The other day I got the opportunity to join a friend who is a professional diver and marine biologist on one of his assignments. The task was to dive a local limestone quarry to assess the crayfish population. In Sweden there are two species of crayfish, the naturally occurring species Noble Crayfish (Astacus astacus, flodkräfta in Swedish, left image) and the signal crayfish (Pacifastacus leniusculus, right image) which has been imported.
Since the imported signal crayfish is a carrier of the crayfish plague to which the noble crayfish is highly sensitive, efforts are made to eradicate the signal crayfish from private fishing waters, as in the case of the quarry in question. The purpose of our dive therefore was to assess the crayfish population to see how many of the unwanted signal crayfish remained in the quarry.
Nitroxxed 