There are 250 different species of native crayfish in North America, 110 in Australia and only seven in Europe. The species Astacus astacus is native to Scandinavia; 10,000-year old fossilized specimens have been discovered in the area. The first documentation concerning the consumption of this crustacean dates back to the late Middle Ages, when it became popular among Swedish nobles. By the 17th and 18th centuries crayfish consumption had spread to all the classes, as it was inexpensive, plentiful, and easy to fish in any of the country’s lakes and rivers. The Swedish native crayfish, Astacus astacus, lives symbiotically in the waters in which it flourishes. In the autumn these crayfish are fished with special crayfish traps. After a quick sorting procedure, they are either transported alive to the market places or they are cooked. But there are also a handful of aquaculture farms in Sweden that raise this native crayfish. The farming is an intensive form of aquaculture, where the crayfish live in man-made ponds. Sometimes they are sorted out for size and sex during the period of growth, which can be 2 to 5 years. In very intensive farming the crayfish are kept in ponds without any other fish. More intensive farms may sort the crayfish more often. The crayfish are also fed during the growth period and no chemicals, drugs, medicaments or nutrients are added. In one classical preparation, crayfish are boiled with dried head dills. This dish is fundamental to the dinners that traditionally take place at the end of summer (kräftskiva). During the 1960s a parasitical fungus devastated the Finnish crayfish population; while always present in Scandinavian waters, its prevalence grew with the importation of crayfish from the States. In subsequent years the importation of the American Pacifastacus leniusculus considerably increased to satisfy the growing demand, marking the end of Astacus astacus. The fishing and selling season runs from the beginning of August until mid-September, when the species reaches full sexual maturity and eggs have already been layed. Native species still exist in some isolated areas in Southern and Central Sweden, far away from crayfish hatcheries of American species, and are raised as well on other small hatcheries on the Öland and Gotland Islands and in the Småland and Blekinge Regions.