Asian carp DNA has been found in Lake Michigan for the first time, raising fears that they could devastate the Great Lakes' delicate ecology - and commercial fishing interests, of course.
The announcement was made just hours after the Supreme Court rejected a request from Michigan to force Illinois to block its waterways from flowing into the lake.
No actual fish have been spotted north of electric barriers near Romeoville. This has led some observers to suggest that the DNA could have come from carp used as a fisherman's bait - or even from a resident's poo (many nationalities eat carp at Christmas).
But Michigan isn't to be fobbed off.
"Today's announcement that DNA evidence of Asian carp has been found past the so-called electrical barrier and even the locks is frightening. Michigan residents are outraged that President Obama's administration and Illinois officials refuse to take immediate action despite continued evidence of an immediate threat," said Michigan Attorney General Mike Cox.
"I applaud the governor for renewing our request of last week to meet with President Obama to address this looming crisis for the Great Lakes."
The species has been steadily invading North America since escaping from government hatcheries in the 1970s and since. They're a pretty impressive species, known for their ability to jump up to ten feet out of the water.
Carp are quite a delicacy in the Far East and in Eastern Europe, prompting calls to deal with the little blighters by eating them.
A group of companies in the Louisiana area is planning to market the fish to consumers - with the shiny new name 'silverfin'.