European elvers -- the eel in their juvenile state -- are threatened with extinction, in part due to poachers hoping to make a killing by flogging them off to eel-ravenous buyers in Asia.

Estimating the harm caused at a minimum of 476,000 euros ($515,000), authorities said the illegal eel-smuggling ring in the Vendee and Charente-Maritime regions was dismantled in a "vast judicial operation" on Tuesday.

"Several fishing professionals are suspected of having organised a clandestine export network towards Spain, in violation of the regulations in force," said a joint communique from the justice ministry, the French biodiversity office, the police and the Central office for the fight against harms to the environment and public health.

It noted that elver-fishing was highly regulated in France, with quotas and restricted periods of the year.

Elvers for food usually sell for 400 euros per kilogramme in France. But poachers prize the migratory fish because it can go for between 2,000 and 6,000 euros per kilo to breeders in Asia, the joint statement said.

The authorities said that the bust resulted in tens of thousands of euros and five vehicles, including a Porsche, being seized as likely compensation for the assessed ecological damage.

The suspects were released after being processed,to be summonsed for trial at a later date, the biodiversity office said. If convicted, they face up to seven years in prison and fines of up to 750,000 euros.