Louisiana crayfish, this scourge which abounds in Gironde

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“Louisiana crawfish?” I see some more and more. » Laetitia is categorical on this.

During a recent outing at Lake Saint-Michel, north-east of Bazas (Gironde), this experienced fisherman even carried out quite a raid. In her balance she caught around forty Louisiana crayfishbaited… with sausage.

Louisiana crayfish, disastrous for local fauna and flora

“They really eat everything,” explains the person concerned. But for aquatic life, they are Really devastating. »

It has been a very long time since Louisiana crayfish invaded the Gironde. Rivers, lagoons, lakes… They are everywhere. “The damage to aquatic fauna and flora is very significant,” attests Jean Martin, technical manager at the Gironde fishing federation.

They devour fish, fish eggs, dig burrows several meters long; which weakens the banks

Another problem: Louisiana crayfish are healthy carriers of a fungus that causes ‘local’ white-clawed crayfish to die.

A population that continues to grow

A real scourge possessing “a higher reproductive strategy than native species”. Understand: in addition to causing countless damage, they see their population increases without common measure.

So how to overcome it? “Fortunately,” emphasizes Jean Martin, “ Louisiana crayfish has predators ; all large birds, otters, mink, foxes and predatory fish. But this is not enough to regulate its population. »

Formal obligation to kill Louisiana crayfish

Fishermen are invited to participate in the war effort. “There are no quotas or dates for Louisiana crayfish fishing,” continues the technical manager. You just need to have a fishing license. Each fisherman can use up to 6 scales; the maximum diameter of the scales is 30cm, with minimum mesh size of 10mm. »

And, importantly, it is prohibited from transporting these live crustaceans. “They must absolutely be killed on the spot,” insists Jean Martin.

Signal crayfish captured near Grignols

But, as Jacques Chirac said, “the troubles always fly in squadrons”… And a new species is in the process of colonizing the territory.

His name: Signal crayfishmore commonly called California crayfish.

Last June, the fishing federation reported that during its fish inventories, “Signal crayfish were caught on the Lisos near Grignols. This invasive exotic species can measure more than 15cm! “

Already seen, among others, on the Ciron, in 2019, the Dropt in 2021, the Signal crayfish also represents “a real scourge” and “participates in the fall of plant and animal biodiversity”.

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