Berlin's huge Tiergarten park is crawling with a species of crayfish native to America's Deep South. The Louisiana crayfish – also known as the red swamp crawfish – can be found swimming in the park's ponds and scuttling across its paths.

Juergen Goette, responsible for the park's upkeep, said the invasive crustacean could have disastrous effects. "The crayfish is an omnivore. It feeds on practically everything that it finds, such as plants, fish spawn and frog spawn from native frogs. This could wipe out entire native species," Goette said.

"In addition to this, they also carry the so-called 'Crayfish Plague', which is a fungal disease against which they are immune, but can infect and kill any native crayfish that may be present."

Goette said attempts to catch the crayfish and give them to the Department of Fisheries to be disposed have begun and will continue in the next few weeks.

This is a good gesture, but more must be done, say the Nature and Biodiversity Conservation Union of Germany (NABU). Katrin Koch, a NABU nature protection officer, believes that they have acted too late and a more permanent solution to prevent spreading should be found. She speculated the crayfish are likely to have arrived in the lakes after private owners improperly tried to dispose of them. She appealed to owners to act responsibly and not simply discard any kind of animal in the wild.

"You always have to appeal to people to keep pets responsibly and not to simply discard them somewhere. This applies to mammals such as dogs and cats, which cannot just be dumped somewhere. This is just as true for aquatic animals: fish, turtles and also for these swamp crayfish," she said. "We are a bit surprised about what gets released into the wilderness from the aquarium trade."

The Louisiana crayfish (Procambarus clarkii) is native to northern Mexico and southern and southeastern United States and is featured on the European Commission's list of invasive alien species