KANSAS CITY, Mo. — The discovery of two juvenile black carp in a ditch connected to the Mississippi River in Missouri is the first, troubling sign that the invasive species is reproducing in the wild and becoming more of a threat to already-endangered mollusks and some native fish, scientists say.

While adult black carp have been found sporadically in the Mississippi, November’s discovery near Cape Girardeau of juvenile fish among the hundreds of fish caught showed the black carp population in the river is higher than scientists expected, Missouri Department of Conservation resource scientist Quinton Phelps said, and that there’s a “high probability” that more black carp were caught.

“Scientists really thought there were not enough adult black carp in the wild to find each other and reproduce,” Phelps said. “But what we found through this sampling is evidence there are enough to reproduce and those young are surviving to a point where we are collecting them.”