Effectiveness of coregonid management versus environment quality

Abstract

Coregonid management was analysed with consideration given to some parameters of environment quality and a ranking system used since 1982 to estimate lake quality. The study comprised 38 lakes, for which catch statistics and management data were collected, embracing a period of 27 years (1968-1994). The lakes were analysed as a whole sample and divided to two groups: „good" and „bad" quality. The latter division was based on the mean rank calculated for the whole sample, amounting to 2.273. Statistically significant differences were found in the two groups. Commercial yields of vendace did not depend on the analysed environment quality parameters, but effectiveness of vendace stockings decreased with increasing lake trophy measured as chlorophyll content in the surface water layer. Yield of whitefish depended on total nitrogen and total phosphorus content in water, with phosphorus having a stimulating and nitrogen a limiting effect. The results of coregonid management have been discussed in relation to environment quality.