Economic effectiveness of stocking lakes in Poland

Survey data regarding stocking and fish catches from the 1995-2007 period was collected from enterprises licensed to manage lake fisheries in Poland. An average of 70 questionnaires were collected annually from lake fisheries enterprises exploiting a combined lake surface area of 228,102 ha. Many species of fish analyzed were those that were the most intensely stocked. The effectiveness of stocking in Polish lakes in this period was analyzed by calculating the mean annual stocking effectiveness coefficient, i.e, the value in PLN/ha of catches of a given species per 1 PLN/ha of stocking this species in a given year. The highest mean annual stocking effectiveness coefficient was noted for pikeperch Sander lucioperca (L.) (4.21 PLN/ha) and bighead carp Aristichthys noblilis Rich. together with silver carp Hypophthalmichthys molitrix Val. (4.02 PLN/ha); however, these values were unstable. A similar situation was noted for eel Anguilla anguilla (L.), which had the next highest stocking effectiveness coefficient at 2.32 PLN/ ha. The stocking effectiveness coefficient was stable for tench Tinca tinca (L.) (2.16 PLN/ha), vendace Coregonus albula (L.) (2.09 PLN/ha), and pike Esox lucius L. (1.31 PLN/ha). The stocking of whitefish Coregonus lavaretus (L.), Wels catfish Silurus glanis (L.), crucian carp Carassius carassius (L.) together with Prussian carp Carassius auratus gibelio Bloch., common carp Cyprinus carpio L., and grass carp Ctenopharyngodon idella Val., were ineffective economically from the viewpoint of the size of commercial catches.