Berlin - Alongside the red American swamp crayfish, which has been terrorising Berlin lakes and waterways for years, the marbled crayfish - a popular pet - is also on the rise in Berlin and is threatening native flora and fauna. The marbled crayfish, originally from North America, is also an invasive species and has morphed from harmless aquarium dweller into a feared underwater omnivore. Procambarus virginalis, as it's also known, has spread to the wild over the past two decades, not least because anglers have used it as live bait. Or it was simply abandoned, even just flushed down the toilet? At any rate, the marbled crayfish has made Berlin its home.

Marbled crayfish in Lake Grunewald and Lake Groß Glienicke

The animals, which are usually twelve centimetres long, threaten native crayfish species not only because of competition for food, but because they are carriers of the crayfish plague. To counter this deadly threat, marble crayfish are now to be fished in Berlin for the first time. The season officially began in April, but Derk Ehlert, a wildlife expert at Berlin's environment department, says the quantities are not yet significant because of the cool temperatures. That could soon change: The marbled crayfish live in Grunewaldsee and Groß Glienicker See, but it remains to be seen in what quantities - they're still relatively inactive.

Another voracious invader: the red American swamp crayfish (Procambarus clarkii).
dpa/Britta Pedersen
Another voracious invader: the red American swamp crayfish (Procambarus clarkii).

Over the past three years, Berlin has been deliberately culling red American swamp crayfish populations - between 0.9 and 1.3 tonnes per year - with some eateries cooking up the catch. The fisherman who has been catching the crayfish so far will also be setting the traps for the marbled crayfish. According to Ehlert, a total of five invasive crustacean species have been identified in Berlin's waters. These include the spinycheek crayfish, the Galician marsh crayfish and the mitten crab. Swamp and marbled crayfish are the most problematic species and are therefore also targeted for capture, Ehlert said.

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