Phases of the ontogenesis of the Mušov Reservoir of the waterwork Nové Mlýny - fish yield and condition parameters of silver bream (Blicca bjoerkna)

Abstract

Overall yields of the carp and of the non-preferred group of coarse "other fish" exhibited in the Mušovská nádrž Reservoir (Fishing ground MRS Dyje 7) significant changes during 1981-2001. The decrease of yield during 1996-1999 is significantly correlated with a decreased fishing pressure (number of fishing visits per year and hectare of fishing ground) while it insignificantly correlates with the quantity of annually stocked carps. The length/weight relationship of the silver bream, if comparing the values from 1980 with those from 1996, exhibit a significant drop. It was concluded, that the reservoir is actually in a phase of stabilised production and characteristic by a feeding competition between the carp as a preffered game fish and the coarse fishes. Also an increased predation by wells exhibited on the non-predatory fishes including the stocked carp can not be excluded