Asian carp, reviled as the vanquishers of native aquatic species and seen posing a huge ecological threat, have somehow found their way into Lake Ontario.

Two male fish, both fertile, were discovered this week in contained ponds at Tommy Thompson Park near Toronto’s waterfront. One fish, over a metre long and weighing almost 40 pounds, was found Monday. The second one, a bit smaller, was caught Tuesday.

However, a federal official cautioned this is not an invasion.

“No one should panic. I’m not panicking. There is no evidence that there is an invasion. We are dealing with just two fish,” said Becky Cudmore, the Asian carp program manager at the Canada Centre for Inland Waters, a laboratory run by Fisheries and Oceans Canada in Burlington.

If there are any other carp in the area, they will be found, Cudmore said.

The two fish have been identified as grass carp, which belong to the Asian carp family. These invasive bottom-feeders, native to China, were introduced in the U.S. and Europe to tackle aquatic weeds. They have since infiltrated waterways throughout the Midwest to such an extent that they are now regarded as a serious threat to the Great Lakes.

If the carp, which feed on aquatic species, become established in these larger lakes, their constant eating will leave nothing for native species to eat, say scientists. Commercial and recreational fishing could be decimated and the lakes’ ecosystems devastated.

Experts warn the carp, which are spectacularly reproductive, could make previous invasive species, like the sea lampreys, look like a minor nuisance in comparison. Once an invasive species — fish or aquatic plants — gets into a body of water, it’s tough to eliminate completely.

This isn’t the first time that grass carp have been found in Ontario waterways: three live specimens have been caught in the Grand River near Lake Erie since 2012, when Fisheries and Oceans Canada started its Asian carp program. Those three were not fertile. (The program was started to prevent Asian carp from becoming established in the Great Lakes.)

Toronto and Region Conservation Authority officers found the local grass carp this week while doing routine work at a contained pond at the foot of the Leslie St. Spit. The pond was created about six months ago during construction work, said TRCA spokesperson Elizabeth Oakley.

The second carp was found at another pond nearby. It isn’t known yet where the two fish came from.

“We don’t know if they had been living in Canadian waters for a while or have come from the U.S.,” said Cudmore.

There is no evidence of any breeding or spawning behaviour, she said. “Those are all very good signs. But we are concerned and out there to find if there are any more.”

The two grass carp, now dead, will be sent to the U.S. for more tests.

No live specimens of silver carp and bighead carp — two Asian carp species that some U.S. experts warn are worse than grass carp — have been found in Canadian waterways since Oceans and Fisheries experts began their watch for Asian carp.

Cudmore said are all Asian carp species — which are prohibited in Ontario unless dead — are equally unwelcome in Canada, where there are no established populations. But that hasn’t stopped people from trying to smuggle them in.

Between 2005 and 2013, Ontario conservation officers, working with Canada Border Services agents, intercepted over 40,000 pounds of live Asian carp destined for Ontario markets at the border, said Jolanta Kowalski, a spokesperson with the Ministry of Natural Resources. Fines totalling $235,000 were levied in those cases.

Officers also issued fines totalling $105,500 in GTA markets where live Asian carp were found. There have been no seizures or charges since 2013, said Kowalski.

Meanwhile, staff from Oceans and Fisheries, the Natural Resources Ministry and TRCA in three boats will continue their hunt for Asian carp in the waters between Tommy Thompson Park and Toronto Harbour.

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“If there are any more, we want them out,” said Cudmore.

Four other species that could devastate the Great Lakes:

Northern snakehead

Native to eastern Asia, the northern snakehead is a voracious predator that lives in lakes, ponds and rivers. This fish has no natural enemies in North America and eats zooplankton, fish and fish larvae, frogs and toads, insects, small reptiles and sometimes even tiny birds. Northern snakehead can live out of water and wriggle around for a few hours while pursuing prey or looking for a new home.

In the U.S., where it has invaded some states, the species are also called “frankenfish.”

Wels catfish

Native to Europe, the Wels catfish can grow to as much as three metres long and weigh more than 200 pounds. They eat other fish — even birds — and they have long a lifespan, sometimes living up to 50 years. Found usually in the Baltic, Caspian and Black seas, the female of this species can release up to 150,000 eggs in two years.

Scientists say that if the Wels catfish show up in our waters, they would quickly become the top predator.

Silver carp

Like the other Asian carp species, silver carp were brought from Asia to North America in the 1970s. They have since migrated north through U.S. rivers, like the Mississippi, toward the Great Lakes. Silver carp eat huge amounts of plankton, thus competing for food with native organisms like mussels and larval fishes. They can weigh up to 60 pounds.

Silver carp are also called the “flying carp” because they can jump up to three metres out of water when disturbed by sounds of watercraft.

Bighead carp

Like silver carp, bighead are also known to be highly destructive. Introduced to the U.S. in the 1970s to improve water quality in sewage treatment plants, they have since infested much of the Mississippi River basin and are threatening to get into the Great Lakes through waterways. Like silver carp, bighead also compete for food with planktivores.

Unlike their cousins, they do not jump from the water and can be found on the surface of the water.

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