Effectiveness of coregonid management on the background of fish yield changes in 25 Polish lakes

Abstract

Analyses were performed of 33-year data on fish catches and coregonid management in 25 lakes of total area over 25 thousand ha, in which the fish stock had undergone significant changes under the effect of eutrophication. Time series was taken advantage of to determine the character and rate of these changes in the whole stock of lake fish, with special attention given to three economically valuable species: whitefish, vendace and pike-perch. The analyses embraced also the effectiveness of stocking with coregonids. Mutual economic relations were examined between catches of coregonids and those of pike-perch. Practical implications of the results in the decision-making process have been discussed.