Toronto

The flathead catfish, a large North American fish that can reach up to 120 pounds, has established itself in waterways beyond its native range, including parts of Canada. 

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The conservationists are sounding the alarm about their expansion across the country from their original habitat in the Gulf of Mexico basin.

'These fishes are going to be one of the apex predators around every system once they establish those populations,' said biologist Joel Fleming.

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The catfish that lays around 10,000 eggs at a time, was once restricted to the rivers of the south, but now has spread across the country. This expansion is attributed to two factors, intentional introduction into new waterways and the fish's natural tendency to move from crowded habitats.

The flathead catfish were detected in California in 1962, Virginia in 1965 and the Potomac in DC in 2003.

Notably, they get heavier the longer they are established with a 66lb example breaking the state record in Pennsylvania in June last year.

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According to scientists, global warning has contributed to their stretch which has now reached the Thames River in southern Ontario.

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Scientists are concerned that flathead catfish may have formed a self-sustaining population within the river. This is particularly concerning as the river already supports 25 fish and mussel species classified as at-risk.

According to biology professor Nicholas Mandrak of the University of Toronto who is an expert in invasive fish species, “Any one fish is going to be eating kilograms and kilograms of fish every day.”

“I think that very likely climate change is part of it,” he told CBC and added, “As our waters warm, they become a more appropriate temperature for these southern catfishes to survive in Canada.”

Mandrake further said, “They get very large and they eat a lot of fishes, so they're likely to have a substantial negative impact if we do not do anything to control their populations.”

Conservationists in Georgia caught and removed 64,000 in nine years after they established themselves in the state's Satilla River, but admit they are fighting a losing battle. 

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Scientists in Ontario are now considering how to deal with the southern invasion, but Tim Barrett of the Department of Natural Resources fears they may be wasting their time.

'It's just physically impossible to take them all out,' he said.

(With inputs from agencies)