They're here.

Hundreds of Prussian carp — a female fish that can replicate itself using sperm from other species — have been found in Saskatchewan waters.

Prussian carp are an aquatic invasive species in Canada in the same genus as goldfish.

Their reproductive process, called gynogenesis, has made them prolific breeders.

"That's a fancy word to say that they've done away with males," said Chris Somers, who is a biology professor at the University of Regina and part of the Saskatchewan Sportfish Research Group.

The male DNA isn't actually incorporated into the offspring and all of the baby Prussian carp are clones of their mother, he said.

"They just sort of steal the sperm for a moment to stimulate division of the egg." The sperm is found floating around in rivers and lakes.

Mysterious arrival

Somers said the Prussian carp look like large goldfish, except for the gold colour, and eat plants, insects and other fish.

Prussian carp have been spotted sporadically in western Saskatchewan for the last few years but those were always one-off situations.

In May, hundreds of Prussian carp were found dead when the ice disappeared from Stockwell Lake.

"When you see hundreds of fish that are winter-killed, it usually means there's probably thousands that are actually out there."

The fish is typically found in Eastern Europe and Asia. They were first spotted in Alberta waters in the mid-2000s, Somers said.

The mysterious thing is that no one has been able to pinpoint how they got into prairie waters.

One theory is that one carp may have been mixed in with goldfish and was part of a "pet release," something Somers said people should refrain from doing.

Anglers asked not to release

The fish are about five or six pounds and grow to be about 35 centimetres long.

He said the fish are edible, but likely won't fit the North American palate.

Somers said the fish tend to take over the habitats they enter and edge out native species, so he asks people to kill the carp if they reel any in.

"If you do happen to catch one, we would ask that it be humanely destroyed rather than released back into the water."