,000-foot-long (305 meters) nets is opening a new front in a 15-year battle to halt their advance. The invasive fish threaten to upend aquatic ecosystems, starve out native fish and wipe out endangered mussel and snail populations along the Mississippi River and dozens of tributaries. According to data compiled by The Associated Press, state and federal agencies together have spent roughly $607 million to stop them since 2004. Until recently most of the effort was focused on keeping them out of the Great Lakes. Now Southern states are becoming more active. Projects in the works are expected to push the price tag to about $1.5 billion over the next decade.