Over the next week, the rotting carcasses of about 300 bighead carp surfaced. The smallest were 20 pounds. The big ones were a border collie-sized 35 pounds. Poisoned Asian carp, Chapman explained, are different from many fish species in that they typically don't surface unless the water is warm enough for gases to build up in their bellies, a process that can take a week.

"It was quite amazing there could be that much poundage in one small pond," Chapman said.

It turned out that a decade earlier the previous property owner had stocked the pond with bighead. They had flourished right under the nose of the new owner, who had smelled trouble - but couldn't see a thing.