The signal crayfish – Pacifastacus leniusculus – is invading non-native habitats and killing off indigenous species. It’s immune to a fungus disease that threatens other crayfish. It can act as a disease carrier. It will fight for shelter and food and even eat its own kind…
This crayfish species was first brought over from California to Europe in 1960 after a fungal plague killed off most of the indigenous species. But since that time, alien Pacifastacus has worked its way across Europe through water ways, invading habitats all the way to Asia. Some reports suggest that this crayfish species can live up to 20 years in the wild and grow to 16-18cm in size.
According to biologist Dr. Carin Bondar, a Vancouver-based crayfish expert, “there are two major reasons why Pacifastacus is such a successful invader: First, the fungus that causes the crayfish plague – Aphanomyces astaci – has caused enormous die-offs of species endemic to Europe and other parts of the world. Not only is Pacifastacus immune to this fungal disease, it also acts as a vector of it! The fungus can be carried on the cuticle of Pacifastacus to new environments, where it wreaks havoc on native species. Second, Pacifastacus is one of the most aggressive crayfish species, so even in areas where the fungus is not present, it is likely able to fight off native species for food and/or shelter. It will also directly kill and consume other species [and its own].”
And while Pacifastacus is invading habitats across the world, Dr. Bondar shares that “many North American crayfish species are actually in danger of extinction.” A recent report on the signal crayfish states that “it may exert a significant grazing pressure on macrophytes, aquatic insects, snails, benthic fishes and amphibian larvae.”
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Photo Credit: Carin Bondar, Ph.D