Economic effectiveness of pike (Esox lucius L.) stocking based on the example of selected lakes in East European Plain with consideration of their natural conditons

The aim of the study was to assess the economic effectiveness of pike (Esox lucius L.) stocking based on the value of fish caught with commercial fishing gears and the value of stocking material introduced into 44 lakes in the Ełk Lake District in northeastern Poland. The effectiveness of stocking is presented against the background of lake environmental conditions in the context of their natural potential for pike populations to inhabit and develop in them. The data analyzed regarded the size and value of catches and stocking from 1996-2017 that was obtained from an entity authorized to exploit fisheries. Information on selected lake morphometric, morphological, and environmental parameters was also obtained from this source. The value of pike catches in the analyzed period was characterized by a high, stabile level, and the stocking level increased. The indicator of the stocking economic effectiveness was at a high average annual level in excess of 3.9 PLN of catches per 1.0 PLN for stocking, but it decreased during the period analyzed. The high stocking effectiveness in the studied lakes was determined by, inter alia, natural conditions, stocking material quality, properly performed stocking, and efficient exploitation. However, it can be concluded that it is mainly stocking that maintains pike catches at a high, relatively stable level in the lakes analyzed. Additionally, new methods of pike population management are discussed, e.g., catch and release.