The development of crayfish culture in Sweden during the last decade

This paper describes the development of crayfish farming in Sweden since 1984 and is based on study visits to 18 farms and on replies to three types of questionnaires sent out to fishery officers and various crayfish farmers in each county. Five hundred licences have been granted for rearing either noble crayfish, Astacus asfacus, or signal crayfish, Pacifastacus leniusculus. The total quantity for which licences have been issued is 600 t. The most common method of farming is semi-intensive rearing in different types of pond and stocking material ranges from early stage juveniles to berried females. The cost of stocking material is discussed. The water supply and quality varied greatly between farms. Water quality parameters such as temperature, calcium and metal concentrations and the occurrence of nitrogen compounds in the water are discussed as are various methods of water management, feed composition and the occurrence of macrophytes in the ponds. Diseases apart from crayfish plague, Aphanomyces astaci, are not normally a problem. The most common predators were mink and heron, but farmers also named other mammals and birds as well as amphibians, insects and snakes. The yield of noble crayfish varied from 60 to 430 kg and for signal crayfish from 50 to 680 kg per ha and year. In 1995 the actual yield of cultured noble crayfish was 12.3 t and 41.7 t of signal crayfish. This was more than 10% of the total crayfish yield in Sweden.