State officials have long maintained that there were originally just two snakeheads - a male and female - dumped in the pond two years ago by a local man when they outgrew his aquarium.
A federal expert in Florida identified a photo e-mailed from the DNR on June 17. Two weeks later, local angler Joe Gillespie turned in a 26-inch fish and said he had hooked one "the size of a golf bag" in April.
No fish that size showed up yesterday.
"That's one piece of the puzzle that doesn't match up," Schwaab acknowledged. "It could be another species. But who knows? Nothing is certain about this."
The two smaller nearby ponds also were poisoned, but nothing floated to the surface.
By the end of the day, DNR biologists had collected more than 120 juvenile snakeheads. Today, they'll place in the pond small traps with sentinel fish - "the canaries in the coal mine," as Schwaab called them - to determine whether the poison dose was lethal and whether they missed any spots.
The poison will dissipate over the next week, and biologists will "electro-shock" the pond this fall to ensure that no snakeheads survived. They will jolt the water with electricity to stun any remaining fish and cause them to float to the surface.
Next spring, if the eradication effort worked, the state will fill the pond with fish from its hatcheries. "Obviously," said Schwaab, "we'll restock with naturally occurring species."
Staff writer Lynn Anderson contributed to this story.