Une station d'écrevisses à pieds blancs : Austropotamobius pallipes Lere. (Decapoda -Astacidae) en zone périurbaine

A population of Austropotamobius pallipes, Lere., likely acclimatized has been living since many years in a gravel pit and in the flowing out brook, very near a city and in an unfavourable mountain climate. In the lake crayfishes reach a bigger size than in the brook. In summer time they live along the shore. In the brook the density of population is swiftly decreasing downstream ; the size of the animals is also decreasing and females do prefer the vicinity of the outlet of the lake ; shelters on the left bank could explain this behaviour. Downstream, junction with another brook brings chemical modifications, especially in calcium content and some pollution from domestic sewages that strike out crayfish. Runoff coming from an adjacent road and lack of hiding places in the banks could also be responsible for the disappearance of crayfish. Size frequency histograms give the length of animals according to the age for their first years of life. Reproduction cycle occupies three quarters of the time in a year for the adult females. In spite of unfavourable climatic conditions growth is normal in comparaison with animals living in more favourable regions. Health condition in the population is excellent. There is no fishing exploitation at this moment. Such a biotope could provide valuable adult crayfish for planting experiments. Crayfish formerly very abundant in Haute-Savoie becomes now scarce to a dangerous level and it could be advisable to set up some measures to restore populations of this interesting animal.