The predatory Dikerogammarus villosus can have serious impacts on the ecology of habitats it invades and can cause extinctions, the BBC reported.
Dubbed the killer shrimp by biologists for its voracious appetite, it often kills its prey and leaves it uneaten.
Originally from the steppe region between the Black Sea and the Caspian Sea, D. villosus, which can grow to be much larger than native freshwater shrimp, has been spreading across Western Europe for 10 years.
Already found in a Britain in September, Welsh environmental authorities confirm it has been found in Cardiff Bay and a reservoir near Port Talbot.
"Despite the fearsome name, these are not a threat to people, but the damage they can cause to our environment here in Wales is a very real danger," Environment Agency Wales Director Chris Mills said.
"Because of what they eat and the rate that they eat it, it can alter the food chain and our ecosystem by increasing the competition for food, and the native species that rely on the insects could go elsewhere," he said.
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