Asian gudgeon bring new terror to rivers

February 9, 2016

Small in size but significant in terms of the ecological and economic damage they cause, Asian gudgeon are invading a great number of water courses across the world, particularly in Europe. These fish carry a half-animal/half-fungal parasite, which has very likely been present in China for millions of years and which is fatal to most other fish species. Having discovered this pathogen 10 years ago, IRD researchers and their partners have recently demonstrated how quickly it can spread in a Turkish catchment area. Three years after the arrival of the gudgeon, between 80 and 90% of fish were contaminated, including farmed bass, a species of great economic importance in the Mediterranean.

Arriving from China 50 years ago, a small fresh water fish from the carp family, known as the 'Asian gudgeon', has since caused devastation in the rivers of Europe and North Africa. This creature has successfully colonised various aquatic environments due to its highly efficient strategy for reproduction. But most importantly, as demonstrated in a study by the IRD and its partners, published in Emerging Microbes and Infections (Nature), it is propagating a devastating mycosis, a cousin of the well-known chytrid fungus, which has decimated frogs and toads throughout the world over the last few decades.

A parasite from another age

This small invasive fish is the healthy carrier of a parasite named Sphaerothecum destruens, bordering between the animal and fungal kingdoms. This organism, the type of which was only discovered recently, emerged several million years ago when animals and fungi became differentiated. The research team discovered this parasite in the Asian gudgeon in 2005 and subsequently observed its damaging effects on other fish species under laboratory conditions.

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